Updates build to version 0.4.0 alpha 4

405 Airspy Spectrum/Waterfall Freezes

.idea/dictionaries/denny.xml

@@ -0,0 +1,32 @@
+<component name="ProjectDictionaryState">
+  <dictionary name="denny">
+    <words>
+      <w>bahroo</w>
+      <w>broadcastify</w>
+      <w>correlator</w>
+      <w>dinf</w>
+      <w>esnid</w>
+      <w>fleetsync</w>
+      <w>heterdyned</w>
+      <w>heterodynes</w>
+      <w>icecast</w>
+      <w>ident</w>
+      <w>nutall</w>
+      <w>overflowable</w>
+      <w>polyphase</w>
+      <w>qpsk</w>
+      <w>remez</w>
+      <w>resampler</w>
+      <w>samplerate</w>
+      <w>sdrtrunk</w>
+      <w>sheirer</w>
+      <w>shoutcast</w>
+      <w>streamable</w>
+      <w>talkgroup</w>
+      <w>tgid</w>
+      <w>ultravox</w>
+      <w>wacn</w>
+      <w>xtea</w>
+    </words>
+  </dictionary>
+</component>

.idea/libraries/imports.xml

@@ -0,0 +1,14 @@
+<component name="libraryTable">
+  <library name="imports">
+    <CLASSES>
+      <root url="jar://$PROJECT_DIR$/imports/jmbe-interface-0.3.3.jar!/" />
+      <root url="jar://$PROJECT_DIR$/imports/java-lame-3.98.4.jar!/" />
+      <root url="jar://$PROJECT_DIR$/imports/radioreference-14.jar!/" />
+      <root url="jar://$PROJECT_DIR$/imports/wsdl4j-1.5.1.jar!/" />
+      <root url="jar://$PROJECT_DIR$/imports/commons-math3-3.6.1.jar!/" />
+      <root url="jar://$PROJECT_DIR$/imports/libresample4j-0.1.3.jar!/" />
+    </CLASSES>
+    <JAVADOC />
+    <SOURCES />
+  </library>
+</component>

.idea/misc.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_8" default="true" project-jdk-name="1.8" project-jdk-type="JavaSDK">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_8" default="false" project-jdk-name="1.8" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/out" />
   </component>
 </project>

.idea/vcs.xml

@@ -1,5 +1,15 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
+  <component name="IssueNavigationConfiguration">
+    <option name="links">
+      <list>
+        <IssueNavigationLink>
+          <option name="issueRegexp" value="#(\d+)" />
+          <option name="linkRegexp" value="https://github.com/DSheirer/sdrtrunk/issues/$1" />
+        </IssueNavigationLink>
+      </list>
+    </option>
+  </component>
   <component name="VcsDirectoryMappings">
     <mapping directory="$PROJECT_DIR$" vcs="Git" />
   </component>

CHANGELOG

@@ -1,4 +1,5 @@
-0.3.4 20180210
+0.3.4 20180418
+ - New P25 C4FM decoder that uses Differential QPSK decoder instead of FM demodulation with 4FSK.
  - Adds channel auto-start and ordering capability with startup dialog allowing user to invoke or bypass channel
    auto-start.  Provides user with more control over startup configuration.
  - Adds preferred tuner attribute to channel configuration allowing user to select a preferred tuner for the channel

build.gradle

@@ -15,7 +15,7 @@ repositories {
     mavenCentral()
 }
 
-version = '0.3.4-beta.1'
+version = '0.4.0-alpha.4'
 sourceCompatibility = 1.8
 
 sourceSets {

copyright_header.txt

@@ -1,17 +0,0 @@
-/*******************************************************************************
- *     SDR Trunk 
- *     Copyright (C) 2014-2016 Dennis Sheirer
- * 
- *     This program is free software: you can redistribute it and/or modify
- *     it under the terms of the GNU General Public License as published by
- *     the Free Software Foundation, either version 3 of the License, or
- *     (at your option) any later version.
- * 
- *     This program is distributed in the hope that it will be useful,
- *     but WITHOUT ANY WARRANTY; without even the implied warranty of
- *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *     GNU General Public License for more details.
- * 
- *     You should have received a copy of the GNU General Public License
- *     along with this program.  If not, see <http://www.gnu.org/licenses/>
- ******************************************************************************/

sdrtrunk.iml

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module type="JAVA_MODULE" version="4">
+  <component name="NewModuleRootManager" inherit-compiler-output="true">
+    <exclude-output />
+    <content url="file://$MODULE_DIR$">
+      <sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/images" type="java-resource" />
+      <sourceFolder url="file://$MODULE_DIR$/config" type="java-resource" />
+    </content>
+    <orderEntry type="inheritedJdk" />
+    <orderEntry type="sourceFolder" forTests="false" />
+    <orderEntry type="library" name="imports" level="project" />
+  </component>
+</module>

src/main/java/io/github/dsheirer/audio/AudioManager.java

@@ -24,6 +24,7 @@ import io.github.dsheirer.audio.output.StereoAudioOutput;
 import io.github.dsheirer.properties.SystemProperties;
 import io.github.dsheirer.sample.Broadcaster;
 import io.github.dsheirer.sample.Listener;
+import io.github.dsheirer.sample.buffer.ReusableAudioPacket;
 import io.github.dsheirer.source.mixer.MixerChannel;
 import io.github.dsheirer.source.mixer.MixerChannelConfiguration;
 import io.github.dsheirer.source.mixer.MixerManager;
@@ -43,7 +44,7 @@ import java.util.concurrent.LinkedTransferQueue;
 import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.TimeUnit;
 
-public class AudioManager implements Listener<AudioPacket>, IAudioController
+public class AudioManager implements Listener<ReusableAudioPacket>, IAudioController
 {
     private static final Logger mLog = LoggerFactory.getLogger(AudioManager.class);
 
@@ -58,7 +59,7 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
     public static final AudioEvent CONFIGURATION_CHANGE_COMPLETE =
         new AudioEvent(AudioEvent.Type.AUDIO_CONFIGURATION_CHANGE_COMPLETE, null);
 
-    private LinkedTransferQueue<AudioPacket> mAudioPacketQueue = new LinkedTransferQueue<>();
+    private LinkedTransferQueue<ReusableAudioPacket> mAudioPacketQueue = new LinkedTransferQueue<>();
     private Map<Integer,AudioOutputConnection> mChannelConnectionMap = new HashMap<>();
     private List<AudioOutputConnection> mAudioOutputConnections = new ArrayList<>();
     private AudioOutputConnection mLowestPriorityConnection;
@@ -170,7 +171,7 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
      * Primary ingest point for audio produced by all decoding channels, for distribution to audio playback devices.
      */
     @Override
-    public synchronized void receive(AudioPacket packet)
+    public synchronized void receive(ReusableAudioPacket packet)
     {
         mAudioPacketQueue.add(packet);
     }
@@ -362,7 +363,7 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
      * @param audioPacket from a decoding channel source
      * @return an audio output connection or null
      */
-    private AudioOutputConnection getConnection(AudioPacket audioPacket)
+    private AudioOutputConnection getConnection(ReusableAudioPacket audioPacket)
     {
         int channelMetadataID = audioPacket.getMetadata().getMetadataID();
 
@@ -410,6 +411,8 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
 
     public class AudioPacketProcessor implements Runnable
     {
+        private List<ReusableAudioPacket> mPackets = new ArrayList<>();
+
         @Override
         public void run()
         {
@@ -419,14 +422,12 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
 
                 if(mAudioPacketQueue != null)
                 {
-                    List<AudioPacket> packets = new ArrayList<AudioPacket>();
+                    mAudioPacketQueue.drainTo(mPackets);
 
-                    mAudioPacketQueue.drainTo(packets);
-
-                    for(AudioPacket packet : packets)
+                    for(ReusableAudioPacket packet : mPackets)
                     {
                         /* Don't process any packet's marked as do not monitor */
-                        if(!packet.getMetadata().isDoNotMonitor() && packet.getType() == AudioPacket.Type.AUDIO)
+                        if(!packet.getMetadata().isDoNotMonitor() && packet.getType() == ReusableAudioPacket.Type.AUDIO)
                         {
                             AudioOutputConnection connection = getConnection(packet);
 
@@ -434,13 +435,29 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
                             {
                                 connection.receive(packet);
                             }
+                            else
+                            {
+                                packet.decrementUserCount();
+                            }
+                        }
+                        else
+                        {
+                            packet.decrementUserCount();
                         }
                     }
+
+                    mPackets.clear();
                 }
             }
             catch(Exception e)
             {
                 mLog.error("Encountered error while processing audio packets", e);
+
+                while(mPackets.size() > 0)
+                {
+                    ReusableAudioPacket audioPacket = mPackets.remove(0);
+                    audioPacket.decrementUserCount();
+                }
             }
         }
     }
@@ -463,7 +480,7 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
             mAudioOutput = audioOutput;
         }
 
-        public void receive(AudioPacket packet)
+        public void receive(ReusableAudioPacket packet)
         {
             if(packet.hasMetadata() && packet.getMetadata().getMetadataID() == mChannelMetadataID)
             {

src/main/java/io/github/dsheirer/audio/AudioModule.java

@@ -1,19 +1,16 @@
 /*******************************************************************************
- * sdrtrunk
- * Copyright (C) 2014-2017 Dennis Sheirer
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
  *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
  *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
  *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
  *
  ******************************************************************************/
 package io.github.dsheirer.audio;
@@ -23,92 +20,80 @@ import io.github.dsheirer.audio.squelch.SquelchState;
 import io.github.dsheirer.channel.metadata.Metadata;
 import io.github.dsheirer.dsp.filter.design.FilterDesignException;
 import io.github.dsheirer.dsp.filter.fir.FIRFilterSpecification;
+import io.github.dsheirer.dsp.filter.fir.real.RealFIRFilter2;
 import io.github.dsheirer.dsp.filter.fir.remez.RemezFIRFilterDesigner;
-import io.github.dsheirer.dsp.filter.polyphase.PolyphaseFIRDecimatingFilter_RB;
 import io.github.dsheirer.module.Module;
 import io.github.dsheirer.sample.Listener;
-import io.github.dsheirer.sample.real.IFilteredRealBufferListener;
-import io.github.dsheirer.sample.real.RealBuffer;
+import io.github.dsheirer.sample.buffer.IReusableBufferListener;
+import io.github.dsheirer.sample.buffer.ReusableAudioPacket;
+import io.github.dsheirer.sample.buffer.ReusableAudioPacketQueue;
+import io.github.dsheirer.sample.buffer.ReusableFloatBuffer;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.util.concurrent.ScheduledExecutorService;
-
 /**
- * Provides packaging of demodulated audio sample buffers into audio packets for
- * broadcast to registered audio packet listeners.  Includes audio packet
- * metadata in constructed audio packets.
+ * Provides packaging of demodulated audio sample buffers into audio packets for broadcast to registered audio packet
+ * listeners.  Includes audio packet metadata in constructed audio packets.
  *
- * Incorporates audio squelch state listener to control if audio packets are
- * broadcast or ignored.
+ * Incorporates audio squelch state listener to control if audio packets are broadcast or ignored.
+ *
+ * This class is designed to support 8 kHz sample rate demodulated audio.
  */
-public class AudioModule extends Module implements IAudioPacketProvider, IFilteredRealBufferListener,
-    ISquelchStateListener, Listener<RealBuffer>
+public class AudioModule extends Module implements IAudioPacketProvider, IReusableBufferListener,
+    ISquelchStateListener, Listener<ReusableFloatBuffer>
 {
     protected static final Logger mLog = LoggerFactory.getLogger(AudioModule.class);
+    private ReusableAudioPacketQueue mAudioPacketQueue = new ReusableAudioPacketQueue("AudioModule");
 
-    private static float[] mDecimationCoefficients;
+    private static float[] sHighPassFilterCoefficients;
 
     static
     {
-        //Band-pass filter to both decimate (48kHz to 8kHz) and block 0 - 300 Hz (LTR signalling).
-        FIRFilterSpecification specification = FIRFilterSpecification.bandPassBuilder()
-            .sampleRate(48000)
-            .stopFrequency1(150)
-            .passFrequencyBegin(300)
-            .passFrequencyEnd(3500)
-            .stopFrequency2(4000)
-            .stopRipple(0.0004)
-            .passRipple(0.008)
+        FIRFilterSpecification specification = FIRFilterSpecification.highPassBuilder()
+            .sampleRate(8000)
+            .stopBandCutoff(200)
+            .stopBandAmplitude(0.0)
+            .stopBandRipple(0.025)
+            .passBandStart(300)
+            .passBandAmplitude(1.0)
+            .passBandRipple(0.01)
             .build();
-
-        RemezFIRFilterDesigner designer = new RemezFIRFilterDesigner(specification);
-
         try
         {
-            if(!designer.isValid())
-            {
-                throw new FilterDesignException("Couldn't design the audio decimation filter");
-            }
+            RemezFIRFilterDesigner designer = new RemezFIRFilterDesigner(specification);
 
-            mDecimationCoefficients = designer.getImpulseResponse();
+            if(designer.isValid())
+            {
+                sHighPassFilterCoefficients = designer.getImpulseResponse();
+            }
         }
-        catch(FilterDesignException e)
+        catch(FilterDesignException fde)
         {
-            mLog.debug("Error designing filter", e);
+            mLog.error("Filter design error", fde);
         }
     }
 
+    private RealFIRFilter2 mHighPassFilter = new RealFIRFilter2(sHighPassFilterCoefficients);
     private SquelchStateListener mSquelchStateListener = new SquelchStateListener();
     private SquelchState mSquelchState = SquelchState.SQUELCH;
-    private Listener<AudioPacket> mAudioPacketListener;
-    private PolyphaseFIRDecimatingFilter_RB mAudioDecimationFilter;
+    private Listener<ReusableAudioPacket> mAudioPacketListener;
     private Metadata mMetadata;
 
+    /**
+     * Creates an Audio Module.
+     *
+     * @param metadata to use for audio packets produced by this audio module.
+     */
     public AudioModule(Metadata metadata)
     {
         mMetadata = metadata;
-
-        mAudioDecimationFilter = new PolyphaseFIRDecimatingFilter_RB(mDecimationCoefficients, 6, 2.0f);
-        mAudioDecimationFilter.setListener(new Listener<RealBuffer>()
-        {
-            @Override
-            public void receive(RealBuffer realBuffer)
-            {
-                if(mAudioPacketListener != null)
-                {
-                    AudioPacket packet = new AudioPacket(realBuffer.getSamples(), mMetadata.copyOf());
-                    mAudioPacketListener.receive(packet);
-                }
-            }
-        });
     }
 
     @Override
     public void dispose()
     {
-        mSquelchStateListener = null;
         mAudioPacketListener = null;
+        mSquelchStateListener = null;
     }
 
     @Override
@@ -117,7 +102,7 @@ public class AudioModule extends Module implements IAudioPacketProvider, IFilter
     }
 
     @Override
-    public void start(ScheduledExecutorService executor)
+    public void start()
     {
         /* No start operations provided */
     }
@@ -125,34 +110,18 @@ public class AudioModule extends Module implements IAudioPacketProvider, IFilter
     @Override
     public void stop()
     {
-        /* Issue an end audio packet in case a recorder is still rolling */
+        /* Issue an end-audio packet in case a recorder is still rolling */
         if(mAudioPacketListener != null)
         {
-            mAudioPacketListener.receive(new AudioPacket(AudioPacket.Type.END, mMetadata.copyOf()));
-        }
-    }
-
-    /**
-     * Processes demodulated audio samples into audio packets with current audio
-     * metadata and sends to the registered listener
-     */
-    @Override
-    public void receive(RealBuffer buffer)
-    {
-        if(mAudioPacketListener != null && mSquelchState == SquelchState.UNSQUELCH)
-        {
-            mAudioDecimationFilter.receive(buffer);
+            ReusableAudioPacket endAudioPacket = mAudioPacketQueue.getEndAudioBuffer();
+            endAudioPacket.setMetadata(mMetadata.copyOf());
+            endAudioPacket.incrementUserCount();
+            mAudioPacketListener.receive(endAudioPacket);
         }
     }
 
     @Override
-    public Listener<RealBuffer> getFilteredRealBufferListener()
-    {
-        return this;
-    }
-
-    @Override
-    public void setAudioPacketListener(Listener<AudioPacket> listener)
+    public void setAudioPacketListener(Listener<ReusableAudioPacket> listener)
     {
         mAudioPacketListener = listener;
     }
@@ -169,6 +138,34 @@ public class AudioModule extends Module implements IAudioPacketProvider, IFilter
         return mSquelchStateListener;
     }
 
+    @Override
+    public void receive(ReusableFloatBuffer reusableFloatBuffer)
+    {
+        if(mAudioPacketListener != null && mSquelchState == SquelchState.UNSQUELCH)
+        {
+            ReusableFloatBuffer highPassFiltered = mHighPassFilter.filter(reusableFloatBuffer);
+
+            ReusableAudioPacket audioPacket = mAudioPacketQueue.getBuffer(highPassFiltered.getSampleCount());
+            audioPacket.loadAudioFrom(highPassFiltered);
+            audioPacket.setMetadata(mMetadata.copyOf());
+
+            mAudioPacketListener.receive(audioPacket);
+
+            highPassFiltered.decrementUserCount();
+        }
+        else
+        {
+            reusableFloatBuffer.decrementUserCount();
+        }
+    }
+
+    @Override
+    public Listener getReusableBufferListener()
+    {
+        //Redirect received reusable buffers to the receive(buffer) method
+        return this;
+    }
+
     /**
      * Wrapper for squelch state listener
      */
@@ -179,7 +176,9 @@ public class AudioModule extends Module implements IAudioPacketProvider, IFilter
         {
             if(state == SquelchState.SQUELCH && mAudioPacketListener != null)
             {
-                mAudioPacketListener.receive(new AudioPacket(AudioPacket.Type.END, mMetadata.copyOf()));
+                ReusableAudioPacket endAudioPacket = mAudioPacketQueue.getEndAudioBuffer();
+                endAudioPacket.setMetadata(mMetadata.copyOf());
+                mAudioPacketListener.receive(endAudioPacket);
             }
 
             mSquelchState = state;

src/main/java/io/github/dsheirer/audio/AudioPacket.java

@@ -1,78 +0,0 @@
-/*******************************************************************************
- * sdrtrunk
- * Copyright (C) 2014-2017 Dennis Sheirer
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>
- *
- ******************************************************************************/
-package io.github.dsheirer.audio;
-
-import io.github.dsheirer.channel.metadata.Metadata;
-import io.github.dsheirer.sample.real.RealBuffer;
-
-public class AudioPacket
-{
-    private Type mType;
-    private RealBuffer mAudioData;
-    private Metadata mMetadata;
-
-    public AudioPacket(Type type, Metadata metadata)
-    {
-        mType = type;
-        mMetadata = metadata;
-    }
-
-    public AudioPacket(float[] audio, Metadata metadata)
-    {
-        this(Type.AUDIO, metadata);
-
-        mAudioData = new RealBuffer(audio);
-    }
-
-    public boolean hasMetadata()
-    {
-        return mMetadata != null;
-    }
-
-    public Metadata getMetadata()
-    {
-        return mMetadata;
-    }
-
-    public void setMetadata(Metadata metadata)
-    {
-        mMetadata = metadata;
-    }
-
-    public Type getType()
-    {
-        return mType;
-    }
-
-    public RealBuffer getAudioBuffer()
-    {
-        return mAudioData;
-    }
-
-    public boolean hasAudioBuffer()
-    {
-        return mAudioData != null;
-    }
-
-    public enum Type
-    {
-        AUDIO,
-        END;
-    }
-}

src/main/java/io/github/dsheirer/audio/AudioPacketRateCounter.java

@@ -1,55 +0,0 @@
-package io.github.dsheirer.audio;
-
-import io.github.dsheirer.sample.Listener;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-public class AudioPacketRateCounter implements Listener<AudioPacket>
-{
-	private final static Logger mLog = 
-			LoggerFactory.getLogger( AudioPacketRateCounter.class );
-
-	private Listener<AudioPacket> mListener;
-	private long mCount;
-	private long mStartTime = -1;
-	
-	private String mName;
-	
-	public AudioPacketRateCounter()
-	{
-		mName = "UNNAMED";
-	}
-	
-	public AudioPacketRateCounter( String name )
-	{
-		mName = name;
-	}
-	
-	@Override
-	public void receive( AudioPacket packet )
-	{
-		if( mStartTime == -1 )
-		{
-			mStartTime = System.currentTimeMillis();
-		}
-		
-		mCount += packet.getAudioBuffer().getSamples().length;
-
-		long elapsed = System.currentTimeMillis() - mStartTime;
-		
-		if( elapsed != 0 )
-		{
-			mLog.debug( "[" + mName + "] Audio Rate: " + ( mCount / elapsed ) + " kHz" );
-		}
-		
-		if( mListener != null )
-		{
-			mListener.receive( packet );
-		}
-	}
-	
-	public void setListener( Listener<AudioPacket> listener )
-	{
-		mListener = listener;
-	}
-}

src/main/java/io/github/dsheirer/audio/AudioPanel.java

@@ -53,8 +53,8 @@ public class AudioPanel extends JPanel implements Listener<AudioEvent>
 
     private static final Logger mLog = LoggerFactory.getLogger(AudioPanel.class);
 
-    private static ImageIcon MUTED_ICON = IconManager.getScaledIcon("/images/audio_muted.png", 20);
-    private static ImageIcon UNMUTED_ICON = IconManager.getScaledIcon("/images/audio_unmuted.png", 20);
+    private static ImageIcon MUTED_ICON = IconManager.getScaledIcon("images/audio_muted.png", 20);
+    private static ImageIcon UNMUTED_ICON = IconManager.getScaledIcon("images/audio_unmuted.png", 20);
 
     private IconManager mIconManager;
     private SettingsManager mSettingsManager;

src/main/java/io/github/dsheirer/audio/AudioUtils.java

@@ -1,24 +1,22 @@
 /*******************************************************************************
- * sdrtrunk
- * Copyright (C) 2014-2016 Dennis Sheirer
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
  *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
  *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
  *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
  *
  ******************************************************************************/
 package io.github.dsheirer.audio;
 
 import io.github.dsheirer.sample.ConversionUtils;
+import io.github.dsheirer.sample.buffer.ReusableAudioPacket;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -34,17 +32,18 @@ public class AudioUtils
     /**
      * Converts the audio packets into a byte array of 16-bit, little-endian audio samples
      */
-    public static byte[] convertTo16BitSamples(List<AudioPacket> audioPackets)
+    public static byte[] convertTo16BitSamples(List<ReusableAudioPacket> audioPackets)
     {
         ByteArrayOutputStream stream = new ByteArrayOutputStream();
 
         try
         {
-            for(AudioPacket packet: audioPackets)
+            for(ReusableAudioPacket audioPacket: audioPackets)
             {
                 //Converting from 32-bit floats to signed 16-bit samples
-                ByteBuffer buffer = ConversionUtils.convertToSigned16BitSamples(packet.getAudioBuffer().getSamples());
+                ByteBuffer buffer = ConversionUtils.convertToSigned16BitSamples(audioPacket.getAudioSamples());
                 stream.write(buffer.array());
+                audioPacket.decrementUserCount();
             }
         }
         catch(IOException e)

src/main/java/io/github/dsheirer/audio/IAudioPacketListener.java

@@ -1,8 +1,9 @@
 package io.github.dsheirer.audio;
 
 import io.github.dsheirer.sample.Listener;
+import io.github.dsheirer.sample.buffer.ReusableAudioPacket;
 
 public interface IAudioPacketListener
 {
-	public Listener<AudioPacket> getAudioPacketListener();
+	public Listener<ReusableAudioPacket> getAudioPacketListener();
 }

src/main/java/io/github/dsheirer/audio/IAudioPacketProvider.java

@@ -1,9 +1,10 @@
 package io.github.dsheirer.audio;
 
 import io.github.dsheirer.sample.Listener;
+import io.github.dsheirer.sample.buffer.ReusableAudioPacket;
 
 public interface IAudioPacketProvider
 {
-	public void setAudioPacketListener( Listener<AudioPacket> listener );
+	public void setAudioPacketListener( Listener<ReusableAudioPacket> listener );
 	public void removeAudioPacketListener();
 }

src/main/java/io/github/dsheirer/audio/broadcast/AudioBroadcaster.java

@@ -245,7 +245,11 @@ public abstract class AudioBroadcaster implements Listener<AudioRecording>
     {
         if(mBroadcastState != state)
         {
-            mLog.info("[" + getStreamName() + "] status: " + state);
+            if(state == BroadcastState.CONNECTED || state == BroadcastState.DISCONNECTED)
+            {
+                mLog.info("[" + getStreamName() + "] status: " + state);
+            }
+
             mBroadcastState = state;
 
             broadcast(new BroadcastEvent(this, BroadcastEvent.Event.BROADCASTER_STATE_CHANGE));

src/main/java/io/github/dsheirer/audio/broadcast/BroadcastModel.java

@@ -19,12 +19,12 @@
 package io.github.dsheirer.audio.broadcast;
 
 import io.github.dsheirer.alias.id.broadcast.BroadcastChannel;
-import io.github.dsheirer.audio.AudioPacket;
 import io.github.dsheirer.channel.metadata.Metadata;
 import io.github.dsheirer.icon.IconManager;
 import io.github.dsheirer.properties.SystemProperties;
 import io.github.dsheirer.sample.Broadcaster;
 import io.github.dsheirer.sample.Listener;
+import io.github.dsheirer.sample.buffer.ReusableAudioPacket;
 import io.github.dsheirer.util.ThreadPool;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -46,7 +46,7 @@ import java.util.function.Consumer;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
-public class BroadcastModel extends AbstractTableModel implements Listener<AudioPacket>
+public class BroadcastModel extends AbstractTableModel implements Listener<ReusableAudioPacket>
 {
     private final static Logger mLog = LoggerFactory.getLogger(BroadcastModel.class);
 
@@ -276,7 +276,7 @@ public class BroadcastModel extends AbstractTableModel implements Listener<Audio
     }
 
     @Override
-    public void receive(AudioPacket audioPacket)
+    public void receive(ReusableAudioPacket audioPacket)
     {
         if(audioPacket.hasMetadata() && audioPacket.getMetadata().isStreamable())
         {
@@ -284,11 +284,14 @@ public class BroadcastModel extends AbstractTableModel implements Listener<Audio
             {
                 if(mBroadcasterMap.containsKey(channel.getChannelName()))
                 {
+                    audioPacket.incrementUserCount();
                     mStreamManager.receive(audioPacket);
                     return;
                 }
             }
         }
+
+        audioPacket.decrementUserCount();
     }
 
     /**

src/main/java/io/github/dsheirer/audio/broadcast/BroadcastState.java

@@ -70,6 +70,11 @@ public enum BroadcastState
      */
     MOUNT_POINT_IN_USE("Mount Point In Use", false),
 
+    /**
+     * Network is unavailable or the server address cannot be resolved
+     */
+    NETWORK_UNAVAILABLE("Network Unavailable", false),
+
     /**
      * Server is not known or reachable
      */

src/main/java/io/github/dsheirer/audio/broadcast/BroadcastStatusPanel.java

@@ -20,9 +20,14 @@ package io.github.dsheirer.audio.broadcast;
 
 import net.miginfocom.swing.MigLayout;
 
-import javax.swing.*;
+import javax.swing.JLabel;
+import javax.swing.JPanel;
+import javax.swing.JScrollPane;
+import javax.swing.JTable;
+import javax.swing.SwingConstants;
 import javax.swing.table.DefaultTableCellRenderer;
-import java.awt.*;
+import java.awt.Color;
+import java.awt.Component;
 
 public class BroadcastStatusPanel extends JPanel
 {
@@ -96,7 +101,8 @@ public class BroadcastStatusPanel extends JPanel
                         setBackground(table.getBackground());
                         setForeground(Color.LIGHT_GRAY);
                     }
-                    else if(state == BroadcastState.INVALID_SETTINGS)
+                    else if(state == BroadcastState.INVALID_SETTINGS ||
+                            state == BroadcastState.NETWORK_UNAVAILABLE)
                     {
                         setBackground(Color.YELLOW);
                         setForeground(table.getForeground());

src/main/java/io/github/dsheirer/audio/broadcast/StreamManager.java

@@ -18,9 +18,9 @@
  ******************************************************************************/
 package io.github.dsheirer.audio.broadcast;
 
-import io.github.dsheirer.audio.AudioPacket;
 import io.github.dsheirer.record.AudioRecorder;
 import io.github.dsheirer.sample.Listener;
+import io.github.dsheirer.sample.buffer.ReusableAudioPacket;
 import io.github.dsheirer.util.ThreadPool;
 import io.github.dsheirer.util.TimeStamp;
 import org.slf4j.Logger;
@@ -37,7 +37,7 @@ import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 
-public class StreamManager implements Listener<AudioPacket>
+public class StreamManager implements Listener<ReusableAudioPacket>
 {
     private final static Logger mLog = LoggerFactory.getLogger(StreamManager.class);
     private static final long MAXIMUM_RECORDER_LIFESPAN_MILLIS = 30000; //30 seconds
@@ -115,7 +115,7 @@ public class StreamManager implements Listener<AudioPacket>
     }
 
     @Override
-    public void receive(AudioPacket audioPacket)
+    public void receive(ReusableAudioPacket audioPacket)
     {
         if(mRunning.get() && audioPacket.hasMetadata())
         {
@@ -123,9 +123,9 @@ public class StreamManager implements Listener<AudioPacket>
             {
                 int channelMetadataID = audioPacket.getMetadata().getMetadataID();
 
-                AudioPacket.Type type = audioPacket.getType();
+                ReusableAudioPacket.Type type = audioPacket.getType();
 
-                if(type == AudioPacket.Type.AUDIO)
+                if(type == ReusableAudioPacket.Type.AUDIO)
                 {
                     if(mStreamRecorders.containsKey(channelMetadataID))
                     {
@@ -133,6 +133,7 @@ public class StreamManager implements Listener<AudioPacket>
 
                         if(recorder != null)
                         {
+                            audioPacket.incrementUserCount();
                             recorder.receive(audioPacket);
                         }
                     }
@@ -140,12 +141,13 @@ public class StreamManager implements Listener<AudioPacket>
                     {
                         AudioRecorder recorder = BroadcastFactory.getAudioRecorder(getTemporaryRecordingPath(),
                             mBroadcastFormat);
-                        recorder.start(ThreadPool.SCHEDULED);
+                        recorder.start();
+                        audioPacket.incrementUserCount();
                         recorder.receive(audioPacket);
                         mStreamRecorders.put(channelMetadataID, recorder);
                     }
                 }
-                else if(type == AudioPacket.Type.END)
+                else if(type == ReusableAudioPacket.Type.END)
                 {
                     removeRecorder(channelMetadataID);
                 }
@@ -155,6 +157,8 @@ public class StreamManager implements Listener<AudioPacket>
                 }
             }
         }
+
+        audioPacket.decrementUserCount();
     }
 
     /**

src/main/java/io/github/dsheirer/audio/broadcast/icecast/IcecastBroadcastMetadataUpdater.java

@@ -22,6 +22,7 @@ import io.github.dsheirer.audio.broadcast.IBroadcastMetadataUpdater;
 import io.github.dsheirer.channel.metadata.Metadata;
 import io.github.dsheirer.properties.SystemProperties;
 import io.github.dsheirer.util.ThreadPool;
+import org.apache.mina.core.RuntimeIoException;
 import org.apache.mina.core.future.ConnectFuture;
 import org.apache.mina.core.service.IoHandlerAdapter;
 import org.apache.mina.core.session.IoSession;
@@ -35,7 +36,6 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.io.UnsupportedEncodingException;
-import java.net.ConnectException;
 import java.net.InetSocketAddress;
 import java.net.URLEncoder;
 import java.nio.channels.UnresolvedAddressException;
@@ -117,70 +117,64 @@ public class IcecastBroadcastMetadataUpdater implements IBroadcastMetadataUpdate
     {
         mMetadataQueue.offer(getSong(metadata));
 
-        if(mUpdating.compareAndSet(false, true))
+        if(!mUpdating.get() && !mMetadataQueue.isEmpty())
         {
-            String song = mMetadataQueue.poll();
-
-            while(song != null)
+            Runnable runnable =  new Runnable()
             {
-                HttpRequest updateRequest = createUpdateRequest(song);
-
-                if(updateRequest != null)
+                @Override
+                public void run()
                 {
-                    ThreadPool.SCHEDULED.schedule(new Runnable()
+                    if(!mMetadataQueue.isEmpty() && mUpdating.compareAndSet(false, true))
                     {
-                        @Override
-                        public void run()
+                        try
                         {
-                            try
-                            {
-                                ConnectFuture connectFuture = getSocketConnector()
-                                    .connect(new InetSocketAddress(mIcecastConfiguration.getHost(),
-                                        mIcecastConfiguration.getPort()));
-                                connectFuture.awaitUninterruptibly();
-                                IoSession session = connectFuture.getSession();
+                            ConnectFuture connectFuture = getSocketConnector()
+                                .connect(new InetSocketAddress(mIcecastConfiguration.getHost(),
+                                    mIcecastConfiguration.getPort()));
+                            connectFuture.awaitUninterruptibly();
+                            IoSession session = connectFuture.getSession();
 
-                                if(session != null)
-                                {
-                                    session.write(updateRequest);
-                                }
-                            }
-                            catch(UnresolvedAddressException uae)
+                            if(session != null)
                             {
-                                //Do nothing - the server is temporarily unavailable
-                            }
-                            catch(Exception e)
-                            {
-                                Throwable throwableCause = e.getCause();
+                                String song = mMetadataQueue.poll();
 
-                                if(throwableCause instanceof ConnectException)
+                                while(song != null)
                                 {
-                                    //Do nothing, the server is unavailable
-                                }
-                                else if(throwableCause instanceof UnresolvedAddressException)
-                                {
-                                    //Do nothing - the server is temporarily unavailable
-                                }
-                                else
-                                {
-                                    if(!mStackTraceLoggingSuppressed)
+                                    HttpRequest updateRequest = createUpdateRequest(song);
+
+                                    if(updateRequest != null)
                                     {
-                                        mLog.error("Error sending metadata update.  Future errors will " +
-                                            "be suppressed", e);
-
-                                        mStackTraceLoggingSuppressed = true;
+                                        session.write(updateRequest);
                                     }
+
+                                    //Fetch next metadata update to send
+                                    song = mMetadataQueue.poll();
                                 }
+
+                                session.closeNow();
                             }
                         }
-                    }, 0l, TimeUnit.SECONDS);
+                        catch(UnresolvedAddressException | RuntimeIoException ure)
+                        {
+                            //Do nothing - the server is temporarily unavailable
+                        }
+                        catch(Exception e)
+                        {
+                            Throwable throwableCause = e.getCause();
+
+                            if(!mStackTraceLoggingSuppressed)
+                            {
+                                mLog.error("Error sending metadata update.  Future errors will be suppressed", e);
+                                mStackTraceLoggingSuppressed = true;
+                            }
+                        }
+
+                        mUpdating.set(false);
+                    }
                 }
+            };
 
-                //Fetch next metadata update to send
-                song = mMetadataQueue.poll();
-            }
-
-            mUpdating.set(false);
+            ThreadPool.SCHEDULED.schedule(runnable, 0l, TimeUnit.SECONDS);
         }
     }
 

src/main/java/io/github/dsheirer/audio/broadcast/icecast/IcecastTCPAudioBroadcaster.java

@@ -27,15 +27,14 @@ import org.apache.mina.core.RuntimeIoException;
 import org.apache.mina.core.future.ConnectFuture;
 import org.apache.mina.core.service.IoHandlerAdapter;
 import org.apache.mina.core.session.IoSession;
-import org.apache.mina.core.write.WriteTimeoutException;
 import org.apache.mina.filter.codec.ProtocolCodecFilter;
 import org.apache.mina.transport.socket.nio.NioSocketConnector;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.io.IOException;
-import java.net.ConnectException;
 import java.net.InetSocketAddress;
+import java.net.SocketException;
 import java.nio.channels.UnresolvedAddressException;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -46,7 +45,8 @@ public class IcecastTCPAudioBroadcaster extends IcecastAudioBroadcaster
     private final static String TERMINATOR = "\r\n";
     private final static String SEPARATOR = ":";
     private static final long RECONNECT_INTERVAL_MILLISECONDS = 3000; //3 seconds
-    private static final long CONNECTION_ATTEMPT_TIMEOUT = 5000; //5 seconds
+    private static final long CONNECTION_ATTEMPT_TIMEOUT_MILLISECONDS = 5000; //5 seconds
+    private static final int WRITE_TIMEOUT_SECONDS = 5;
 
     private NioSocketConnector mSocketConnector;
     private IoSession mStreamingSession = null;
@@ -101,7 +101,7 @@ public class IcecastTCPAudioBroadcaster extends IcecastAudioBroadcaster
             if(mSocketConnector == null)
             {
                 mSocketConnector = new NioSocketConnector();
-                mSocketConnector.setConnectTimeoutCheckInterval(CONNECTION_ATTEMPT_TIMEOUT);
+                mSocketConnector.getSessionConfig().setWriteTimeout(WRITE_TIMEOUT_SECONDS);
 
 //                LoggingFilter loggingFilter = new LoggingFilter(IcecastTCPAudioBroadcaster.class);
 //                loggingFilter.setMessageSentLogLevel(LogLevel.NONE);
@@ -127,45 +127,41 @@ public class IcecastTCPAudioBroadcaster extends IcecastAudioBroadcaster
                             .connect(new InetSocketAddress(getBroadcastConfiguration().getHost(),
                                 getBroadcastConfiguration().getPort()));
 
-                        boolean connected = future.await(CONNECTION_ATTEMPT_TIMEOUT, TimeUnit.MILLISECONDS);
+                        boolean connected = future.await(CONNECTION_ATTEMPT_TIMEOUT_MILLISECONDS, TimeUnit.MILLISECONDS);
 
-                        mStreamingSession = future.getSession();
+                        if(connected)
+                        {
+                            mStreamingSession = future.getSession();
+                            mConnecting.set(false);
+                            return;
+                        }
+                    }
+                    catch(RuntimeIoException rioe)
+                    {
+                        if(rioe.getCause() instanceof SocketException)
+                        {
+                            setBroadcastState(BroadcastState.NETWORK_UNAVAILABLE);
+                            mConnecting.set(false);
+                            return;
+                        }
                     }
                     catch(UnresolvedAddressException uae)
                     {
-                        //What do you do with this?  Nothing.
+                        setBroadcastState(BroadcastState.NETWORK_UNAVAILABLE);
+                        mConnecting.set(false);
+                        return;
                     }
-                    catch(InterruptedException ie)
+                    catch(Exception e)
                     {
-                        //We couldn't connect within the timeout period -- disconnect so that we can try again later
-                        disconnect();
-                    }
-                    catch(RuntimeIoException rie)
-                    {
-                        Throwable throwableCause = rie.getCause();
-
-                        if(throwableCause instanceof ConnectException)
-                        {
-                            setBroadcastState(BroadcastState.NO_SERVER);
-                        }
-                        else if(throwableCause != null)
-                        {
-                            setBroadcastState(BroadcastState.ERROR);
-                            mLog.debug("[" + getStreamName() + "] failed to connect", rie);
-                        }
-                        else
-                        {
-                            setBroadcastState(BroadcastState.ERROR);
-                            mLog.debug("[" + getStreamName() + "] failed to connect - no exception is available");
-                        }
-
-                        disconnect();
+                        mLog.error("Error", e);
+                        //Disregard ... we'll disconnect and try again
                     }
                     catch(Throwable t)
                     {
-                        disconnect();
+                        mLog.error("Throwable error caught", t);
                     }
 
+                    disconnect();
                     mConnecting.set(false);
                 }
             };
@@ -188,6 +184,7 @@ public class IcecastTCPAudioBroadcaster extends IcecastAudioBroadcaster
         }
         else
         {
+            setBroadcastState(BroadcastState.DISCONNECTED);
             mLastConnectionAttempt = System.currentTimeMillis();
         }
     }
@@ -263,49 +260,12 @@ public class IcecastTCPAudioBroadcaster extends IcecastAudioBroadcaster
         @Override
         public void exceptionCaught(IoSession session, Throwable cause) throws Exception
         {
-            if(cause instanceof IOException)
-            {
-                IOException ioe = (IOException)cause;
-
-                if(ioe.getMessage() != null)
-                {
-                    String reason = ioe.getMessage();
-
-                    if(connected())
-                    {
-                        disconnect();
-                    }
-                    else if(reason.startsWith("Connection reset"))
-                    {
-                        disconnect();
-                    }
-                    else if(reason.startsWith("Operation timed out"))
-                    {
-                        disconnect();
-                    }
-                    else
-                    {
-                        setBroadcastState(BroadcastState.ERROR);
-                        disconnect();
-                    }
-                }
-                else if(ioe instanceof WriteTimeoutException)
-                {
-                    disconnect();
-                }
-                else
-                {
-                    setBroadcastState(BroadcastState.ERROR);
-                    disconnect();
-                    mLog.error("[" + getStreamName() + "] Unspecified IO error - streaming halted.", cause);
-                }
-            }
-            else
+            if(!(cause instanceof IOException))
             {
                 mLog.error("[" + getStreamName() + "] Broadcast error", cause);
-                setBroadcastState(BroadcastState.ERROR);
-                disconnect();
             }
+
+            disconnect();
         }
 
         @Override

src/main/java/io/github/dsheirer/audio/convert/IAudioConverter.java

@@ -18,7 +18,7 @@
  ******************************************************************************/
 package io.github.dsheirer.audio.convert;
 
-import io.github.dsheirer.audio.AudioPacket;
+import io.github.dsheirer.sample.buffer.ReusableAudioPacket;
 
 import java.util.List;
 
@@ -27,7 +27,7 @@ public interface IAudioConverter
     /**
      * Converts the PCM audio packets to converted audio format.  May produce partial audio frame data.
      */
-    public byte[] convert(List<AudioPacket> audioPackets);
+    public byte[] convert(List<ReusableAudioPacket> audioPackets);
 
     /**
      * Finalizes audio conversion by fully converting any partial frames left in the buffer and returning the

src/main/java/io/github/dsheirer/audio/convert/MP3AudioConverter.java

@@ -19,8 +19,8 @@
 package io.github.dsheirer.audio.convert;
 
 import io.github.dsheirer.audio.AudioFormats;
-import io.github.dsheirer.audio.AudioPacket;
 import io.github.dsheirer.audio.AudioUtils;
+import io.github.dsheirer.sample.buffer.ReusableAudioPacket;
 import net.sourceforge.lame.lowlevel.LameEncoder;
 import net.sourceforge.lame.mp3.Lame;
 import net.sourceforge.lame.mp3.MPEGMode;
@@ -54,7 +54,7 @@ public class MP3AudioConverter implements IAudioConverter
     }
 
     @Override
-    public byte[] convert(List<AudioPacket> audioPackets)
+    public byte[] convert(List<ReusableAudioPacket> audioPackets)
     {
         mMP3Stream.reset();
 

src/main/java/io/github/dsheirer/audio/convert/MP3SilenceGenerator.java

@@ -18,8 +18,9 @@
  ******************************************************************************/
 package io.github.dsheirer.audio.convert;
 
-import io.github.dsheirer.audio.AudioPacket;
 import io.github.dsheirer.record.mp3.MP3Recorder;
+import io.github.dsheirer.sample.buffer.ReusableAudioPacket;
+import io.github.dsheirer.sample.buffer.ReusableAudioPacketQueue;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -33,6 +34,7 @@ public class MP3SilenceGenerator implements ISilenceGenerator
 
     private MP3AudioConverter mGenerator = new MP3AudioConverter(MP3Recorder.MP3_BIT_RATE, MP3Recorder.CONSTANT_BIT_RATE);
     private byte[] mPreviousPartialFrameData;
+    private ReusableAudioPacketQueue mAudioPacketQueue = new ReusableAudioPacketQueue("MP3 Silence Generator");
 
     /**
      * Generates MP3 audio silence frames
@@ -44,9 +46,10 @@ public class MP3SilenceGenerator implements ISilenceGenerator
     public byte[] generate(long duration)
     {
         int length = (int)(duration * 8);   //8000 Hz sample rate
-        float[] silence = new float[length];
-        AudioPacket silencePacket = new AudioPacket(silence, null);
-        List<AudioPacket> silencePackets = new ArrayList<>();
+        ReusableAudioPacket silencePacket = mAudioPacketQueue.getBuffer(length);
+        Arrays.fill(silencePacket.getAudioSamples(), 0.0f);
+
+        List<ReusableAudioPacket> silencePackets = new ArrayList<>();
         silencePackets.add(silencePacket);
 
         byte[] frameData = mGenerator.convert(silencePackets);

src/main/java/io/github/dsheirer/audio/invert/AudioAdapter.java

@@ -20,6 +20,7 @@ package io.github.dsheirer.audio.invert;
 import io.github.dsheirer.dsp.filter.FilterFactory;
 import io.github.dsheirer.dsp.filter.FloatFIRFilter;
 import io.github.dsheirer.dsp.filter.Window.WindowType;
+import io.github.dsheirer.dsp.mixer.IOscillator;
 import io.github.dsheirer.dsp.mixer.Oscillator;
 
 /**
@@ -29,7 +30,7 @@ import io.github.dsheirer.dsp.mixer.Oscillator;
 public class AudioAdapter
 {
 	private static int mGain = 5;
-	private Oscillator mSineWaveGenerator;
+	private IOscillator mSineWaveGenerator;
 	private FloatFIRFilter mPostInversionFilter;
 	private FloatFIRFilter mAudioHighPassFilter;
 	private AudioType mAudioType = AudioType.NORMAL;
@@ -88,7 +89,7 @@ public class AudioAdapter
 			default:
 				retVal = (float)( mPostInversionFilter.get( 
 						mAudioHighPassFilter.get( sample ) * 
-						mSineWaveGenerator.getFloat() ) );
+						mSineWaveGenerator.inphase() ) );
 				
 				mSineWaveGenerator.rotate();
 				break;

src/main/java/io/github/dsheirer/audio/invert/AudioInverter.java

@@ -20,6 +20,7 @@ package io.github.dsheirer.audio.invert;
 import io.github.dsheirer.audio.InversionFrequency;
 import io.github.dsheirer.dsp.filter.Filters;
 import io.github.dsheirer.dsp.filter.FloatFIRFilter;
+import io.github.dsheirer.dsp.mixer.IOscillator;
 import io.github.dsheirer.dsp.mixer.Oscillator;
 import io.github.dsheirer.sample.real.RealSampleListener;
 
@@ -29,7 +30,7 @@ import io.github.dsheirer.sample.real.RealSampleListener;
  */
 public class AudioInverter implements RealSampleListener
 {
-	private Oscillator mSineWaveGenerator;
+	private IOscillator mSineWaveGenerator;
 	private FloatFIRFilter mPostInversionLowPassFilter;
 	private RealSampleListener mListener;
 	
@@ -61,7 +62,7 @@ public class AudioInverter implements RealSampleListener
 		if( mPostInversionLowPassFilter != null )
 		{
 			mPostInversionLowPassFilter.receive( 
-					sample * mSineWaveGenerator.getFloat() );
+					sample * mSineWaveGenerator.inphase() );
 			
 			mSineWaveGenerator.rotate();
 		}

src/main/java/io/github/dsheirer/audio/output/AudioOutput.java

@@ -19,10 +19,10 @@
 package io.github.dsheirer.audio.output;
 
 import io.github.dsheirer.audio.AudioEvent;
-import io.github.dsheirer.audio.AudioPacket;
 import io.github.dsheirer.channel.metadata.Metadata;
 import io.github.dsheirer.sample.Broadcaster;
 import io.github.dsheirer.sample.Listener;
+import io.github.dsheirer.sample.buffer.ReusableAudioPacket;
 import io.github.dsheirer.source.mixer.MixerChannel;
 import io.github.dsheirer.util.ThreadPool;
 import org.slf4j.Logger;
@@ -46,11 +46,11 @@ import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 
-public abstract class AudioOutput implements Listener<AudioPacket>, LineListener
+public abstract class AudioOutput implements Listener<ReusableAudioPacket>, LineListener
 {
     private final static Logger mLog = LoggerFactory.getLogger(AudioOutput.class);
 
-    private LinkedTransferQueue<AudioPacket> mBuffer = new LinkedTransferQueue<>();
+    private LinkedTransferQueue<ReusableAudioPacket> mBuffer = new LinkedTransferQueue<>();
     private int mBufferStartThreshold;
     private int mBufferStopThreshold;
 
@@ -190,7 +190,7 @@ public abstract class AudioOutput implements Listener<AudioPacket>, LineListener
      * Converts the audio packet data into a byte buffer format appropriate for
      * the underlying source data line.
      */
-    protected abstract ByteBuffer convert(AudioPacket packet);
+    protected abstract ByteBuffer convert(ReusableAudioPacket packet);
 
     /**
      * Audio output channel name
@@ -271,7 +271,7 @@ public abstract class AudioOutput implements Listener<AudioPacket>, LineListener
     }
 
     @Override
-    public void receive(AudioPacket packet)
+    public void receive(ReusableAudioPacket packet)
     {
         if(mCanProcessAudio)
         {
@@ -281,11 +281,17 @@ public abstract class AudioOutput implements Listener<AudioPacket>, LineListener
 
             mBuffer.add(packet);
         }
+        else
+        {
+            packet.decrementUserCount();
+        }
     }
 
     public class BufferProcessor implements Runnable
     {
         private AtomicBoolean mProcessing = new AtomicBoolean();
+        private List<ReusableAudioPacket> mAudioPackets = new ArrayList<ReusableAudioPacket>();
+
 
         public BufferProcessor()
         {
@@ -300,13 +306,11 @@ public abstract class AudioOutput implements Listener<AudioPacket>, LineListener
 				 * processor can run at any given time */
                 if(mProcessing.compareAndSet(false, true))
                 {
-                    List<AudioPacket> packets = new ArrayList<AudioPacket>();
+                    mBuffer.drainTo(mAudioPackets);
 
-                    mBuffer.drainTo(packets);
-
-                    for(AudioPacket packet : packets)
+                    for(ReusableAudioPacket packet : mAudioPackets)
                     {
-                        if(packet.getType() == AudioPacket.Type.AUDIO)
+                        if(packet.getType() == ReusableAudioPacket.Type.AUDIO)
                         {
                             broadcast(packet.getMetadata());
 
@@ -338,8 +342,14 @@ public abstract class AudioOutput implements Listener<AudioPacket>, LineListener
 
                             updateTimestamp();
                         }
+                        else
+                        {
+                            packet.decrementUserCount();
+                        }
                     }
 
+                    mAudioPackets.clear();
+
                     checkStop();
 
                     mProcessing.set(false);

src/main/java/io/github/dsheirer/audio/output/MonoAudioOutput.java

@@ -19,7 +19,7 @@
 package io.github.dsheirer.audio.output;
 
 import io.github.dsheirer.audio.AudioFormats;
-import io.github.dsheirer.audio.AudioPacket;
+import io.github.dsheirer.sample.buffer.ReusableAudioPacket;
 import io.github.dsheirer.source.mixer.MixerChannel;
 
 import javax.sound.sampled.Mixer;
@@ -43,14 +43,16 @@ public class MonoAudioOutput extends AudioOutput
     /**
      * Converts the audio packet data into mono audio frames.
      */
-    protected ByteBuffer convert(AudioPacket packet)
+    protected ByteBuffer convert(ReusableAudioPacket packet)
     {
-        if(packet.hasAudioBuffer())
+        ByteBuffer buffer = null;
+
+        if(packet.hasAudioSamples())
         {
-            float[] samples = packet.getAudioBuffer().getSamples();
+            float[] samples = packet.getAudioSamples();
 
 			/* Little-endian byte buffer */
-            ByteBuffer buffer = ByteBuffer.allocate(samples.length * 2).order(ByteOrder.LITTLE_ENDIAN);
+            buffer = ByteBuffer.allocate(samples.length * 2).order(ByteOrder.LITTLE_ENDIAN);
 
             ShortBuffer shortBuffer = buffer.asShortBuffer();
 
@@ -58,10 +60,10 @@ public class MonoAudioOutput extends AudioOutput
             {
                 shortBuffer.put((short) (sample * Short.MAX_VALUE));
             }
-
-            return buffer;
         }
 
-        return null;
+        packet.decrementUserCount();
+
+        return buffer;
     }
 }

src/main/java/io/github/dsheirer/audio/output/StereoAudioOutput.java

@@ -19,7 +19,7 @@
 package io.github.dsheirer.audio.output;
 
 import io.github.dsheirer.audio.AudioFormats;
-import io.github.dsheirer.audio.AudioPacket;
+import io.github.dsheirer.sample.buffer.ReusableAudioPacket;
 import io.github.dsheirer.source.mixer.MixerChannel;
 
 import javax.sound.sampled.Mixer;
@@ -45,15 +45,16 @@ public class StereoAudioOutput extends AudioOutput
      * channel containing the audio and the other channel containing zero
      * valued (silent) samples.
      */
-    protected ByteBuffer convert(AudioPacket packet)
+    protected ByteBuffer convert(ReusableAudioPacket packet)
     {
-        if(packet.hasAudioBuffer())
+        ByteBuffer buffer = null;
+
+        if(packet.hasAudioSamples())
         {
-            float[] samples = packet.getAudioBuffer().getSamples();
+            float[] samples = packet.getAudioSamples();
 
 			/* Little-endian byte buffer */
-            ByteBuffer buffer = ByteBuffer.allocate(samples.length * 4)
-                .order(ByteOrder.LITTLE_ENDIAN);
+            buffer = ByteBuffer.allocate(samples.length * 4).order(ByteOrder.LITTLE_ENDIAN);
 
             ShortBuffer shortBuffer = buffer.asShortBuffer();
 
@@ -73,10 +74,10 @@ public class StereoAudioOutput extends AudioOutput
                     shortBuffer.put((short) (sample * Short.MAX_VALUE));
                 }
             }
-
-            return buffer;
         }
 
-        return null;
+        packet.decrementUserCount();
+
+        return buffer;
     }
 }

src/main/java/io/github/dsheirer/audio/squelch/ManualSquelchController.java

@@ -1,40 +0,0 @@
-/*******************************************************************************
- *     SDR Trunk 
- *     Copyright (C) 2015 Dennis Sheirer
- * 
- *     This program is free software: you can redistribute it and/or modify
- *     it under the terms of the GNU General Public License as published by
- *     the Free Software Foundation, either version 3 of the License, or
- *     (at your option) any later version.
- * 
- *     This program is distributed in the hope that it will be useful,
- *     but WITHOUT ANY WARRANTY; without even the implied warranty of
- *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *     GNU General Public License for more details.
- * 
- *     You should have received a copy of the GNU General Public License
- *     along with this program.  If not, see <http://www.gnu.org/licenses/>
- ******************************************************************************/
-
-package io.github.dsheirer.audio.squelch;
-
-
-/**
- * Provides squelch control based on presense of decoded audio samples.
- * 
- * NOTE: this class is not yet fully implemented with audio sample processing
- * and currently only provides user driven squelch control
- */
-public class ManualSquelchController extends SquelchController
-{
-	public ManualSquelchController()
-	{
-		mSquelchMode = SquelchMode.NONE;
-	}
-
-	@Override
-	public void setSquelchMode( SquelchMode mode )
-	{
-		//TODO: add functionality
-	}
-}

src/main/java/io/github/dsheirer/audio/squelch/SquelchController.java

@@ -1,122 +0,0 @@
-/*******************************************************************************
- *     SDR Trunk 
- *     Copyright (C) 2015 Dennis Sheirer
- * 
- *     This program is free software: you can redistribute it and/or modify
- *     it under the terms of the GNU General Public License as published by
- *     the Free Software Foundation, either version 3 of the License, or
- *     (at your option) any later version.
- * 
- *     This program is distributed in the hope that it will be useful,
- *     but WITHOUT ANY WARRANTY; without even the implied warranty of
- *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *     GNU General Public License for more details.
- * 
- *     You should have received a copy of the GNU General Public License
- *     along with this program.  If not, see <http://www.gnu.org/licenses/>
- ******************************************************************************/
-
-package io.github.dsheirer.audio.squelch;
-
-import io.github.dsheirer.sample.Broadcaster;
-import io.github.dsheirer.sample.Listener;
-import io.github.dsheirer.sample.real.RealBuffer;
-import io.github.dsheirer.sample.real.RealSampleListener;
-import io.github.dsheirer.sample.real.RealToRealBufferAssembler;
-
-/**
- * Squelch control - receives single audio samples or real audio buffers and
- * adjusts squelch state either based on the audio samples or based on external
- * control inputs.  
- * 
- * Assembles received single audio samples into real sample buffers for
- * consumption by an external audio processor, like the AudioPacketProcessor
- * class.
- */
-public abstract class SquelchController 
-				implements Listener<RealBuffer>, RealSampleListener
-{
-	private Broadcaster<SquelchState> mSquelchStateBroadcaster = new Broadcaster<>();
-	private Listener<RealBuffer> mAudioListener;
-	protected SquelchState mSquelchState = SquelchState.UNSQUELCH;
-	protected SquelchMode mSquelchMode = SquelchMode.MANUAL;
-	
-	private RealToRealBufferAssembler mSampleAssembler = new RealToRealBufferAssembler( 512 );
-	
-	public SquelchController()
-	{
-		mSampleAssembler.setListener( this );
-	}
-	
-	@Override
-	public void receive( float sample )
-	{
-		mSampleAssembler.receive( sample );
-	}
-
-	@Override
-	public void receive( RealBuffer buffer )
-	{
-		if( mAudioListener != null )
-		{
-			mAudioListener.receive( buffer );
-		}
-	}
-
-	public abstract void setSquelchMode( SquelchMode mode );
-
-	public SquelchMode getSquelchMode()
-	{
-		return mSquelchMode;
-	}
-
-	public void setSquelchState( SquelchState state )
-	{
-		mSquelchState = state;
-	}
-
-	public SquelchState getSquelchState()
-	{
-		return mSquelchState;
-	}
-
-	public boolean isSquelched()
-	{
-		switch( mSquelchMode )
-		{
-			case AUTOMATIC:
-			case MANUAL:
-				return mSquelchState == SquelchState.SQUELCH;
-			case NONE:
-				return false;
-			default:
-				return false;
-		}
-	}
-	
-	public void addSquelchStateListener( Listener<SquelchState> listener )
-	{
-		if( listener != null )
-		{
-			mSquelchStateBroadcaster.addListener( listener );
-			
-			/* Send current squelch state to the listener */
-			listener.receive( mSquelchState );
-		}
-	}
-
-	public void removeSquelchStateListener( Listener<SquelchState> listener )
-	{
-		mSquelchStateBroadcaster.removeListener( listener );
-	}
-	
-	public void setAudioListener( Listener<RealBuffer> listener )
-	{
-		mAudioListener = listener;
-	}
-	
-	public void removeAudioListener( Listener<RealBuffer> listener )
-	{
-		mAudioListener = null;
-	}
-}

src/main/java/io/github/dsheirer/audio/squelch/TrunkingSquelchController.java

@@ -1,55 +0,0 @@
-/*******************************************************************************
- *     SDR Trunk 
- *     Copyright (C) 2015 Dennis Sheirer
- * 
- *     This program is free software: you can redistribute it and/or modify
- *     it under the terms of the GNU General Public License as published by
- *     the Free Software Foundation, either version 3 of the License, or
- *     (at your option) any later version.
- * 
- *     This program is distributed in the hope that it will be useful,
- *     but WITHOUT ANY WARRANTY; without even the implied warranty of
- *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *     GNU General Public License for more details.
- * 
- *     You should have received a copy of the GNU General Public License
- *     along with this program.  If not, see <http://www.gnu.org/licenses/>
- ******************************************************************************/
-
-package io.github.dsheirer.audio.squelch;
-
-public class TrunkingSquelchController extends SquelchController
-{
-	private boolean mAllowSquelchOverride = true;
-	
-	public TrunkingSquelchController()
-	{
-	}
-	
-	/**
-	 * Provides control over audio stream as directed by an external trunking
-	 * channel state.
-	 * 
-	 * Override automatic squelch control by setting the squelch mode to none.
-	 * 
-	 * Disable automatic control override by setting allowManualOverride to false;
-	 * 
-	 * Note: this control does not respond to squelch mode manual.
-	 */
-	public TrunkingSquelchController( boolean allowSquelchOverride )
-	{
-		mAllowSquelchOverride = allowSquelchOverride;
-		
-		mSquelchMode = SquelchMode.AUTOMATIC;
-	}
-
-	@Override
-	public void setSquelchMode( SquelchMode mode )
-	{
-		if( mode == SquelchMode.AUTOMATIC ||
-			( mode == SquelchMode.NONE && mAllowSquelchOverride ) )
-		{
-			mSquelchMode = mode;
-		}
-	}
-}

src/main/java/io/github/dsheirer/bits/IBinarySymbolProcessor.java

@@ -0,0 +1,21 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.bits;
+
+public interface IBinarySymbolProcessor
+{
+    void receive(boolean symbol);
+}

src/main/java/io/github/dsheirer/bits/ISyncDetectListener.java

@@ -1,6 +0,0 @@
-package io.github.dsheirer.bits;
-
-public interface ISyncDetectListener
-{
-	public void syncDetected();
-}

src/main/java/io/github/dsheirer/bits/ISyncProcessor.java

@@ -1,6 +1,26 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
 package io.github.dsheirer.bits;
 
 public interface ISyncProcessor
 {
-	public void checkSync( long value );
+    /**
+     * Checks if the value matches a known sync pattern
+     * @param value
+     * @return
+     */
+    boolean checkSync(long value);
 }

src/main/java/io/github/dsheirer/bits/MessageFramer.java

@@ -1,119 +1,116 @@
 /*******************************************************************************
- *     SDR Trunk 
- *     Copyright (C) 2014 Dennis Sheirer
- * 
- *     This program is free software: you can redistribute it and/or modify
- *     it under the terms of the GNU General Public License as published by
- *     the Free Software Foundation, either version 3 of the License, or
- *     (at your option) any later version.
- * 
- *     This program is distributed in the hope that it will be useful,
- *     but WITHOUT ANY WARRANTY; without even the implied warranty of
- *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *     GNU General Public License for more details.
- * 
- *     You should have received a copy of the GNU General Public License
- *     along with this program.  If not, see <http://www.gnu.org/licenses/>
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
  ******************************************************************************/
 package io.github.dsheirer.bits;
 
-import io.github.dsheirer.dsp.symbol.SyncDetectListener;
+import io.github.dsheirer.dsp.symbol.ISyncDetectListener;
 import io.github.dsheirer.dsp.symbol.SyncDetectProvider;
 import io.github.dsheirer.sample.Broadcaster;
 import io.github.dsheirer.sample.Listener;
 
 import java.util.ArrayList;
 import java.util.Iterator;
+import java.util.List;
 
 /**
  * MessageFramer - processes bitsets looking for a sync pattern within
  * the bits, and then extracts the message, including the sync
  * pattern, for a total bit length of messageLength.
- * 
+ *
  * Will extract multiple messages simultaneously, for each sync pattern that is
  * encountered within the bitset bit stream.
  */
-public class MessageFramer implements Listener<Boolean>, 
-									  SyncDetectProvider
+public class MessageFramer implements IBinarySymbolProcessor, Listener<Boolean>, SyncDetectProvider
 {
-	private boolean[] mSyncPattern;
-	private int mMessageLength;
-	private SyncDetectListener mSyncDetectListener;
-	private Broadcaster<BinaryMessage> mBroadcaster = 
-								new Broadcaster<BinaryMessage>();
-	private ArrayList<MessageAssembler> mMessageAssemblers = 
-                            new ArrayList<MessageAssembler>();
+    private boolean[] mSyncPattern;
+    private int mMessageLength;
+    private ISyncDetectListener mSyncDetectListener;
+    private Broadcaster<BinaryMessage> mBroadcaster = new Broadcaster<BinaryMessage>();
+    private List<MessageAssembler> mMessageAssemblers = new ArrayList<MessageAssembler>();
+    private List<MessageAssembler> mCompletedMessageAssemblers = new ArrayList<MessageAssembler>();
+    private SyncPatternMatcher mMatcher;
 
-	private ArrayList<MessageAssembler> mCompletedMessageAssemblers = 
-    								new ArrayList<MessageAssembler>();
-    
-	private BinaryMessage mPreviousBuffer = null;
-
-	private SyncPatternMatcher mMatcher;
-    
-    public MessageFramer( boolean[] syncPattern, int messageLength )
+    public MessageFramer(boolean[] syncPattern, int messageLength)
     {
         mSyncPattern = syncPattern;
-        mMatcher = new SyncPatternMatcher( syncPattern );
+        mMatcher = new SyncPatternMatcher(syncPattern);
         mMessageLength = messageLength;
     }
-    
+
     public void reset()
     {
-    	for( MessageAssembler assembler: mMessageAssemblers )
-    	{
-    		assembler.dispose();
-    	}
-        	
+        for(MessageAssembler assembler : mMessageAssemblers)
+        {
+            assembler.dispose();
+        }
+
         mMessageAssemblers.clear();
-    }    
-    
-    public void dispose()
-    {
-    	mBroadcaster.dispose();
-    	mCompletedMessageAssemblers.clear();
-    	mMessageAssemblers.clear();
     }
 
-    @Override
-    public void receive( Boolean bit )
+    public void dispose()
     {
-    	mMatcher.receive( bit );
-    	
+        mBroadcaster.dispose();
+        mCompletedMessageAssemblers.clear();
+        mMessageAssemblers.clear();
+    }
+
+    public void receive(boolean bit)
+    {
+        mMatcher.receive(bit);
+
         Iterator<MessageAssembler> it = mMessageAssemblers.iterator();
-        
+
         MessageAssembler assembler;
-        
-        while( it.hasNext() )
+
+        while(it.hasNext())
         {
             assembler = it.next();
 
             /* Dispose and remove any completed assemblers */
-            if( assembler.complete() )
+            if(assembler.complete())
             {
-            	assembler.dispose();
-            	it.remove();
+                assembler.dispose();
+                it.remove();
             }
             /* Otherwise, send them the bit */
             else
             {
-                assembler.receive( bit );
+                assembler.receive(bit);
             }
         }
-        
+
         /* Check for sync match and add new message assembler */
-    	if( mMatcher.matches() )
-    	{
-            addMessageAssembler( new MessageAssembler( mMessageLength, mSyncPattern ) );
-            
+        if(mMatcher.matches())
+        {
+            addMessageAssembler(new MessageAssembler(mMessageLength, mSyncPattern));
+
             /* Notify any sync detect listener(s) */
-            if( mSyncDetectListener != null )
+            if(mSyncDetectListener != null)
             {
-            	mSyncDetectListener.syncDetected();
+                mSyncDetectListener.syncDetected();
             }
-    	}
+        }
     }
-    
+
+    @Deprecated //Legacy support ... remove once all producers are converted to use receive(boolean bit) method
+    @Override
+    public void receive(Boolean bit)
+    {
+        receive(bit);
+    }
+
     /**
      * Causes all messages currently under assembly to be forcibly
      * sent (ie flushed) to all registered message listeners, and
@@ -121,44 +118,44 @@ public class MessageFramer implements Listener<Boolean>,
      */
     public void flush()
     {
-        for( MessageAssembler assembler: mMessageAssemblers )
+        for(MessageAssembler assembler : mMessageAssemblers)
         {
             assembler.flush();
         }
     }
-    
-	@Override
-    public void setSyncDetectListener( SyncDetectListener listener )
+
+    @Override
+    public void setSyncDetectListener(ISyncDetectListener listener)
     {
-		mSyncDetectListener = listener;
+        mSyncDetectListener = listener;
     }
-    
+
     /**
      * Allow a message listener to register with this framer to receive
      * all framed messages
      */
-    public void addMessageListener( Listener<BinaryMessage> listener )
+    public void addMessageListener(Listener<BinaryMessage> listener)
     {
-        mBroadcaster.addListener( listener );
+        mBroadcaster.addListener(listener);
     }
-    
-    public void removeMessageListener( Listener<BinaryMessage> listener )
+
+    public void removeMessageListener(Listener<BinaryMessage> listener)
     {
-        mBroadcaster.removeListener( listener );
+        mBroadcaster.removeListener(listener);
     }
 
     /*
      * Adds a message assembler to receive bits from the bit stream
      */
-    private void addMessageAssembler( MessageAssembler assembler )
+    private void addMessageAssembler(MessageAssembler assembler)
     {
-        mMessageAssemblers.add( assembler );
+        mMessageAssemblers.add(assembler);
     }
 
-    @SuppressWarnings( "unused" )
-	private void removeMessageAssembler( MessageAssembler assembler )
+    @SuppressWarnings("unused")
+    private void removeMessageAssembler(MessageAssembler assembler)
     {
-        mMessageAssemblers.remove( assembler );
+        mMessageAssemblers.remove(assembler);
     }
 
     /**
@@ -166,7 +163,7 @@ public class MessageFramer implements Listener<Boolean>,
      * identified sync pattern, and every bit thereafter.  Once the accumulated
      * bits equal the message length, the message is sent and the assembler
      * flags itself as complete.
-     * 
+     *
      * By design, multiple message assemblers can exist at the same time, each
      * assembling different, overlapping potential messages
      */
@@ -174,46 +171,46 @@ public class MessageFramer implements Listener<Boolean>,
     {
         BinaryMessage mMessage;
         boolean mComplete = false;
-        
-        MessageAssembler( int messageLength )
+
+        MessageAssembler(int messageLength)
         {
-            mMessage = new BinaryMessage( messageLength );
+            mMessage = new BinaryMessage(messageLength);
         }
-        
-        MessageAssembler( int messageLength, boolean[] initialFill )
+
+        MessageAssembler(int messageLength, boolean[] initialFill)
         {
-            this(  messageLength );
-            
+            this(messageLength);
+
             /* Pre-load the message with the sync pattern */
-            for( int x = 0; x < initialFill.length; x++ )
+            for(int x = 0; x < initialFill.length; x++)
             {
-                receive( initialFill[ x ] );
+                receive(initialFill[x]);
             }
         }
-        
+
         public void dispose()
         {
-        	mMessage = null;
+            mMessage = null;
         }
 
         @Override
         /**
          * Receives one bit at a time, and assembles them into a message
          */
-        public void receive( Boolean bit )
+        public void receive(Boolean bit)
         {
             try
             {
-                mMessage.add( bit );
+                mMessage.add(bit);
             }
-            catch( BitSetFullException e )
+            catch(BitSetFullException e)
             {
                 e.printStackTrace();
             }
-            
+
             /* Once our message is complete (ie full), send it to all registered
              * message listeners, and set complete flag so for auto-removal */
-            if( mMessage.isFull() )
+            if(mMessage.isFull())
             {
                 mComplete = true;
                 flush();
@@ -226,7 +223,7 @@ public class MessageFramer implements Listener<Boolean>,
          */
         public void flush()
         {
-            mBroadcaster.receive( mMessage );
+            mBroadcaster.receive(mMessage);
             mComplete = true;
         }
 

src/main/java/io/github/dsheirer/bits/MultiSyncPatternMatcher.java

@@ -1,111 +1,130 @@
 /*******************************************************************************
- *     SDR Trunk 
- *     Copyright (C) 2014 Dennis Sheirer
- * 
- *     This program is free software: you can redistribute it and/or modify
- *     it under the terms of the GNU General Public License as published by
- *     the Free Software Foundation, either version 3 of the License, or
- *     (at your option) any later version.
- * 
- *     This program is distributed in the hope that it will be useful,
- *     but WITHOUT ANY WARRANTY; without even the implied warranty of
- *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *     GNU General Public License for more details.
- * 
- *     You should have received a copy of the GNU General Public License
- *     along with this program.  If not, see <http://www.gnu.org/licenses/>
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
  ******************************************************************************/
 package io.github.dsheirer.bits;
 
+import io.github.dsheirer.dsp.symbol.ISyncDetectListener;
 import org.apache.commons.lang3.Validate;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.util.ArrayList;
 import java.util.List;
 
 /**
- * Multi-Sync pattern matcher.  Accepts multiple sync detector objects for 
+ * Multi-Sync pattern matcher.  Accepts multiple sync detector objects for
  * comparision against the incoming bit stream.
- * 
+ *
  * Note: works for sync patterns up to 63 bits (integer size - 1 ) long.
  * If a 64 bit or larger sync pattern is applied, then the wrapping feature
  * of the Long.rotate methods will wrap the MSB around to the LSB and
  * corrupt the matching value.
- *
  */
 public class MultiSyncPatternMatcher
 {
-	private List<ISyncProcessor> mSyncProcessors = new ArrayList<ISyncProcessor>();
-	
-	private long mBits = 0;
-	private long mMask = 0;
-	
-	public MultiSyncPatternMatcher( int syncSize )
-	{
-		Validate.isTrue(syncSize < 64);
-		
-		//Setup a bit mask of all ones the length of the sync pattern
-		mMask = (long)( ( Math.pow( 2, syncSize ) ) - 1 );
-	}
-	
-	public void dispose()
-	{
-		mSyncProcessors.clear();
-	}
-	
-	/**
-	 * Processes two bits before checking sync processors for a match.
-	 */
-	public void receive( boolean bit1, boolean bit2 )
-	{
-		mBits = Long.rotateLeft( mBits, 1 );
-		
-		mBits &= mMask;
-		
-		if( bit1 )
-		{
-			mBits += 1;
-		}
+    private final static Logger mLog = LoggerFactory.getLogger(MultiSyncPatternMatcher.class);
 
-		mBits = Long.rotateLeft( mBits, 1 );
-		
-		mBits &= mMask;
-		
-		if( bit2 )
-		{
-			mBits += 1;
-		}
+    private ISyncDetectListener mSyncDetectListener;
+    private int mSyncLossThreshold;
+    private int mBitCount;
+    private List<ISyncProcessor> mSyncProcessors = new ArrayList<ISyncProcessor>();
 
-		for( ISyncProcessor processor: mSyncProcessors )
-		{
-			processor.checkSync( mBits );
-		}
-	}
-	
-	/**
-	 * Processes one bit before checking sync processors for a match.
-	 */
-	public void receive( boolean bit )
-	{
-		mBits = Long.rotateLeft( mBits, 1 );
-		
-		mBits &= mMask;
-		
-		if( bit )
-		{
-			mBits += 1;
-		}
+    private long mBits = 0;
+    private long mMask = 0;
 
-		for( ISyncProcessor processor: mSyncProcessors )
-		{
-			processor.checkSync( mBits );
-		}
-	}
+    public MultiSyncPatternMatcher(ISyncDetectListener syncDetectListener, int syncLossThreshold, int syncSize)
+    {
+        mSyncDetectListener = syncDetectListener;
+        mSyncLossThreshold = syncLossThreshold;
+        Validate.isTrue(syncSize < 64);
 
-	/**
-	 * Adds a sync processor to receive the bit stream.
-	 */
-	public void add( ISyncProcessor processor )
-	{
-		mSyncProcessors.add( processor );
-	}
+        //Setup a bit mask of all ones the length of the sync pattern
+        mMask = (long)((Math.pow(2, syncSize)) - 1);
+    }
+
+    public void dispose()
+    {
+        mSyncProcessors.clear();
+    }
+
+    /**
+     * Processes two bits before checking sync processors for a match.
+     */
+    public void receive(boolean bit1, boolean bit2)
+    {
+        mBits = Long.rotateLeft(mBits, 1);
+
+        mBits &= mMask;
+
+        if(bit1)
+        {
+            mBits += 1;
+        }
+
+        mBits = Long.rotateLeft(mBits, 1);
+
+        mBits &= mMask;
+
+        if(bit2)
+        {
+            mBits += 1;
+        }
+
+        mBitCount += 2;
+
+        for(ISyncProcessor processor : mSyncProcessors)
+        {
+            if(processor.checkSync(mBits))
+            {
+                mSyncDetectListener.syncDetected();
+                mBitCount = 0;
+            }
+        }
+
+        if(mBitCount > mSyncLossThreshold)
+        {
+            mBitCount = 0;
+            mSyncDetectListener.syncLost();
+        }
+    }
+
+    /**
+     * Processes one bit before checking sync processors for a match.
+     */
+    public void receive(boolean bit)
+    {
+        mBits = Long.rotateLeft(mBits, 1);
+
+        mBits &= mMask;
+
+        if(bit)
+        {
+            mBits += 1;
+        }
+
+        for(ISyncProcessor processor : mSyncProcessors)
+        {
+            processor.checkSync(mBits);
+        }
+    }
+
+    /**
+     * Adds a sync processor to receive the bit stream.
+     */
+    public void add(ISyncProcessor processor)
+    {
+        mSyncProcessors.add(processor);
+    }
 }

src/main/java/io/github/dsheirer/bits/SoftSyncDetector.java

@@ -1,48 +1,68 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
 package io.github.dsheirer.bits;
 
+import io.github.dsheirer.dsp.symbol.ISyncDetectListener;
+
 public class SoftSyncDetector implements ISyncProcessor
 {
-	private ISyncDetectListener mListener;
-	private long mPattern;
-	private int mThreshold;
-	
-	public SoftSyncDetector( ISyncDetectListener listener, long pattern, int threshold )
-	{
-		this( pattern, threshold );
-		
-		mListener = listener;
-	}
-	
-	public SoftSyncDetector( long pattern, int threshold )
-	{
-		mPattern = pattern;
-		mThreshold = threshold;
-	}
-	
-	public void dispose()
-	{
-		mListener = null;
-	}
+    private ISyncDetectListener mListener;
+    private long mPattern;
+    private int mThreshold;
 
-	@Override
-	public void checkSync( long value )
-	{
-		long difference = value ^ mPattern;
-		
-		if( ( difference == 0 || Long.bitCount( difference ) <= mThreshold ) &&
-			  mListener != null )
-		{
-			mListener.syncDetected();
-		}
-	}
-	
-	public void setThreshold( int threshold )
-	{
-		mThreshold = threshold;
-	}
-	
-	public void setListener( ISyncDetectListener listener )
-	{
-		mListener = listener;
-	}
+    public SoftSyncDetector(ISyncDetectListener listener, long pattern, int threshold)
+    {
+        this(pattern, threshold);
+
+        mListener = listener;
+    }
+
+    public SoftSyncDetector(long pattern, int threshold)
+    {
+        mPattern = pattern;
+        mThreshold = threshold;
+    }
+
+    public void dispose()
+    {
+        mListener = null;
+    }
+
+    @Override
+    public boolean checkSync(long value)
+    {
+        long difference = value ^ mPattern;
+
+        if((difference == 0 || Long.bitCount(difference) <= mThreshold) &&
+            mListener != null)
+        {
+            mListener.syncDetected();
+            return true;
+        }
+
+        return false;
+    }
+
+    public void setThreshold(int threshold)
+    {
+        mThreshold = threshold;
+    }
+
+    public void setListener(ISyncDetectListener listener)
+    {
+        mListener = listener;
+    }
 }

src/main/java/io/github/dsheirer/bits/SyncDetector.java

@@ -1,33 +1,57 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
 package io.github.dsheirer.bits;
 
+import io.github.dsheirer.dsp.symbol.ISyncDetectListener;
+
 public class SyncDetector implements ISyncProcessor
 {
-	private long mPattern;
-	private ISyncDetectListener mListener;
+    private long mPattern;
+    private ISyncDetectListener mListener;
 
-	public SyncDetector( long pattern )
-	{
-		mPattern = pattern;
-	}
-	
-	public SyncDetector( long pattern, ISyncDetectListener listener )
-	{
-		this( pattern );
-		
-		mListener = listener;
-	}
-	
-	public void setListener( ISyncDetectListener listener )
-	{
-		mListener = listener;
-	}
+    public SyncDetector(long pattern)
+    {
+        mPattern = pattern;
+    }
 
-	@Override
-	public void checkSync( long value )
-	{
-		if( value == mPattern && mListener != null )
-		{
-			mListener.syncDetected();
-		}
-	}
+    public SyncDetector(long pattern, ISyncDetectListener listener)
+    {
+        this(pattern);
+
+        mListener = listener;
+    }
+
+    public void setListener(ISyncDetectListener listener)
+    {
+        mListener = listener;
+    }
+
+    @Override
+    public boolean checkSync(long value)
+    {
+        if(value == mPattern)
+        {
+            if(mListener != null)
+            {
+                mListener.syncDetected();
+            }
+
+            return true;
+        }
+
+        return false;
+    }
 }

src/main/java/io/github/dsheirer/bits/SyncPattern.java

@@ -29,7 +29,7 @@ public enum SyncPattern
 		false, false, false, false           //0000 0x0
 	} ),
 
-	/* Revs (0x0A) and Sync (0x23EB) = 10101 0010001111101011 */
+	/* Revs (0x0A) and Sync (0x23EB) = 0101 000 1 000 11111 0 1 0 11 */
 	FLEETSYNC2( new boolean[] 
 	{ 
 		false, true, false, true, false,	//End of bit revs

src/main/java/io/github/dsheirer/bits/SyncPatternMatcher.java

@@ -1,17 +1,17 @@
 /*******************************************************************************
  *     SDR Trunk 
  *     Copyright (C) 2014 Dennis Sheirer
- * 
+ *
  *     This program is free software: you can redistribute it and/or modify
  *     it under the terms of the GNU General Public License as published by
  *     the Free Software Foundation, either version 3 of the License, or
  *     (at your option) any later version.
- * 
+ *
  *     This program is distributed in the hope that it will be useful,
  *     but WITHOUT ANY WARRANTY; without even the implied warranty of
  *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  *     GNU General Public License for more details.
- * 
+ *
  *     You should have received a copy of the GNU General Public License
  *     along with this program.  If not, see <http://www.gnu.org/licenses/>
  ******************************************************************************/
@@ -20,113 +20,112 @@ package io.github.dsheirer.bits;
 
 /**
  * Sync pattern matcher.
- * 
+ *
  * Note: works for sync patterns up to 63 bits (integer size - 1 ) long.
  * If a 64 bit or larger sync pattern is applied, then the wrapping feature
  * of the Long.rotate methods will wrap the MSB around to the LSB and
  * corrupt the matching value.
- *
  */
 public class SyncPatternMatcher
 {
-	private long mBits = 0;
-	private long mMask = 0;
-	private long mSync = 0;
-	private boolean mSoftMode = false;
-	private int mSoftModeErrorThreshold = 0;
-	
-	public SyncPatternMatcher( boolean[] syncPattern )
-	{
-		//Setup a bit mask of all ones the length of the sync pattern
-		mMask = (long)( ( Math.pow( 2, syncPattern.length ) ) - 1 );
-		
-		//Convert the sync bits into a long value for comparison
-		for( int x = 0; x < syncPattern.length; x++ )
-		{
-			if( syncPattern[ x ] )
-			{
-    			mSync += 1l << ( syncPattern.length - 1 - x );
-			}
-		}
-	}
-	
-	public SyncPatternMatcher( long sync )
-	{
-		mSync = sync;
-		mMask = getMask( sync );
-	}
+    private long mBits = 0;
+    private long mMask = 0;
+    private long mSync = 0;
+    private boolean mSoftMode = false;
+    private int mSoftModeErrorThreshold = 0;
 
-	/**
-	 * Constructs the sync pattern matcher and defines the soft mode maximum
-	 * number of bit errors to allow in the pattern match.
-	 * 
-	 * @param sync pattern
-	 * @param softModeErrorThreshold - maximum bit errors (ie pattern mismatch
-	 * positions) when considering a sync match
-	 */
-	public SyncPatternMatcher( long sync, int softModeErrorThreshold )
-	{
-		this( sync );
-		
-		mSoftModeErrorThreshold = softModeErrorThreshold;
-	}
+    public SyncPatternMatcher(boolean[] syncPattern)
+    {
+        //Setup a bit mask of all ones the length of the sync pattern
+        mMask = (long)((Math.pow(2, syncPattern.length)) - 1);
 
-	/**
-	 * Generates an all ones mask corresponding to the sync pattern
-	 */
-	private static long getMask( long sync )
-	{
-		long mask = sync;
-		
-		for( int x = 1; x < 64; x *= 2 )
-		{
-			mask |= ( mask >> x );
-		}
-		
-		return mask;
-	}
-	
-	
-	public void receive( boolean bit )
-	{
-		//Left shift the previous value
-		mBits = Long.rotateLeft( mBits, 1 );
-		
-		//Apply the mask to erase the previous MSB
-		mBits &= mMask;
-		
-		//Add in the new bit
-		if( bit )
-		{
-			mBits += 1;
-		}
-	}
+        //Convert the sync bits into a long value for comparison
+        for(int x = 0; x < syncPattern.length; x++)
+        {
+            if(syncPattern[x])
+            {
+                mSync += 1l << (syncPattern.length - 1 - x);
+            }
+        }
+    }
 
-	/**
-	 * Indicates if the most recently received bit sequence matches the 
-	 * sync pattern
-	 */
-	public boolean matches()
-	{
-		if( mSoftMode )
-		{
-			long difference = mBits ^ mSync;
-			
-			return difference == 0 || 
-					Long.bitCount( difference ) <= mSoftModeErrorThreshold;
-		}
-		else
-		{
-			return ( mBits == mSync );
-		}
-	}
+    public SyncPatternMatcher(long sync)
+    {
+        mSync = sync;
+        mMask = getMask(sync);
+    }
 
-	/**
-	 * Sets the sync pattern matcher in soft mode which allows up to the soft
-	 * mode threshold number of bit errors when considering a sync pattern match
-	 */
-	public void setSoftMode( boolean softMode )
-	{
-		mSoftMode = softMode;
-	}
+    /**
+     * Constructs the sync pattern matcher and defines the soft mode maximum
+     * number of bit errors to allow in the pattern match.
+     *
+     * @param sync pattern
+     * @param softModeErrorThreshold - maximum bit errors (ie pattern mismatch
+     * positions) when considering a sync match
+     */
+    public SyncPatternMatcher(long sync, int softModeErrorThreshold)
+    {
+        this(sync);
+
+        mSoftModeErrorThreshold = softModeErrorThreshold;
+    }
+
+    /**
+     * Generates an all ones mask corresponding to the sync pattern
+     */
+    private static long getMask(long sync)
+    {
+        long mask = sync;
+
+        for(int x = 1; x < 64; x *= 2)
+        {
+            mask |= (mask >> x);
+        }
+
+        return mask;
+    }
+
+
+    public void receive(boolean bit)
+    {
+        //Left shift the previous value
+        mBits = Long.rotateLeft(mBits, 1);
+
+        //Apply the mask to erase the previous MSB
+        mBits &= mMask;
+
+        //Add in the new bit
+        if(bit)
+        {
+            mBits += 1;
+        }
+    }
+
+    /**
+     * Indicates if the most recently received bit sequence matches the
+     * sync pattern
+     */
+    public boolean matches()
+    {
+        if(mSoftMode)
+        {
+            long difference = mBits ^ mSync;
+
+            return difference == 0 ||
+                Long.bitCount(difference) <= mSoftModeErrorThreshold;
+        }
+        else
+        {
+            return (mBits == mSync);
+        }
+    }
+
+    /**
+     * Sets the sync pattern matcher in soft mode which allows up to the soft
+     * mode threshold number of bit errors when considering a sync pattern match
+     */
+    public void setSoftMode(boolean softMode)
+    {
+        mSoftMode = softMode;
+    }
 }

src/main/java/io/github/dsheirer/buffer/BooleanAveragingBuffer.java

@@ -1,107 +1,89 @@
 /*******************************************************************************
  *     SDR Trunk 
  *     Copyright (C) 2014 Dennis Sheirer
- * 
+ *
  *     This program is free software: you can redistribute it and/or modify
  *     it under the terms of the GNU General Public License as published by
  *     the Free Software Foundation, either version 3 of the License, or
  *     (at your option) any later version.
- * 
+ *
  *     This program is distributed in the hope that it will be useful,
  *     but WITHOUT ANY WARRANTY; without even the implied warranty of
  *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  *     GNU General Public License for more details.
- * 
+ *
  *     You should have received a copy of the GNU General Public License
  *     along with this program.  If not, see <http://www.gnu.org/licenses/>
  ******************************************************************************/
 package io.github.dsheirer.buffer;
 
-import java.util.Arrays;
-
-
 /**
  * Circular Buffer - implements a circular buffer with a method to get the
  * current head of the buffer, and put a new value in its place at the same
  * time
- * 
+ *
  * Also provides averaging over the elements in the buffer
  */
-public class BooleanAveragingBuffer {
+public class BooleanAveragingBuffer
+{
+    private boolean[] mBuffer;
+    private int mBufferPointer;
+    private int mThreshold;
+    private int mTrueCount;
 
-	private boolean[] mBuffer;
-	private int mBufferPointer;
-	
-	public BooleanAveragingBuffer( int length )
-	{
-		mBuffer = new boolean[ length ];
-		
-		//Preload the array with false values
-		Arrays.fill( mBuffer, false );
-	}
-	
-	public boolean get( boolean newValue )
-	{
-		//Fetch current boolean value
-		boolean retVal = mBuffer[ mBufferPointer ];
+    public BooleanAveragingBuffer(int length)
+    {
+        mBuffer = new boolean[length];
+        mThreshold = length / 2;
+    }
 
-		//Load the new value into the buffer
-		put( newValue );
-		
-		return retVal;
-	}
+    public boolean get(boolean newValue)
+    {
+        //Fetch current boolean value
+        boolean retVal = mBuffer[mBufferPointer];
 
-	/**
-	 * Loads the newValue into this buffer and adjusts the buffer pointer
-	 * to prepare for the next get/put cycle
-	 */
-	private void put( boolean newValue )
-	{
-		//Store the new value to the buffer
-		mBuffer[ mBufferPointer ] = newValue;
-		
-		//Increment the buffer pointer
-		mBufferPointer++;
+        //Load the new value into the buffer
+        put(newValue);
 
-		//Wrap the buffer pointer around to 0 when necessary
-		if( mBufferPointer >= mBuffer.length )
-		{
-			mBufferPointer = 0;
-		}
-	}
+        return retVal;
+    }
 
-	/**
-	 * Loads the newValue into the buffer, calculates the average
-	 * and returns that average from this method
-	 * 
-	 * This effectively performs low-pass filtering
-	 */
-	public boolean getAverage( boolean newValue )
-	{
-		//Load the new value into the buffer
-		put( newValue );
-		
-		int trueCount = 0;
-		
-		for( int x = 0; x < mBuffer.length; x++ )
-		{
-			if( mBuffer[ x ] )
-			{
-				trueCount++;
-			}
-		}
+    /**
+     * Loads the newValue into this buffer and adjusts the buffer pointer
+     * to prepare for the next get/put cycle
+     */
+    private void put(boolean newValue)
+    {
+        //Store the new value to the buffer
+        mBuffer[mBufferPointer] = newValue;
 
-		/**
-		 * If the number of true values in the buffer is
-		 * more than half, return true, otherwise, false
-		 */
-		if( trueCount > (int)( mBuffer.length / 2 ) )
-		{
-			return true;
-		}
-		else
-		{
-			return false;
-		}
-	}
+        //Increment the buffer pointer
+        mBufferPointer++;
+
+        mBufferPointer = mBufferPointer % mBuffer.length;
+    }
+
+    /**
+     * Loads the newValue into the buffer, calculates the average
+     * and returns that average from this method
+     *
+     * This effectively performs low-pass filtering
+     */
+    public boolean getAverage(boolean newValue)
+    {
+        //Load the new value into the buffer
+        put(newValue);
+
+        mTrueCount = 0;
+
+        for(int x = 0; x < mBuffer.length; x++)
+        {
+            if(mBuffer[x])
+            {
+                mTrueCount++;
+            }
+        }
+
+        return mTrueCount > mThreshold;
+    }
 }

src/main/java/io/github/dsheirer/buffer/CircularBuffer.java

@@ -1,3 +1,18 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
 package io.github.dsheirer.buffer;
 
 import io.github.dsheirer.sample.Listener;
@@ -8,87 +23,86 @@ import java.util.List;
 
 public class CircularBuffer<T> implements Listener<T>
 {
-	private ArrayList<T> mElements;
-	private Listener<T> mListener;
-	private int mPointer;
-	private int mSize;
+    private List<T> mElements;
+    private Listener<T> mListener;
+    private int mPointer;
+    private int mSize;
 
 
-	/**
-	 * Circular Buffer - stores elements in an array list.  Once the buffer is
-	 * full, new samples replace older samples and older samples are broadcast
-	 * to an optional listener.
-	 * 
-	 * @param size - size of buffer
-	 */
-	public CircularBuffer( int size )
-	{
-		mSize = size;
-		mElements = new ArrayList<T>();
-	}
+    /**
+     * Circular Buffer - stores elements in an array list.  Once the buffer is
+     * full, new samples replace older samples and older samples are broadcast
+     * to an optional listener.
+     *
+     * @param size - size of buffer
+     */
+    public CircularBuffer(int size)
+    {
+        mSize = size;
+        mElements = new ArrayList<T>();
+    }
 
-	/**
-	 * Returns the element stored at index.  Note: the index argument refers to
-	 * the internal storage index and does not indicate a temporal relationship
-	 * among elements.  For example, if you get indexes 1, 2, and 3, you may be
-	 * getting ( oldest - 1, oldest, newest ) elements, if the internal pointer
-	 * is currently pointing to and will insert the next element at index 4.
-	 * 
-	 * @param index - element index
-	 * 
-	 * @return element or null
-	 */
-	public T get( int index )
-	{
-		if( index < mElements.size() )
-		{
-			return mElements.get( index );
-		}
-		
-		return null;
-	}
-	
-	public int getSize()
-	{
-		return mSize;
-	}
-	
-	public List<T> getElements()
-	{
-		return Collections.unmodifiableList( mElements );
-	}
-	
-	@Override
-	public void receive( T element )
-	{
-		T previous = null;
-		
-		if( mElements.size() > mPointer )
-		{
-			previous = mElements.get( mPointer );
-			
-			mElements.set( mPointer, element );
-		}
-		else
-		{
-			mElements.add( element );
-		}
-		
-		mPointer++;
-		
-		if( mPointer >= mSize )
-		{
-			mPointer = 0;
-		}
-		
-		if( previous != null && mListener != null )
-		{
-			mListener.receive( previous );
-		}
-	}
+    /**
+     * Returns the element stored at index.  Note: the index argument refers to
+     * the internal storage index and does not indicate a temporal relationship
+     * among elements.  For example, if you get indexes 1, 2, and 3, you may be
+     * getting ( oldest - 1, oldest, newest ) elements, if the internal pointer
+     * is currently pointing to and will insert the next element at index 4.
+     *
+     * @param index - element index
+     * @return element or null
+     */
+    public T get(int index)
+    {
+        if(index < mElements.size())
+        {
+            return mElements.get(index);
+        }
 
-	public void setListener( Listener<T> listener )
-	{
-		mListener = listener;
-	}
+        return null;
+    }
+
+    public int getSize()
+    {
+        return mSize;
+    }
+
+    public List<T> getElements()
+    {
+        return Collections.unmodifiableList(mElements);
+    }
+
+    @Override
+    public void receive(T element)
+    {
+        T previous = null;
+
+        if(mElements.size() > mPointer)
+        {
+            previous = mElements.get(mPointer);
+
+            mElements.set(mPointer, element);
+        }
+        else
+        {
+            mElements.add(element);
+        }
+
+        mPointer++;
+
+        if(mPointer >= mSize)
+        {
+            mPointer = 0;
+        }
+
+        if(previous != null && mListener != null)
+        {
+            mListener.receive(previous);
+        }
+    }
+
+    public void setListener(Listener<T> listener)
+    {
+        mListener = listener;
+    }
 }

src/main/java/io/github/dsheirer/buffer/RealCircularBuffer.java

@@ -0,0 +1,124 @@
+/*******************************************************************************
+ * sdrtrunk
+ * Copyright (C) 2014-2017 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.buffer;
+
+/**
+ * Circular sample buffer - allocates a buffer and stores samples in a circular
+ * fashion, overwriting older samples with newly arrived samples.
+ *
+ * Can be used as a delay-type buffer, to delay samples by the 'size' amount
+ */
+public class RealCircularBuffer
+{
+    float[] mBuffer;
+    int mBufferPointer = 0;
+
+    public RealCircularBuffer(int size)
+    {
+        mBuffer = new float[size];
+    }
+
+    public int getSize()
+    {
+        return mBuffer.length;
+    }
+
+    public float[] getBuffer()
+    {
+        return mBuffer;
+    }
+
+    /**
+     * Puts the new value into the buffer and returns the oldest buffer value
+     * that it replaced
+     *
+     * @param newValue
+     * @return
+     */
+    public float putAndGet(float newValue)
+    {
+        float oldestSample = mBuffer[mBufferPointer];
+
+        put(newValue);
+
+        return oldestSample;
+    }
+
+    /**
+     * Adds the new value to this buffer.
+     */
+    public void put(float newValue)
+    {
+        mBuffer[mBufferPointer] = newValue;
+
+        mBufferPointer++;
+
+        if(mBufferPointer >= mBuffer.length)
+        {
+            mBufferPointer = 0;
+        }
+    }
+
+    /**
+     * Returns the sample at the specified index, where index 0 is the oldest sample and index (length - 1) is the
+     * newest sample.
+     * @param index in range of 0 to length-1
+     * @return value at indexed position
+     */
+
+    public float get(int index)
+    {
+        if(index < mBuffer.length)
+        {
+            int pointer = mBufferPointer + index;
+
+            if(pointer >= mBuffer.length)
+            {
+                pointer -= mBuffer.length;
+            }
+
+            return mBuffer[pointer];
+        }
+        else
+        {
+            throw new ArrayIndexOutOfBoundsException("Index [" + index + "] is not valid for the buffer size of [" +
+                mBuffer.length + "]");
+        }
+    }
+
+    /**
+     * Returns the contents of the circular buffer unwrapped where index 0 is the oldest sample and index length-1
+     * is the newest sample.
+     *
+     * @return array of samples
+     */
+    public float[] get()
+    {
+        float[] samples = new float[mBuffer.length];
+
+        System.arraycopy(mBuffer, mBufferPointer, samples, 0, mBuffer.length - mBufferPointer);
+
+        if(mBufferPointer != 0)
+        {
+            System.arraycopy(mBuffer, 0, samples, mBuffer.length - mBufferPointer, mBufferPointer);
+        }
+
+        return samples;
+    }
+}

src/main/java/io/github/dsheirer/channel/metadata/AttributeMonitor.java

@@ -123,6 +123,11 @@ public class AttributeMonitor<T>
     {
         mCurrentValue = null;
         mOccurrenceCounts.clear();
+
+        if(mListener != null)
+        {
+            mListener.receive(new AttributeChangeRequest(mAttribute, null, null));
+        }
     }
 
     /**

src/main/java/io/github/dsheirer/channel/metadata/ChannelMetadataPanel.java

@@ -25,32 +25,36 @@ import io.github.dsheirer.controller.channel.ChannelProcessingManager;
 import io.github.dsheirer.controller.channel.ChannelUtils;
 import io.github.dsheirer.icon.IconManager;
 import io.github.dsheirer.module.ProcessingChain;
-import io.github.dsheirer.properties.SystemProperties;
 import io.github.dsheirer.sample.Broadcaster;
 import io.github.dsheirer.sample.Listener;
 import net.miginfocom.swing.MigLayout;
 import org.apache.commons.lang3.Validate;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
-import javax.swing.*;
+import javax.swing.JLabel;
+import javax.swing.JMenuItem;
+import javax.swing.JPanel;
+import javax.swing.JPopupMenu;
+import javax.swing.JScrollPane;
+import javax.swing.JTable;
+import javax.swing.SwingConstants;
 import javax.swing.event.ListSelectionEvent;
 import javax.swing.event.ListSelectionListener;
 import javax.swing.table.DefaultTableCellRenderer;
-import java.awt.*;
+import java.awt.Color;
+import java.awt.Component;
 import java.awt.event.MouseAdapter;
 import java.awt.event.MouseEvent;
+import java.util.HashMap;
+import java.util.Map;
 
 public class ChannelMetadataPanel extends JPanel implements ListSelectionListener
 {
-    private final static Logger mLog = LoggerFactory.getLogger(ChannelMetadataPanel.class);
-
-    private static final String PROPERTY_PREFIX_BACKGROUND = "channel.metadata.panel.state.color.";
-    private static final String PROPERTY_PREFIX_FOREGROUND = "channel.metadata.panel.text.color.";
     private ChannelProcessingManager mChannelProcessingManager;
     private IconManager mIconManager;
     private JTable mTable;
     private Broadcaster<ProcessingChain> mSelectedProcessingChainBroadcaster = new Broadcaster<>();
+    private Map<State,Color> mBackgroundColors = new HashMap<>();
+    private Map<State,Color> mForegroundColors = new HashMap<>();
 
     /**
      * Table view for currently decoding channel metadata
@@ -94,7 +98,34 @@ public class ChannelMetadataPanel extends JPanel implements ListSelectionListene
 
         add(scrollPane);
 
-//        new TableColumnWidthMonitor(mTable, PROPERTY_PREFIX, new int[] {15,15,15,15,25,25,25,25,15,40});
+        setColors();
+    }
+
+    /**
+     * Setup the background and foreground color palette for the various channel states.
+     */
+    private void setColors()
+    {
+        mBackgroundColors.put(State.ACTIVE, Color.CYAN);
+        mForegroundColors.put(State.ACTIVE, Color.YELLOW);
+        mBackgroundColors.put(State.CALL, Color.BLUE);
+        mForegroundColors.put(State.CALL, Color.YELLOW);
+        mBackgroundColors.put(State.CONTROL, Color.ORANGE);
+        mForegroundColors.put(State.CONTROL, Color.BLUE);
+        mBackgroundColors.put(State.DATA, Color.GREEN);
+        mForegroundColors.put(State.DATA, Color.BLUE);
+        mBackgroundColors.put(State.ENCRYPTED, Color.MAGENTA);
+        mForegroundColors.put(State.ENCRYPTED, Color.WHITE);
+        mBackgroundColors.put(State.FADE, Color.LIGHT_GRAY);
+        mForegroundColors.put(State.FADE, Color.DARK_GRAY);
+        mBackgroundColors.put(State.IDLE, Color.WHITE);
+        mForegroundColors.put(State.IDLE, Color.DARK_GRAY);
+        mBackgroundColors.put(State.OVERFLOW, Color.RED);
+        mForegroundColors.put(State.OVERFLOW, Color.YELLOW);
+        mBackgroundColors.put(State.RESET, Color.PINK);
+        mForegroundColors.put(State.RESET, Color.YELLOW);
+        mBackgroundColors.put(State.TEARDOWN, Color.DARK_GRAY);
+        mForegroundColors.put(State.TEARDOWN, Color.WHITE);
     }
 
     @Override
@@ -185,44 +216,14 @@ public class ChannelMetadataPanel extends JPanel implements ListSelectionListene
                 State state = (State)value;
                 label.setText(state.getDisplayValue());
 
-                switch(state)
+                if(mBackgroundColors.containsKey(state))
                 {
-                    case CALL:
-                        background = SystemProperties.getInstance().get(PROPERTY_PREFIX_BACKGROUND + "call", Color.BLUE);
-                        foreground = SystemProperties.getInstance().get(PROPERTY_PREFIX_FOREGROUND + "call", Color.YELLOW);
-                        break;
-                    case CONTROL:
-                        background = SystemProperties.getInstance().get(PROPERTY_PREFIX_BACKGROUND + "control", Color.ORANGE);
-                        foreground = SystemProperties.getInstance().get(PROPERTY_PREFIX_FOREGROUND + "control", Color.BLUE);
-                        break;
-                    case DATA:
-                        background = SystemProperties.getInstance().get(PROPERTY_PREFIX_BACKGROUND + "data", Color.GREEN);
-                        foreground = SystemProperties.getInstance().get(PROPERTY_PREFIX_FOREGROUND + "data", Color.BLUE);
-                        break;
-                    case ENCRYPTED:
-                        background = SystemProperties.getInstance().get(PROPERTY_PREFIX_BACKGROUND + "encrypted", Color.MAGENTA);
-                        foreground = SystemProperties.getInstance().get(PROPERTY_PREFIX_FOREGROUND + "encrypted", Color.WHITE);
-                        break;
-                    case FADE:
-                        background = SystemProperties.getInstance().get(PROPERTY_PREFIX_BACKGROUND + "fade", Color.LIGHT_GRAY.BLUE);
-                        foreground = SystemProperties.getInstance().get(PROPERTY_PREFIX_FOREGROUND + "fade", Color.YELLOW);
-                        break;
-                    case IDLE:
-                        background = SystemProperties.getInstance().get(PROPERTY_PREFIX_BACKGROUND + "idle", Color.WHITE);
-                        foreground = SystemProperties.getInstance().get(PROPERTY_PREFIX_FOREGROUND + "idle", Color.BLUE);
-                        break;
-                    case OVERFLOW:
-                        background = SystemProperties.getInstance().get(PROPERTY_PREFIX_BACKGROUND + "overflow", Color.RED);
-                        foreground = SystemProperties.getInstance().get(PROPERTY_PREFIX_FOREGROUND + "overflow", Color.YELLOW);
-                        break;
-                    case RESET:
-                        background = SystemProperties.getInstance().get(PROPERTY_PREFIX_BACKGROUND + "reset", Color.PINK);
-                        foreground = SystemProperties.getInstance().get(PROPERTY_PREFIX_FOREGROUND + "reset", Color.YELLOW);
-                        break;
-                    case TEARDOWN:
-                        background = SystemProperties.getInstance().get(PROPERTY_PREFIX_BACKGROUND + "teardown", Color.DARK_GRAY);
-                        foreground = SystemProperties.getInstance().get(PROPERTY_PREFIX_FOREGROUND + "teardown", Color.WHITE);
-                        break;
+                    background = mBackgroundColors.get(state);
+                }
+
+                if(mForegroundColors.containsKey(state))
+                {
+                    foreground = mForegroundColors.get(state);
                 }
             }
             else

src/main/java/io/github/dsheirer/channel/metadata/ChannelMetadataViewer.java

@@ -26,11 +26,10 @@ import io.github.dsheirer.icon.IconManager;
 import io.github.dsheirer.module.decode.event.CallEventPanel;
 import io.github.dsheirer.module.decode.event.MessageActivityPanel;
 import io.github.dsheirer.settings.SettingsManager;
-import io.github.dsheirer.spectrum.ChannelSpectrumPanel;
 import net.miginfocom.swing.MigLayout;
 
-import javax.swing.*;
-import java.awt.*;
+import javax.swing.JPanel;
+import java.awt.Color;
 
 public class ChannelMetadataViewer extends JPanel
 {
@@ -39,7 +38,6 @@ public class ChannelMetadataViewer extends JPanel
     private ChannelDetailPanel mChannelDetailPanel;
     private CallEventPanel mCallEventPanel;
     private MessageActivityPanel mMessageActivityPanel;
-    private ChannelSpectrumPanel mChannelSpectrumPanel;
 
     /**
      * GUI panel that combines the currently decoding channels metadata table and viewers for channel details,
@@ -51,7 +49,6 @@ public class ChannelMetadataViewer extends JPanel
         mChannelDetailPanel = new ChannelDetailPanel(channelProcessingManager);
         mCallEventPanel = new CallEventPanel(iconManager);
         mMessageActivityPanel = new MessageActivityPanel(channelProcessingManager);
-//        mChannelSpectrumPanel = new ChannelSpectrumPanel(settingsManager, channelProcessingManager);
         mChannelMetadataPanel = new ChannelMetadataPanel(channelProcessingManager, iconManager);
 
         init();

src/main/java/io/github/dsheirer/channel/state/AlwaysUnsquelchedDecoderState.java

@@ -25,8 +25,6 @@ import io.github.dsheirer.module.decode.DecoderType;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.util.concurrent.ScheduledExecutorService;
-
 /**
  * Basic decoder channel state - provides the minimum channel state functionality
  * to support an always un-squelched audio decoder.
@@ -94,7 +92,7 @@ public class AlwaysUnsquelchedDecoderState extends DecoderState
     }
 
     @Override
-    public void start(ScheduledExecutorService executor)
+    public void start()
     {
         broadcast(new AttributeChangeRequest<String>(Attribute.PRIMARY_ADDRESS_TO, NO_SQUELCH));
         broadcast(new DecoderStateEvent(this, Event.ALWAYS_UNSQUELCH, State.IDLE));

src/main/java/io/github/dsheirer/channel/state/ChannelState.java

@@ -20,8 +20,6 @@ package io.github.dsheirer.channel.state;
 
 import io.github.dsheirer.audio.squelch.ISquelchStateProvider;
 import io.github.dsheirer.audio.squelch.SquelchState;
-import io.github.dsheirer.channel.heartbeat.Heartbeat;
-import io.github.dsheirer.channel.heartbeat.IHeartbeatListener;
 import io.github.dsheirer.channel.metadata.Attribute;
 import io.github.dsheirer.channel.metadata.AttributeChangeRequest;
 import io.github.dsheirer.channel.metadata.IAttributeChangeRequestListener;
@@ -34,20 +32,19 @@ import io.github.dsheirer.module.decode.DecoderType;
 import io.github.dsheirer.module.decode.config.DecodeConfiguration;
 import io.github.dsheirer.module.decode.event.CallEvent;
 import io.github.dsheirer.module.decode.event.ICallEventProvider;
+import io.github.dsheirer.sample.IOverflowListener;
 import io.github.dsheirer.sample.Listener;
-import io.github.dsheirer.sample.real.IOverflowListener;
-import io.github.dsheirer.source.tuner.frequency.FrequencyChangeEvent;
-import io.github.dsheirer.source.tuner.frequency.IFrequencyChangeListener;
+import io.github.dsheirer.source.ISourceEventListener;
+import io.github.dsheirer.source.ISourceEventProvider;
+import io.github.dsheirer.source.SourceEvent;
+import io.github.dsheirer.source.heartbeat.Heartbeat;
+import io.github.dsheirer.source.heartbeat.IHeartbeatListener;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.util.concurrent.ScheduledExecutorService;
-
-import static io.github.dsheirer.source.tuner.frequency.FrequencyChangeEvent.Event.NOTIFICATION_FREQUENCY_CHANGE;
-
 public class ChannelState extends Module implements ICallEventProvider, IDecoderStateEventListener,
-    IDecoderStateEventProvider, IFrequencyChangeListener, IHeartbeatListener, ISquelchStateProvider,
-    IAttributeChangeRequestListener, IOverflowListener
+    IDecoderStateEventProvider, ISourceEventListener, ISourceEventProvider, IHeartbeatListener,
+    ISquelchStateProvider, IAttributeChangeRequestListener, IOverflowListener
 {
     private final static Logger mLog = LoggerFactory.getLogger(ChannelState.class);
 
@@ -59,12 +56,13 @@ public class ChannelState extends Module implements ICallEventProvider, IDecoder
     private Listener<CallEvent> mCallEventListener;
     private Listener<DecoderStateEvent> mDecoderStateListener;
     private Listener<SquelchState> mSquelchStateListener;
+    private Listener<SourceEvent> mExternalSourceEventListener;
     private DecoderStateEventReceiver mDecoderStateEventReceiver = new DecoderStateEventReceiver();
     private HeartbeatReceiver mHeartbeatReceiver = new HeartbeatReceiver();
     private ChannelType mChannelType;
     private TrafficChannelManager mTrafficChannelEndListener;
     private CallEvent mTrafficChannelCallEvent;
-    private FrequencyChangeListener mFrequencyChangeListener;
+    private SourceEventListener mInternalSourceEventListener;
 
     private boolean mSquelchLocked = false;
     private boolean mSelected = false;
@@ -124,7 +122,7 @@ public class ChannelState extends Module implements ICallEventProvider, IDecoder
     }
 
     @Override
-    public void start(ScheduledExecutorService executor)
+    public void start()
     {
         mMutableMetadata.receive(new AttributeChangeRequest<State>(Attribute.CHANNEL_STATE, mState));
 
@@ -150,6 +148,8 @@ public class ChannelState extends Module implements ICallEventProvider, IDecoder
         mTrafficChannelCallEvent = null;
 
         mSquelchLocked = false;
+
+        setState(State.TEARDOWN);
     }
 
     public void dispose()
@@ -160,14 +160,14 @@ public class ChannelState extends Module implements ICallEventProvider, IDecoder
     }
 
     @Override
-    public Listener<FrequencyChangeEvent> getFrequencyChangeListener()
+    public Listener<SourceEvent> getSourceEventListener()
     {
-        if(mFrequencyChangeListener == null)
+        if(mInternalSourceEventListener == null)
         {
-            mFrequencyChangeListener = new FrequencyChangeListener();
+            mInternalSourceEventListener = new SourceEventListener();
         }
 
-        return mFrequencyChangeListener;
+        return mInternalSourceEventListener;
     }
 
     private boolean isStandardChannel()
@@ -257,6 +257,17 @@ public class ChannelState extends Module implements ICallEventProvider, IDecoder
         }
     }
 
+    /**
+     * Broadcasts the source event to a registered external source event listener
+     */
+    protected void broadcast(SourceEvent sourceEvent)
+    {
+        if(mExternalSourceEventListener != null)
+        {
+            mExternalSourceEventListener.receive(sourceEvent);
+        }
+    }
+
     /**
      * Sets the squelch state listener
      */
@@ -294,6 +305,11 @@ public class ChannelState extends Module implements ICallEventProvider, IDecoder
         {
             switch(state)
             {
+                case ACTIVE:
+                    broadcast(SquelchState.SQUELCH);
+                    updateFadeTimeout();
+                    mState = state;
+                    break;
                 case CONTROL:
                     //Don't allow traffic channels to be control channels, otherwise they can't transition to teardown
                     if(isStandardChannel())
@@ -518,18 +534,46 @@ public class ChannelState extends Module implements ICallEventProvider, IDecoder
     }
 
     /**
-     * Listener to receive frequency change events and rebroadcast them to the decoder states
+     * Registers the listener to receive source events from the channel state
      */
-    public class FrequencyChangeListener implements Listener<FrequencyChangeEvent>
+    @Override
+    public void setSourceEventListener(Listener<SourceEvent> listener)
+    {
+        mExternalSourceEventListener = listener;
+    }
+
+    /**
+     * De-Registers a listener from receiving source events from the channel state
+     */
+    @Override
+    public void removeSourceEventListener()
+    {
+        mExternalSourceEventListener = null;
+    }
+
+    /**
+     * Listener to receive source events.
+     */
+    public class SourceEventListener implements Listener<SourceEvent>
     {
         @Override
-        public void receive(FrequencyChangeEvent frequencyChangeEvent)
+        public void receive(SourceEvent sourceEvent)
         {
-            if(frequencyChangeEvent.getEvent() == NOTIFICATION_FREQUENCY_CHANGE)
+            switch(sourceEvent.getEvent())
             {
-                long frequency = frequencyChangeEvent.getValue().longValue();
-
-                broadcast(new DecoderStateEvent(this, Event.SOURCE_FREQUENCY, getState(), frequency));
+                case NOTIFICATION_FREQUENCY_CHANGE:
+                    //Rebroadcast source frequency change events for the decoder(s) to process
+                    long frequency = sourceEvent.getValue().longValue();
+                    broadcast(new DecoderStateEvent(this, Event.SOURCE_FREQUENCY, getState(), frequency));
+                    break;
+                case NOTIFICATION_MEASURED_FREQUENCY_ERROR:
+                    //Rebroadcast frequency error measurements to external listener if we're currently
+                    //in an active (ie sync locked) state.
+                    if(getState().isActiveState())
+                    {
+                        broadcast(SourceEvent.frequencyErrorMeasurementSyncLocked(sourceEvent.getValue().longValue(), mChannelType.name()));
+                    }
+                    break;
             }
         }
     }

src/main/java/io/github/dsheirer/channel/state/State.java

@@ -24,54 +24,114 @@ import java.util.EnumSet;
  */
 public enum State
 {
-    IDLE("IDLE")
+    /**
+     * Active state indicates that valid messages are being decoded that do not indicate any call or data
+     * activity.  For example, this is used for P25 when a channel is actively transmitting Terminator Data
+     * Units in between data packets or at the beginning or end of a call.
+     */
+    ACTIVE("ACTIVE")
         {
             @Override
             public boolean canChangeTo(State state)
             {
-                return state != TEARDOWN && state != RESET && state != OVERFLOW;
+                return state == CALL |
+                       state == CONTROL ||
+                       state == DATA ||
+                       state == ENCRYPTED ||
+                       state == FADE ||
+                       state == TEARDOWN;
             }
         },
+    /**
+     * Indicates that call messages are being decoded, or a call is in progress (ie producing audio).
+     */
     CALL("CALL")
         {
             @Override
             public boolean canChangeTo(State state)
             {
-                return state == CONTROL || state == DATA || state == ENCRYPTED || state == FADE || state == TEARDOWN;
-            }
-        },
-    DATA("DATA")
-        {
-            @Override
-            public boolean canChangeTo(State state)
-            {
-                return state == CALL || state == CONTROL || state == ENCRYPTED || state == FADE || state == TEARDOWN;
-            }
-        },
-    ENCRYPTED("ENCRYPTED")
-        {
-            @Override
-            public boolean canChangeTo(State state)
-            {
-                return state == FADE || state == TEARDOWN;
+                return state == ACTIVE ||
+                       state == CONTROL ||
+                       state == DATA ||
+                       state == ENCRYPTED ||
+                       state == FADE ||
+                       state == TEARDOWN;
             }
         },
+    /**
+     * Indicates a trunking control channel is being decoded.
+     */
     CONTROL("CONTROL")
         {
             @Override
             public boolean canChangeTo(State state)
             {
-                return state == IDLE || state == FADE;
+                return state == IDLE ||
+                       state == FADE;
             }
         },
+    /**
+     * Indicates data packets are being decoded
+     */
+    DATA("DATA")
+        {
+            @Override
+            public boolean canChangeTo(State state)
+            {
+                return state == ACTIVE ||
+                       state == CALL ||
+                       state == CONTROL ||
+                       state == ENCRYPTED ||
+                       state == FADE ||
+                       state == TEARDOWN;
+            }
+        },
+    /**
+     * Indicates encrypted audio is detected.
+     */
+    ENCRYPTED("ENCRYPTED")
+        {
+            @Override
+            public boolean canChangeTo(State state)
+            {
+                return state == FADE ||
+                       state == TEARDOWN;
+            }
+        },
+    /**
+     * Fade state occurs when the channel is no longer actively decoding an messages.  This is a transitory
+     * state before transition to IDLE or back to an active state.
+     */
     FADE("FADE")
         {
             @Override
             public boolean canChangeTo(State state)
             {
-                return state != FADE && state != RESET && state != OVERFLOW;
+                return state != FADE &&
+                       state != RESET &&
+                       state != OVERFLOW;
             }
         },
+    /**
+     * Indicates the channel is idle and not actively decoding any messages
+     */
+    IDLE("IDLE")
+        {
+            @Override
+            public boolean canChangeTo(State state)
+            {
+                return state != TEARDOWN &&
+                       state != RESET &&
+                       state != OVERFLOW;
+            }
+        },
+    /**
+     * Indicates that the channel's sample buffer has overflowed and new buffer samples are no longer being
+     * delivered to the channel.  This state persists until the processing catches up and reduces the number
+     * of samples in the input buffer below a threshold value.  Transition to and from this state is exclusively
+     * managed by the Channel State and no other channel states can be processed from the channel decoders
+     * until the channel state is taken out of overflow.
+     */
     OVERFLOW("OVERFLOW")
         {
             @Override
@@ -80,6 +140,9 @@ public enum State
                 return false;
             }
         },
+    /**
+     * Indicates that the channel has been reset and is ready to use for a new decoding session.
+     */
     RESET("RESET")
         {
             @Override
@@ -88,6 +151,10 @@ public enum State
                 return state == IDLE;
             }
         },
+    /**
+     * Call or data teardown.  This state is used by traffic channels to indicate that a call or data session
+     * has concluded and the channel is ready for tear down and reuse.
+     */
     TEARDOWN("TEARDOWN")
         {
             @Override
@@ -99,7 +166,7 @@ public enum State
 
     private String mDisplayValue;
 
-    public static final EnumSet<State> CALL_STATES = EnumSet.of(CALL, CONTROL, DATA, ENCRYPTED);
+    public static final EnumSet<State> CALL_STATES = EnumSet.of(ACTIVE, CALL, CONTROL, DATA, ENCRYPTED);
     public static final EnumSet<State> IDLE_STATES = EnumSet.of(IDLE, FADE);
 
     private State(String displayValue)
@@ -109,6 +176,17 @@ public enum State
 
     public abstract boolean canChangeTo(State state);
 
+    /**
+     * Indicates that this state is an active (ie decoding) state and is one of the states
+     * enumerated in the CALL_STATES enumeration set.
+     *
+     * @return true if this state is an active state
+     */
+    public boolean isActiveState()
+    {
+        return CALL_STATES.contains(this);
+    }
+
     public String getDisplayValue()
     {
         return mDisplayValue;

src/main/java/io/github/dsheirer/channel/traffic/TrafficChannelManager.java

@@ -1,19 +1,16 @@
 /*******************************************************************************
- * sdrtrunk
+ * sdr-trunk
  * Copyright (C) 2014-2017 Dennis Sheirer
  *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
  *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
  *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
  *
  ******************************************************************************/
 package io.github.dsheirer.channel.traffic;
@@ -29,13 +26,12 @@ import io.github.dsheirer.controller.channel.TrafficChannelEvent;
 import io.github.dsheirer.module.Module;
 import io.github.dsheirer.module.decode.config.DecodeConfiguration;
 import io.github.dsheirer.module.decode.event.CallEvent;
+import io.github.dsheirer.module.decode.event.CallEvent.CallEventType;
 import io.github.dsheirer.module.decode.event.ICallEventProvider;
-import io.github.dsheirer.module.log.config.EventLogConfiguration;
 import io.github.dsheirer.record.config.RecordConfiguration;
 import io.github.dsheirer.sample.Listener;
 import io.github.dsheirer.source.config.SourceConfigTuner;
-import io.github.dsheirer.source.tuner.TunerChannel;
-import io.github.dsheirer.source.tuner.TunerChannel.Type;
+import io.github.dsheirer.source.tuner.channel.TunerChannel;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -43,7 +39,6 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ScheduledExecutorService;
 
 public class TrafficChannelManager extends Module implements ICallEventProvider, IDecoderStateEventListener
 {
@@ -61,7 +56,6 @@ public class TrafficChannelManager extends Module implements ICallEventProvider,
 
     private ChannelModel mChannelModel;
     private DecodeConfiguration mDecodeConfiguration;
-    private EventLogConfiguration mEventLogConfiguration;
     private RecordConfiguration mRecordConfiguration;
     private String mSystem;
     private String mSite;
@@ -75,7 +69,6 @@ public class TrafficChannelManager extends Module implements ICallEventProvider,
      * @param channelModel containing channels currently in use
      * @param decodeConfiguration - decoder configuration to use for each
      * traffic channel allocation.
-     * @param eventLogConfiguration - logging configuration to use for traffic channels
      * @param recordConfiguration - recording options for each traffic channel
      * @param system label to use to describe the system
      * @param site label to use to describe the site
@@ -85,7 +78,6 @@ public class TrafficChannelManager extends Module implements ICallEventProvider,
      */
     public TrafficChannelManager(ChannelModel channelModel,
                                  DecodeConfiguration decodeConfiguration,
-                                 EventLogConfiguration eventLogConfiguration,
                                  RecordConfiguration recordConfiguration,
                                  String system,
                                  String site,
@@ -94,7 +86,6 @@ public class TrafficChannelManager extends Module implements ICallEventProvider,
     {
         mChannelModel = channelModel;
         mDecodeConfiguration = decodeConfiguration;
-        mEventLogConfiguration = eventLogConfiguration;
         mRecordConfiguration = recordConfiguration;
         mSystem = system;
         mSite = site;
@@ -150,8 +141,6 @@ public class TrafficChannelManager extends Module implements ICallEventProvider,
 
                 channel.setDecodeConfiguration(mDecodeConfiguration);
 
-                channel.setEventLogConfiguration(mEventLogConfiguration);
-
                 channel.setRecordConfiguration(mRecordConfiguration);
 
                 channel.setAliasListName(mAliasListName);
@@ -161,7 +150,7 @@ public class TrafficChannelManager extends Module implements ICallEventProvider,
                 mTrafficChannelPool.add(channel);
             }
 
-			/* If we have a configured channel, update metadata */
+            /* If we have a configured channel, update metadata */
             if(channel != null)
             {
                 channel.setSourceConfiguration(new SourceConfigTuner(tunerChannel));
@@ -184,7 +173,7 @@ public class TrafficChannelManager extends Module implements ICallEventProvider,
     {
         CallEvent callEvent = event.getCallEvent();
 
-		/* Check for duplicate events and suppress */
+        /* Check for duplicate events and suppress */
         synchronized(mTrafficChannelsInUse)
         {
             if(mTrafficChannelsInUse.containsKey(callEvent.getChannel()))
@@ -196,8 +185,8 @@ public class TrafficChannelManager extends Module implements ICallEventProvider,
 
             if(frequency > 0)
             {
-                Channel channel = getChannel(callEvent.getChannel(), new TunerChannel(Type.TRAFFIC,
-                    frequency, mDecodeConfiguration.getDecoderType().getChannelBandwidth()));
+                Channel channel = getChannel(callEvent.getChannel(), new TunerChannel(frequency,
+                    mDecodeConfiguration.getDecoderType().getChannelBandwidth()));
 
                 if(channel != null)
                 {
@@ -213,7 +202,7 @@ public class TrafficChannelManager extends Module implements ICallEventProvider,
                     }
                     else
                     {
-                        callEvent.setCallEventType(CallEvent.CallEventType.CALL_DETECT);
+                        callEvent.setCallEventType(CallEventType.CALL_DETECT);
 
                         String details = callEvent.getDetails();
 
@@ -230,7 +219,7 @@ public class TrafficChannelManager extends Module implements ICallEventProvider,
                 }
                 else
                 {
-                    callEvent.setCallEventType(CallEvent.CallEventType.CALL_DETECT);
+                    callEvent.setCallEventType(CallEventType.CALL_DETECT);
 
                     String details = callEvent.getDetails();
 
@@ -247,7 +236,7 @@ public class TrafficChannelManager extends Module implements ICallEventProvider,
             }
             else
             {
-                callEvent.setCallEventType(CallEvent.CallEventType.CALL_DETECT);
+                callEvent.setCallEventType(CallEventType.CALL_DETECT);
 
                 String details = callEvent.getDetails();
 
@@ -337,7 +326,7 @@ public class TrafficChannelManager extends Module implements ICallEventProvider,
     }
 
     @Override
-    public void start(ScheduledExecutorService executor)
+    public void start()
     {
     }
 
@@ -348,7 +337,7 @@ public class TrafficChannelManager extends Module implements ICallEventProvider,
         {
             List<String> channels = new ArrayList<>();
 
-			/* Copy the keyset so we don't get concurrent modification of the map */
+            /* Copy the keyset so we don't get concurrent modification of the map */
             channels.addAll(mTrafficChannelsInUse.keySet());
 
             for(String channel : channels)
@@ -399,4 +388,4 @@ public class TrafficChannelManager extends Module implements ICallEventProvider,
             }
         }
     }
-}
+}

src/main/java/io/github/dsheirer/controller/channel/Channel.java

@@ -31,18 +31,16 @@ import io.github.dsheirer.module.log.config.EventLogConfiguration;
 import io.github.dsheirer.record.RecorderType;
 import io.github.dsheirer.record.config.RecordConfiguration;
 import io.github.dsheirer.sample.Listener;
+import io.github.dsheirer.source.SourceEvent;
 import io.github.dsheirer.source.SourceType;
 import io.github.dsheirer.source.config.SourceConfigFactory;
 import io.github.dsheirer.source.config.SourceConfigRecording;
 import io.github.dsheirer.source.config.SourceConfigTuner;
 import io.github.dsheirer.source.config.SourceConfiguration;
-import io.github.dsheirer.source.tuner.TunerChannel;
-import io.github.dsheirer.source.tuner.TunerChannel.Type;
-import io.github.dsheirer.source.tuner.frequency.FrequencyChangeEvent;
-import io.github.dsheirer.source.tuner.frequency.FrequencyChangeEvent.Event;
+import io.github.dsheirer.source.tuner.channel.TunerChannel;
 
 @JacksonXmlRootElement(localName = "channel")
-public class Channel extends Configuration implements Listener<FrequencyChangeEvent>
+public class Channel extends Configuration implements Listener<SourceEvent>
 {
     // Standard channels are persisted and traffic channels are temporary
     public enum ChannelType
@@ -490,15 +488,14 @@ public class Channel extends Configuration implements Listener<FrequencyChangeEv
             {
                 SourceConfigTuner config = (SourceConfigTuner)mSourceConfiguration;
 
-                mTunerChannel = new TunerChannel(Type.LOCKED, config.getFrequency(),
+                mTunerChannel = new TunerChannel(config.getFrequency(),
                     mDecodeConfiguration.getDecoderType().getChannelBandwidth());
             }
             else if(mSourceConfiguration.getSourceType() == SourceType.RECORDING)
             {
-                SourceConfigRecording config =
-                    (SourceConfigRecording)mSourceConfiguration;
+                SourceConfigRecording config = (SourceConfigRecording)mSourceConfiguration;
 
-                mTunerChannel = new TunerChannel(Type.LOCKED, config.getFrequency(),
+                mTunerChannel = new TunerChannel(config.getFrequency(),
                     mDecodeConfiguration.getDecoderType().getChannelBandwidth());
             }
         }
@@ -524,9 +521,9 @@ public class Channel extends Configuration implements Listener<FrequencyChangeEv
      * be used to visually show in the spectral display.
      */
     @Override
-    public void receive(FrequencyChangeEvent event)
+    public void receive(SourceEvent event)
     {
-        if(event.getEvent() == Event.NOTIFICATION_CHANNEL_FREQUENCY_CORRECTION_CHANGE)
+        if(event.getEvent() == SourceEvent.Event.NOTIFICATION_CHANNEL_FREQUENCY_CORRECTION_CHANGE)
         {
             mChannelFrequencyCorrection = event.getValue().intValue();
         }

src/main/java/io/github/dsheirer/controller/channel/ChannelController.java

@@ -1,3 +1,18 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
 package io.github.dsheirer.controller.channel;
 
 import com.jidesoft.swing.JideSplitPane;
@@ -24,8 +39,7 @@ import java.awt.Rectangle;
 import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;
 
-public class ChannelController extends JPanel 
-				implements ActionListener, ListSelectionListener
+public class ChannelController extends JPanel implements ActionListener, ListSelectionListener
 {
 	private static final long serialVersionUID = 1L;
 
@@ -168,9 +182,13 @@ public class ChannelController extends JPanel
 		if( index >= 0 )
 		{
 			int translatedIndex = mChannelTable.convertRowIndexToView( index );
-			mChannelTable.setRowSelectionInterval( translatedIndex, translatedIndex );
-			mChannelTable.scrollRectToVisible( 
-				new Rectangle( mChannelTable.getCellRect( translatedIndex, 0, true ) ) );
+
+			if(translatedIndex >= 0)
+			{
+				mChannelTable.setRowSelectionInterval( translatedIndex, translatedIndex );
+				mChannelTable.scrollRectToVisible(
+					new Rectangle( mChannelTable.getCellRect( translatedIndex, 0, true ) ) );
+			}
 		}
 	}
 	

src/main/java/io/github/dsheirer/controller/channel/ChannelProcessingManager.java

@@ -19,7 +19,6 @@
 package io.github.dsheirer.controller.channel;
 
 import io.github.dsheirer.alias.AliasModel;
-import io.github.dsheirer.audio.AudioPacket;
 import io.github.dsheirer.channel.metadata.Attribute;
 import io.github.dsheirer.channel.metadata.AttributeChangeRequest;
 import io.github.dsheirer.channel.metadata.ChannelMetadataModel;
@@ -34,7 +33,9 @@ import io.github.dsheirer.module.decode.event.MessageActivityModel;
 import io.github.dsheirer.module.log.EventLogManager;
 import io.github.dsheirer.record.RecorderManager;
 import io.github.dsheirer.record.RecorderType;
+import io.github.dsheirer.record.binary.BinaryRecorder;
 import io.github.dsheirer.sample.Listener;
+import io.github.dsheirer.sample.buffer.ReusableAudioPacket;
 import io.github.dsheirer.source.Source;
 import io.github.dsheirer.source.SourceException;
 import io.github.dsheirer.source.SourceManager;
@@ -54,7 +55,7 @@ public class ChannelProcessingManager implements ChannelEventListener
 
     private Map<Integer,ProcessingChain> mProcessingChains = new HashMap<>();
 
-    private List<Listener<AudioPacket>> mAudioPacketListeners = new CopyOnWriteArrayList<>();
+    private List<Listener<ReusableAudioPacket>> mAudioPacketListeners = new CopyOnWriteArrayList<>();
     private List<Listener<Message>> mMessageListeners = new CopyOnWriteArrayList<>();
 
     private ChannelModel mChannelModel;
@@ -211,7 +212,8 @@ public class ChannelProcessingManager implements ChannelEventListener
         try
         {
             source = mSourceManager.getSource(channel.getSourceConfiguration(),
-                channel.getDecodeConfiguration().getDecoderType().getChannelBandwidth());
+                channel.getDecodeConfiguration().getDecoderType().getChannelBandwidth(),
+                channel.getDecodeConfiguration().getDecoderType().getChannelSpecification());
         }
         catch(SourceException se)
         {
@@ -232,7 +234,7 @@ public class ChannelProcessingManager implements ChannelEventListener
             processingChain = new ProcessingChain(channel.getChannelType());
 
 			/* Register global listeners */
-            for(Listener<AudioPacket> listener : mAudioPacketListeners)
+            for(Listener<ReusableAudioPacket> listener : mAudioPacketListeners)
             {
                 processingChain.addAudioPacketListener(listener);
             }
@@ -308,6 +310,25 @@ public class ChannelProcessingManager implements ChannelEventListener
             {
                 processingChain.addModule(mRecorderManager.getBasebandRecorder(channel.toString()));
             }
+
+            /* Add decoded bit stream recorder if the decoder supports bitstream output */
+            if(DecoderFactory.getBitstreamDecoders().contains(channel.getDecodeConfiguration().getDecoderType()))
+            {
+                if((recorders.contains(RecorderType.DEMODULATED_BIT_STREAM) &&
+                    channel.getChannelType() == Channel.ChannelType.STANDARD))
+                {
+                    processingChain.addModule(new BinaryRecorder(mRecorderManager.getRecordingBasePath(),
+                        channel.toString()));
+                }
+
+                /* Add traffic channel decoded bit stream recorder */
+                if(recorders.contains(RecorderType.TRAFFIC_DEMODULATED_BIT_STREAM) &&
+                    channel.getChannelType() == Channel.ChannelType.TRAFFIC)
+                {
+                    processingChain.addModule(new BinaryRecorder(mRecorderManager.getRecordingBasePath(),
+                        channel.toString()));
+                }
+            }
         }
 
         processingChain.setSource(source);
@@ -363,11 +384,27 @@ public class ChannelProcessingManager implements ChannelEventListener
         }
     }
 
+    /**
+     * Stops all currently processing channels to prepare for shutdown.
+     */
+    public void shutdown()
+    {
+        mLog.debug("Stopping Channels ...");
+        for(Channel channel: mChannelModel.getChannels())
+        {
+            if(channel.isProcessing())
+            {
+                mLog.debug("Stopping channel: " + channel.toString());
+                stopProcessing(channel, true);
+            }
+        }
+    }
+
     /**
      * Adds a message listener that will be added to all channels to receive
      * any messages.
      */
-    public void addAudioPacketListener(Listener<AudioPacket> listener)
+    public void addAudioPacketListener(Listener<ReusableAudioPacket> listener)
     {
         mAudioPacketListeners.add(listener);
     }
@@ -375,7 +412,7 @@ public class ChannelProcessingManager implements ChannelEventListener
     /**
      * Removes a message listener.
      */
-    public void removeAudioPacketListener(Listener<AudioPacket> listener)
+    public void removeAudioPacketListener(Listener<ReusableAudioPacket> listener)
     {
         mAudioPacketListeners.remove(listener);
     }

src/main/java/io/github/dsheirer/dsp/NRZDecoder.java

@@ -1,77 +1,76 @@
 /*******************************************************************************
- *     SDR Trunk 
- *     Copyright (C) 2014 Dennis Sheirer
- * 
- *     This program is free software: you can redistribute it and/or modify
- *     it under the terms of the GNU General Public License as published by
- *     the Free Software Foundation, either version 3 of the License, or
- *     (at your option) any later version.
- * 
- *     This program is distributed in the hope that it will be useful,
- *     but WITHOUT ANY WARRANTY; without even the implied warranty of
- *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *     GNU General Public License for more details.
- * 
- *     You should have received a copy of the GNU General Public License
- *     along with this program.  If not, see <http://www.gnu.org/licenses/>
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
  ******************************************************************************/
 package io.github.dsheirer.dsp;
 
+import io.github.dsheirer.bits.IBinarySymbolProcessor;
 import io.github.dsheirer.sample.Listener;
 
-public class NRZDecoder implements Listener<Boolean>
+public class NRZDecoder implements IBinarySymbolProcessor
 {
-	public final static boolean MODE_NORMAL = true;
-	public final static boolean MODE_INVERTED = false;
-	
-	private Listener<Boolean> mListener;
-	private boolean mMode = MODE_NORMAL;
-	private boolean mPrevious;
+    public final static boolean MODE_NORMAL = true;
+    public final static boolean MODE_INVERTED = false;
 
-	/**
-	 * Non Return To Zero (NRZ) and NRZ Inverted (NRZ-I) Decoder.
-	 * 
-	 * Use default constructor for NRZ output.  Use the alternate constructor
-	 * with the MODE_INVERTED argument for NRZ-I output.
-	 * 
-	 * Performs XOR of incoming bit with previous output and sends the result
-	 * to the registered listener.  
-	 */
-	public NRZDecoder( boolean mode )
-	{
-		mMode = mode;
-	}
-	
-	public NRZDecoder()
-	{
-		this( MODE_NORMAL );
-	}
-	
-	public void dispose()
-	{
-		mListener = null;
-	}
+    private IBinarySymbolProcessor mListener;
+    private boolean mMode = MODE_NORMAL;
+    private boolean mPrevious;
 
-	@Override
-    public void receive( Boolean bit )
+    /**
+     * Non Return To Zero (NRZ) and NRZ Inverted (NRZ-I) Decoder.
+     *
+     * Use default constructor for NRZ output.  Use the alternate constructor
+     * with the MODE_INVERTED argument for NRZ-I output.
+     *
+     * Performs XOR of incoming bit with previous output and sends the result
+     * to the registered listener.
+     */
+    public NRZDecoder(boolean mode)
     {
-		boolean result = mPrevious ^ bit;
-		
-		if( mListener != null )
-		{
-			mListener.receive( mMode ? result : !result );
-		}
-		
-		mPrevious = result;
+        mMode = mode;
     }
 
-	public void setListener( Listener<Boolean> listener )
-	{
-		mListener = listener;
-	}
-	
-	public void removeListener( Listener<Boolean> listener )
-	{
-		mListener = null;
-	}
+    public NRZDecoder()
+    {
+        this(MODE_NORMAL);
+    }
+
+    public void dispose()
+    {
+        mListener = null;
+    }
+
+    @Override
+    public void receive(boolean symbol)
+    {
+        boolean result = mPrevious ^ symbol;
+
+        if(mListener != null)
+        {
+            mListener.receive(mMode ? result : !result);
+        }
+
+        mPrevious = result;
+    }
+
+    public void setListener(IBinarySymbolProcessor listener)
+    {
+        mListener = listener;
+    }
+
+    public void removeListener(Listener<Boolean> listener)
+    {
+        mListener = null;
+    }
 }

src/main/java/io/github/dsheirer/dsp/afsk/AFSK1200Decoder.java

@@ -0,0 +1,252 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.afsk;
+
+import io.github.dsheirer.bits.IBinarySymbolProcessor;
+import io.github.dsheirer.buffer.FloatAveragingBuffer;
+import io.github.dsheirer.dsp.filter.resample.RealResampler;
+import io.github.dsheirer.dsp.mixer.IOscillator;
+import io.github.dsheirer.dsp.mixer.Oscillator;
+import io.github.dsheirer.sample.Listener;
+import io.github.dsheirer.sample.buffer.ReusableFloatBuffer;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Audio Frequency Shift Keying (AFSK) 1200-baud correlation decoder for decoding 8 kHz FM-demodulated audio samples.
+ *
+ * Note: internally the incoming 8 kHz sample rate is resampled to 7200 Hz to be an integral of the 1200 Hz baud rate
+ * which equates to six samples per symbol.  Each symbol is correlated over an eight sample period with correlation
+ * values averaged over a seven correlation value period.
+ *
+ * Provides normal or inverted decoded output.
+ */
+public class AFSK1200Decoder implements Listener<ReusableFloatBuffer>
+{
+    private final static Logger mLog = LoggerFactory.getLogger(AFSK1200Decoder.class);
+
+    public enum Output
+    {
+        NORMAL, INVERTED
+    }
+
+    public static final double SAMPLE_RATE = 7200.0d;
+    public static final int SAMPLES_PER_SYMBOL = 6; //SAMPLE_RATE / 1200 baud;
+
+    //Correlation period of 8 samples works well and should align nicely with SIMD intrinsic vector sizes
+    public static final int CORRELATION_PERIOD = SAMPLES_PER_SYMBOL + 2;
+    public static final int AVERAGING_PERIOD = SAMPLES_PER_SYMBOL + 1;
+    public static final double MARK = 1200.0;
+    public static final double SPACE = 1800.0;
+    public static final float TIMING_ERROR_GAIN = 1.0f / 3.0f; //Timing error adjustments over 3 symbol periods
+
+    private Correlator mCorrelatorMark = new Correlator(SAMPLE_RATE, MARK, AVERAGING_PERIOD, CORRELATION_PERIOD);
+    private Correlator mCorrelatorSpace = new Correlator(SAMPLE_RATE, SPACE, AVERAGING_PERIOD, CORRELATION_PERIOD);
+    private float[] mCorrelationValuesMark;
+    private float[] mCorrelationValuesSpace;
+
+    protected boolean mNormalOutput;
+    protected float mSymbolTimingGain = TIMING_ERROR_GAIN;
+    protected AFSKSampleBuffer mSampleBuffer;
+    protected AFSKTimingErrorDetector mTimingErrorDetector = new AFSKTimingErrorDetector(SAMPLES_PER_SYMBOL);
+    protected IBinarySymbolProcessor mBinarySymbolProcessor;
+    private boolean mSampleDecision;
+
+    //Resample to an integral of the baud rate 1200 baud * 6 samples per symbol = 7200.0 Hertz
+    private RealResampler mResampler = new RealResampler(8000.0, SAMPLE_RATE, 2000, 1);
+
+    /**
+     * Constructs a decoder using the provided arguments.
+     *
+     * @param sampleBuffer for storing incoming samples and calculating symbols
+     * @param detector for timing error alignment
+     * @param output NORMAL: 1200Hz = Mark(1) and 1800Hz = Space(0), or INVERTED (vice-versa)
+     */
+    public AFSK1200Decoder(AFSKSampleBuffer sampleBuffer, AFSKTimingErrorDetector detector, Output output)
+    {
+        mTimingErrorDetector = detector;
+        mSampleBuffer = sampleBuffer;
+        mSampleBuffer.setTimingGain(mSymbolTimingGain);
+        mResampler.setListener(new Decoder());
+        mNormalOutput = (output == Output.NORMAL);
+    }
+
+    /**
+     * Constructs a decoder using the provided arguments.
+     *
+     * @param output NORMAL: 1200Hz = Mark(1) and 1800Hz = Space(0), or INVERTED (vice-versa)
+     */
+    public AFSK1200Decoder(Output output)
+    {
+        this(new AFSKSampleBuffer(SAMPLES_PER_SYMBOL, TIMING_ERROR_GAIN),
+            new AFSKTimingErrorDetector(SAMPLES_PER_SYMBOL), output);
+    }
+
+    /**
+     * Disposes of all references to prepare for garbage collection
+     */
+    public void dispose()
+    {
+    }
+
+    /**
+     * Processes the buffer samples by converting all samples to boolean values reflecting if the sample value is
+     * greater than zero (or not).  Average symbol timing offset is calculated for the full buffer and the offset is
+     * adjusted and then each of the symbols are decoded using a simple majority decision.
+     *
+     * @param buffer containing 8.0 kHz unfiltered FM demodulated audio samples with sub-audible LTR signalling.
+     */
+    @Override
+    public void receive(ReusableFloatBuffer buffer)
+    {
+        mResampler.resample(buffer);
+    }
+
+    protected void dispatch(boolean symbol)
+    {
+        if(mBinarySymbolProcessor != null)
+        {
+            mBinarySymbolProcessor.receive(mNormalOutput ? symbol : !symbol);
+        }
+    }
+
+    /**
+     * Registers a listener to receive decoded LTR symbols.
+     *
+     * @param binarySymbolProcessor to receive symbols.
+     */
+    public void setSymbolProcessor(IBinarySymbolProcessor binarySymbolProcessor)
+    {
+        mBinarySymbolProcessor = binarySymbolProcessor;
+    }
+
+    /**
+     * Removes the symbol listener from receiving decoded LTR symbols.
+     */
+    public void removeListener()
+    {
+        mBinarySymbolProcessor = null;
+    }
+
+
+    public class Decoder implements Listener<ReusableFloatBuffer>
+    {
+        @Override
+        public void receive(ReusableFloatBuffer buffer)
+        {
+            //Calculate correlation values against each 1200/1800 reference signal
+            mCorrelationValuesMark = mCorrelatorMark.process(buffer);
+            mCorrelationValuesSpace = mCorrelatorSpace.process(buffer);
+
+            buffer.decrementUserCount();
+
+            for(int x = 0; x < mCorrelationValuesMark.length; x++)
+            {
+                //1200 = Mark (1) and 1800 = Space (0)
+                mSampleDecision = mCorrelationValuesMark[x] > mCorrelationValuesSpace[x];
+                mSampleBuffer.receive(mSampleDecision);
+                mTimingErrorDetector.receive(mSampleDecision);
+
+                if(mSampleBuffer.hasSymbol())
+                {
+                    dispatch(mSampleBuffer.getSymbol());
+                    mSampleBuffer.resetAndAdjust(mTimingErrorDetector.getError());
+                }
+            }
+        }
+    }
+
+    /**
+     * Generates a correlation value for each FM demodulated sample against samples generated for an established
+     * reference frequency, correlated and averaged over separate periods relative to the samples per symbol period.
+     *
+     * The sample rate of the correlator should be an integral value of the target frequency for optimal performance,
+     * This correlator only works across integral sample periods and does not provide intra-sample interpolation.
+     *
+     * Correlation period (ie number of samples) should be relative to the samples per symbol.  You may have to
+     * experiment with various values of (samplesPerSymbol +/- 1, 2 or 3) to obtain the optimal decoder performance.
+     *
+     * Averaging period defines the number of correlation values to average before producing the final correlation
+     * value for each sample.
+     */
+    public class Correlator
+    {
+        private FloatAveragingBuffer mAveragingBuffer;
+        private float[] mReferenceSamples;
+        private float[] mDemodulatedSamples;
+        private float[] mCorrelationValues;
+        private float mCorrelationAccumulator;
+
+        /**
+         * Constructs a correlator instance,
+         *
+         * @param sampleRate of the incoming sample stream.  Note: this should be an integral of the symbol rate.
+         * @param frequency of the mark or space symbol to test for correlation
+         * @param averagingPeriod is the number of correlation values to average each period
+         * @param correlationPeriod is the number of samples to correlate each period
+         */
+        public Correlator(double sampleRate, double frequency, int averagingPeriod, int correlationPeriod)
+        {
+            mAveragingBuffer = new FloatAveragingBuffer(averagingPeriod);
+
+            IOscillator referenceSignalGenerator = new Oscillator(frequency, sampleRate);
+            mReferenceSamples = referenceSignalGenerator.generateReal(correlationPeriod);
+
+            mDemodulatedSamples = new float[correlationPeriod];
+        }
+
+        /**
+         * Processes each sample in the incoming sample buffer against a generated reference sample set for one symbol
+         * period to derive a correlation value that is in-turn averaged over one symbol period.
+         *
+         * @param reusableFloatBuffer containing FM demodulated samples
+         * @return a reusable array of correlation values for each sample
+         */
+        public float[] process(ReusableFloatBuffer reusableFloatBuffer)
+        {
+            if(mCorrelationValues == null || mCorrelationValues.length != reusableFloatBuffer.getSampleCount())
+            {
+                mCorrelationValues = new float[reusableFloatBuffer.getSampleCount()];
+            }
+
+            float[] samples = reusableFloatBuffer.getSamples();
+
+            int y;
+
+            for(int x = 0; x < samples.length; x++)
+            {
+                //Note: we're using array copy and dot product structures that the JRE can promote to SIMD intrinsics
+                //when the host processor supports SIMD instructions
+                System.arraycopy(mDemodulatedSamples, 1, mDemodulatedSamples, 0, mDemodulatedSamples.length - 1);
+                mDemodulatedSamples[mDemodulatedSamples.length - 1] = samples[x];
+
+                mCorrelationAccumulator = 0.0f;
+
+                for(y = 0; y < mDemodulatedSamples.length; y++)
+                {
+                    mCorrelationAccumulator += mDemodulatedSamples[y] * mReferenceSamples[y];
+                }
+
+                //Add the absolute value of correlation accumulator value to the averaging buffer and store the current
+                //average as the correlation value for this sample.  We use absolute value because we don't care if the
+                //signal is out of phase with the reference samples
+                mCorrelationValues[x] = mAveragingBuffer.get(Math.abs(mCorrelationAccumulator));
+            }
+
+            return mCorrelationValues;
+        }
+    }
+}

src/main/java/io/github/dsheirer/dsp/afsk/AFSK1200DecoderInstrumented.java

@@ -0,0 +1,51 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.afsk;
+
+import io.github.dsheirer.sample.Broadcaster;
+import io.github.dsheirer.sample.Listener;
+
+public class AFSK1200DecoderInstrumented extends AFSK1200Decoder
+{
+    private Broadcaster<Boolean> mSymbolBroadcaster = new Broadcaster<>();
+
+    public AFSK1200DecoderInstrumented(boolean invertOutput)
+    {
+        super(new AFSKSampleBufferInstrumented(SAMPLES_PER_SYMBOL, TIMING_ERROR_GAIN),
+            new AFSKTimingErrorDetectorInstrumented(SAMPLES_PER_SYMBOL), Output.NORMAL);
+    }
+
+    public AFSKSampleBufferInstrumented getSampleBuffer()
+    {
+        return (AFSKSampleBufferInstrumented)mSampleBuffer;
+    }
+
+    public AFSKTimingErrorDetectorInstrumented getErrorDetector()
+    {
+        return (AFSKTimingErrorDetectorInstrumented)mTimingErrorDetector;
+    }
+
+    protected void dispatch(boolean symbol)
+    {
+        super.dispatch(symbol);
+        mSymbolBroadcaster.broadcast(symbol);
+    }
+
+    public void addListener(Listener<Boolean> listener)
+    {
+        mSymbolBroadcaster.addListener(listener);
+    }
+}

src/main/java/io/github/dsheirer/dsp/afsk/AFSKSampleBuffer.java

@@ -0,0 +1,121 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.afsk;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class AFSKSampleBuffer
+{
+    private final static Logger mLog = LoggerFactory.getLogger(AFSKSampleBuffer.class);
+
+    private final static float SYMBOL_SAMPLE_THRESHOLD = 1.0f;
+    protected boolean[] mDelayLine;
+    protected int mDelayLinePointer = 0;
+
+    private int mHalfIntegerSamplesPerSymbol;
+    private int mPositiveSampleDecisionCount;
+    protected int mTwiceSamplesPerSymbol;
+    protected int mSymbolStart;
+    protected int mSymbolEnd;
+    protected int mSamplesPerSymbol;
+    protected float mSymbolSamplingPoint;
+    protected float mSymbolTimingGain;
+
+    /**
+     * Buffer to store complex sample data and produce interpolated samples.
+     * @param samplesPerSymbol
+     */
+    public AFSKSampleBuffer(int samplesPerSymbol, float symbolTimingGain)
+    {
+        mSamplesPerSymbol = samplesPerSymbol;
+        mSymbolTimingGain = symbolTimingGain;
+
+        mHalfIntegerSamplesPerSymbol = samplesPerSymbol / 2;
+        mSymbolSamplingPoint = samplesPerSymbol;
+        mTwiceSamplesPerSymbol = 2 * samplesPerSymbol;
+        mDelayLine = new boolean[2 * mTwiceSamplesPerSymbol];
+    }
+
+    /**
+     * Stores the sample in the sample buffer to support making symbol decisions.
+     *
+     * Note: use the hasSymbol() method to determine if sufficient samples have been collected to make a symbol
+     * determination.
+     *
+     * @param sample to store in the sample buffer
+     */
+    public void receive(boolean sample)
+    {
+        mSymbolSamplingPoint--;
+
+        mDelayLine[mDelayLinePointer] = sample;
+        mDelayLine[mDelayLinePointer + mTwiceSamplesPerSymbol] = sample;
+
+        //Increment pointer and keep pointer in bounds
+        mDelayLinePointer++;
+        mDelayLinePointer = mDelayLinePointer % mTwiceSamplesPerSymbol;
+    }
+
+    /**
+     * Adjusts samples per symbol and symbol timing counters and increments the sample counter to collect another
+     * symbol.
+     *
+     * @param symbolTimingError from a symbol timing error detector
+     */
+    public void resetAndAdjust(float symbolTimingError)
+    {
+        mSymbolSamplingPoint += (mSamplesPerSymbol + (symbolTimingError * mSymbolTimingGain));
+    }
+
+    public void setTimingGain(float gain)
+    {
+        mSymbolTimingGain = gain;
+    }
+
+    /**
+     * Indicates if this buffer has accumulated enough samples to represent a full symbol
+     */
+    public boolean hasSymbol()
+    {
+        return mSymbolSamplingPoint < SYMBOL_SAMPLE_THRESHOLD;
+    }
+
+    /**
+     * Calculates the symbol as a majority decision where the number of positive/true samples are greater than half
+     * of the samples per symbol.  Symbol decision is based on the samples collected over the preceeding 1.0 to 2.0
+     * symbol periods.
+     *
+     * @return a true symbol if the majority of the samples were true or positive, otherwise a false symbol.
+     */
+    public boolean getSymbol()
+    {
+        mPositiveSampleDecisionCount = 0;
+
+        mSymbolStart = mDelayLinePointer;
+        mSymbolEnd = mDelayLinePointer + mSamplesPerSymbol - 1;
+
+        for(int x = mSymbolStart; x <= mSymbolEnd; x++)
+        {
+            if(mDelayLine[x])
+            {
+                mPositiveSampleDecisionCount++;
+            }
+        }
+
+        return mPositiveSampleDecisionCount > mHalfIntegerSamplesPerSymbol;
+    }
+}

src/main/java/io/github/dsheirer/dsp/afsk/AFSKSampleBufferInstrumented.java

@@ -0,0 +1,90 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.afsk;
+
+public class AFSKSampleBufferInstrumented extends AFSKSampleBuffer
+{
+    public boolean mLastSymbol;
+
+    /**
+     * Buffer to store complex sample data and produce interpolated samples.
+     *
+     * @param samplesPerSymbol
+     * @param symbolTimingGain
+     */
+    public AFSKSampleBufferInstrumented(int samplesPerSymbol, float symbolTimingGain)
+    {
+        super(samplesPerSymbol, symbolTimingGain);
+    }
+
+    /**
+     * Sample delay buffer containing boolean (ie positive or negative) samples.
+     */
+    public boolean[] getDelayLine()
+    {
+        return mDelayLine;
+    }
+
+    /**
+     * Current delay buffer pointer which points to where the next sample will be stored and/or the oldest sample in
+     * the buffer.
+     */
+    public int getDelayLinePointer()
+    {
+        return mDelayLinePointer;
+    }
+
+    public int getDelayLineSecondPointer()
+    {
+        return mDelayLinePointer + mTwiceSamplesPerSymbol;
+    }
+
+    /**
+     * Current symbol timing gain value
+     * @return
+     */
+    public float getSymbolTimingGain()
+    {
+        return mSymbolTimingGain;
+    }
+
+    public float getSamplesPerSymbol()
+    {
+        return mSamplesPerSymbol;
+    }
+
+    @Override
+    public boolean getSymbol()
+    {
+        mLastSymbol = super.getSymbol();
+        return mLastSymbol;
+    }
+
+    public boolean getLastSymbol()
+    {
+        return mLastSymbol;
+    }
+
+    public int getSymbolStart()
+    {
+        return mSymbolStart;
+    }
+
+    public int getSymbolEnd()
+    {
+        return mSymbolEnd;
+    }
+}

src/main/java/io/github/dsheirer/dsp/afsk/AFSKTest.java

@@ -0,0 +1,122 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.afsk;
+
+import io.github.dsheirer.buffer.FloatAveragingBuffer;
+import io.github.dsheirer.dsp.mixer.IOscillator;
+import io.github.dsheirer.dsp.mixer.Oscillator;
+import io.github.dsheirer.sample.complex.Complex;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.text.DecimalFormat;
+
+public class AFSKTest
+{
+    private final static Logger mLog = LoggerFactory.getLogger(AFSK1200Decoder.class);
+
+    private static final DecimalFormat df = new DecimalFormat("00.000");
+
+    public static String format(double value)
+    {
+        if(value > 0)
+        {
+            return " " + df.format(value);
+        }
+        else
+        {
+            return df.format(value);
+        }
+    }
+
+    public static float[] generateAFSK1200(boolean[] symbols, int samplesPerSymbol, float gain)
+    {
+        float[] samples = new float[symbols.length * samplesPerSymbol];
+
+        Oscillator oscillator = new Oscillator(1200.0, (double)samplesPerSymbol * 1200);
+
+        for(int x = 0; x < symbols.length; x++)
+        {
+            oscillator.setFrequency(symbols[x] ? 1200.0 : 1800.0);
+
+            for(int y = 0; y < samplesPerSymbol; y++)
+            {
+                Complex sample = new Complex(oscillator.inphase(), oscillator.quadrature());
+                sample.multiply(gain);
+                samples[x * samplesPerSymbol + y] = sample.inphase();
+                oscillator.rotate();
+            }
+        }
+
+        return samples;
+    }
+
+    public static void main(String[] args)
+    {
+        int sampleSize = 6;
+
+        FloatAveragingBuffer avg1200 = new FloatAveragingBuffer(sampleSize);
+        FloatAveragingBuffer avg1800 = new FloatAveragingBuffer(sampleSize);
+
+        IOscillator oscillator1200 = new Oscillator(1200.0, 7200.0);
+        IOscillator oscillator1800 = new Oscillator(1800.0, 7200.0);
+        oscillator1200.generateReal(1);
+        oscillator1800.generateReal(1);
+
+        float[] reference1200 = oscillator1200.generateReal(sampleSize);
+        float[] reference1800 = oscillator1800.generateReal(sampleSize);
+
+        boolean[] symbols = new boolean[]{true,false,true,false,true,false,true,false,true,true,true,false,true,false,
+            false,false,true,false,false,false,false,true,false,true,true,true,true,false,true,true,false,true,false,
+            true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,
+            false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,
+            true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,
+            false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,
+            true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,
+            false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,
+            true,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,
+            false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false};
+
+        float[] samples = generateAFSK1200(symbols, 6, 0.5f);
+
+        mLog.debug("Length:" + samples.length);
+
+        int offset = 0;
+
+        float correlation1200 = 0.0f;
+        float correlation1800 = 0.0f;
+
+        while(offset + sampleSize < samples.length)
+        {
+            correlation1200 = 0.0f;
+            correlation1800 = 0.0f;
+
+            for(int x = 0; x < sampleSize; x++)
+            {
+                correlation1200 += reference1200[x] * samples[x + offset];
+                correlation1800 += reference1800[x] * samples[x + offset];
+            }
+
+            correlation1200 = avg1200.get(Math.abs(correlation1200));
+            correlation1800 = avg1800.get(Math.abs(correlation1800));
+
+            mLog.debug(offset + " 1200:" + format(correlation1200) + " 1800:" + format(correlation1800) +
+            " Decision: " + (correlation1200 > correlation1800 ? "0" : "1"));
+
+            offset++;
+        }
+    }
+}

src/main/java/io/github/dsheirer/dsp/afsk/AFSKTimingErrorDetector.java

@@ -0,0 +1,103 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.afsk;
+
+/**
+ * Zero crossing error detector.  Provides symbol timing error correction values by detecting zero-crossings within
+ * each symbol period.  Ideally there should be only 0 or 1 zero crossings within each symbol period.  However, when
+ * there is a slight DC offset in the demodulated samples, there can be up to 2 zero crossings within a symbol
+ * period.
+ *
+ * This detector will only provide error corrections when there are 1 or 2 zero crossings detected.  If the number
+ * of zero crossings is greater than 2, then it is assumed that there is no signal present and the returned timing
+ * error value is zero.  This detector provides an error correction value relative to (approximately) the middle of
+ * a symbol period and therefore continuously attempts to align zero crossings to the middle of the period.
+ *
+ * Since this detector does NOT use interpolation, the error signal will contain minor levels of symbol timing
+ * jitter.  Error signal values are reported as integrals of the sampling period.
+ */
+public class AFSKTimingErrorDetector
+{
+    protected boolean[] mBuffer;
+    protected int mDetectedZeroCrossing;
+    protected float mSymbolMiddle;
+    private int mZeroCrossingCount;
+
+    /**
+     * Constructs the detector for the specified samples per symbol.
+     *
+     * @param samplesPerSymbol
+     */
+    public AFSKTimingErrorDetector(int samplesPerSymbol)
+    {
+        mBuffer = new boolean[samplesPerSymbol];
+        mSymbolMiddle = (float)(samplesPerSymbol - 1) / 2.0f;
+    }
+
+    /**
+     * Stores the sample in the buffer.  Use the getError() method once enough samples have been processed to determine
+     * the error for a symbol period.
+     *
+     * @param sample
+     */
+    public void receive(boolean sample)
+    {
+        //Shift all samples left and store new sample at the end
+        System.arraycopy(mBuffer, 1, mBuffer, 0, mBuffer.length - 1);
+        mBuffer[mBuffer.length - 1] = sample;
+    }
+
+    /**
+     * Determines the symbol timing error for the samples processed thus far.  This method should be invoked once per
+     * symbol period, triggered via an external samples per symbol tracking process.
+     *
+     * @return symbol timing error calculated as the distance between the approximate symbol center and the next closest
+     * zero crossing index.  An error value of zero is returned if the number of zero crossings is less than one or
+     * greater than two.
+     */
+    public int getError()
+    {
+        mZeroCrossingCount = 0;
+
+        for(int x = 0; x < mBuffer.length - 1; x++)
+        {
+            if(mBuffer[x] ^ mBuffer[x + 1])
+            {
+                mDetectedZeroCrossing = x + 1;
+                mZeroCrossingCount++;
+
+                if(mZeroCrossingCount > 1)
+                {
+                    return 0; //Too many crossings
+                }
+            }
+        }
+
+        if(mZeroCrossingCount == 1)
+        {
+            if(mDetectedZeroCrossing > mSymbolMiddle)
+            {
+                return -(mBuffer.length - mDetectedZeroCrossing);
+            }
+            else
+            {
+                return mDetectedZeroCrossing + 1;
+            }
+        }
+
+        return 0;
+    }
+}

src/main/java/io/github/dsheirer/dsp/afsk/AFSKTimingErrorDetectorInstrumented.java

@@ -0,0 +1,53 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.afsk;
+
+import javafx.beans.property.SimpleIntegerProperty;
+
+public class AFSKTimingErrorDetectorInstrumented extends AFSKTimingErrorDetector
+{
+    public SimpleIntegerProperty timingError = new SimpleIntegerProperty();
+
+    /**
+     * Constructs the detector for the specified samples per symbol.
+     *
+     * @param samplesPerSymbol
+     */
+    public AFSKTimingErrorDetectorInstrumented(int samplesPerSymbol)
+    {
+        super(samplesPerSymbol);
+    }
+
+    @Override
+    public int getError()
+    {
+        int error = super.getError();
+
+        timingError.setValue(error);
+
+        return error;
+    }
+
+    public int getDetectedZeroCrossing()
+    {
+        return mDetectedZeroCrossing;
+    }
+
+    public boolean[] getBuffer()
+    {
+        return mBuffer;
+    }
+}

src/main/java/io/github/dsheirer/dsp/am/AMDemodulator.java

@@ -1,22 +1,82 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
 package io.github.dsheirer.dsp.am;
 
-public abstract class AMDemodulator
+import io.github.dsheirer.sample.buffer.ReusableBufferQueue;
+import io.github.dsheirer.sample.buffer.ReusableComplexBuffer;
+import io.github.dsheirer.sample.buffer.ReusableFloatBuffer;
+
+/**
+ * Performs AM demodulation on baseband I/Q samples to produce demodulated float output.
+ */
+public class AMDemodulator
 {
-	private float mGain;
-	
-	public AMDemodulator( float gain )
-	{
-		mGain = gain;
-	}
-	
-    public float demodulate( float inphase, float quadrature )
+    private ReusableBufferQueue mReusableBufferQueue = new ReusableBufferQueue("AMDemodulator");
+    private int mOutputBufferPointer;
+    private float mGain;
+
+    /**
+     * Constructs this demodulator where the specified gain is applied to demodulated output samples.
+     *
+     * @param gain to apply to demodulated output samples.
+     */
+    public AMDemodulator(float gain)
     {
-    	return (float)Math.sqrt( ( inphase * inphase ) + 
-    							 ( quadrature * quadrature ) ) * mGain; 
+        mGain = gain;
+    }
+
+    /**
+     * Sets the gain to the specified level.
+     */
+    public void setGain(float gain)
+    {
+        mGain = gain;
+    }
+
+    /**
+     * Demodulates the comples I/Q sample and returns the demodulated output sample.
+     *
+     * @param inphase sample
+     * @param quadrature sample
+     * @return AM demodulated sample
+     */
+    public float demodulate(float inphase, float quadrature)
+    {
+        return (float)Math.sqrt((inphase * inphase) + (quadrature * quadrature)) * mGain;
+    }
+
+    /**
+     * Demodulates the reusable comples sample buffer and returns a demodulated audio buffer.
+     * @param complexBuffer to demodulate
+     * @return demodulated audio buffer.
+     */
+    public ReusableFloatBuffer demodulate(ReusableComplexBuffer complexBuffer)
+    {
+        ReusableFloatBuffer reusableFloatBuffer = mReusableBufferQueue.getBuffer(complexBuffer.getSampleCount());
+        float[] input = complexBuffer.getSamples();
+        float[] output = reusableFloatBuffer.getSamples();
+        mOutputBufferPointer = 0;
+
+        for(int x= 0; x < complexBuffer.getSamples().length; x += 2)
+        {
+            output[mOutputBufferPointer++] = demodulate(input[x], input[x + 1]);
+        }
+
+        complexBuffer.decrementUserCount();
+
+        return reusableFloatBuffer;
     }
-    
-	public void setGain( float gain )
-	{
-		mGain = gain;
-	}
 }

src/main/java/io/github/dsheirer/dsp/am/AMDemodulator_CB.java

@@ -1,69 +0,0 @@
-/*******************************************************************************
- *     SDR Trunk 
- *     Copyright (C) 2014,2015 Dennis Sheirer
- * 
- *     This program is free software: you can redistribute it and/or modify
- *     it under the terms of the GNU General Public License as published by
- *     the Free Software Foundation, either version 3 of the License, or
- *     (at your option) any later version.
- * 
- *     This program is distributed in the hope that it will be useful,
- *     but WITHOUT ANY WARRANTY; without even the implied warranty of
- *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *     GNU General Public License for more details.
- * 
- *     You should have received a copy of the GNU General Public License
- *     along with this program.  If not, see <http://www.gnu.org/licenses/>
- ******************************************************************************/
-package io.github.dsheirer.dsp.am;
-
-import io.github.dsheirer.sample.Listener;
-import io.github.dsheirer.sample.complex.ComplexBuffer;
-import io.github.dsheirer.sample.real.RealBuffer;
-
-public class AMDemodulator_CB extends AMDemodulator implements Listener<ComplexBuffer>
-{
-	private Listener<RealBuffer> mListener;
-	
-	public AMDemodulator_CB( float gain )
-	{
-		super( gain );
-	}
-	
-	@Override
-	public void receive( ComplexBuffer buffer )
-	{
-		if( mListener != null )
-		{
-			float[] samples = buffer.getSamples();
-			
-			int half = samples.length / 2;
-			
-			float[] demodulated = new float[ half ];
-
-			for( int x = 0; x < half; x++ )
-			{
-				int index = x * 2;
-				
-				demodulated[ x ] = demodulate( samples[ index ], samples[ index + 1 ] );
-			}
-			
-			mListener.receive( new RealBuffer( demodulated ) );
-		}
-	}
-	
-	public void setListener( Listener<RealBuffer> listener )
-	{
-		mListener = listener;
-	}
-
-	public void removeListener()
-	{
-		mListener = null;
-	}
-
-	public void dispose()
-	{
-		mListener = null;
-	}
-}

src/main/java/io/github/dsheirer/dsp/filter/ComplexFilter.java

@@ -1,55 +0,0 @@
-/*******************************************************************************
- *     SDR Trunk 
- *     Copyright (C) 2014 Dennis Sheirer
- * 
- *     This program is free software: you can redistribute it and/or modify
- *     it under the terms of the GNU General Public License as published by
- *     the Free Software Foundation, either version 3 of the License, or
- *     (at your option) any later version.
- * 
- *     This program is distributed in the hope that it will be useful,
- *     but WITHOUT ANY WARRANTY; without even the implied warranty of
- *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *     GNU General Public License for more details.
- * 
- *     You should have received a copy of the GNU General Public License
- *     along with this program.  If not, see <http://www.gnu.org/licenses/>
- ******************************************************************************/
-package io.github.dsheirer.dsp.filter;
-
-import io.github.dsheirer.sample.Listener;
-import io.github.dsheirer.sample.complex.Complex;
-
-@Deprecated
-public abstract class ComplexFilter implements Listener<Complex>
-{
-	private Listener<Complex> mListener;
-	
-	public void setListener( Listener<Complex> listener )
-	{
-		mListener = listener;
-	}
-	
-	public void dispose()
-	{
-		mListener = null;
-	}
-	
-	public Listener<Complex> getListener()
-	{
-		return mListener;
-	}
-	
-	public boolean hasListener()
-	{
-		return mListener != null;
-	}
-	
-	protected void send( Complex sample )
-	{
-		if( mListener != null )
-		{
-			mListener.receive( sample );
-		}
-	}
-}

src/main/java/io/github/dsheirer/dsp/filter/FilterFactory.java

@@ -22,10 +22,10 @@
  ******************************************************************************/
 package io.github.dsheirer.dsp.filter;
 
-import io.github.dsheirer.dsp.filter.cic.ComplexPrimeCICDecimate;
 import io.github.dsheirer.dsp.filter.design.FilterDesignException;
 import io.github.dsheirer.dsp.filter.fir.FIRFilterSpecification;
 import io.github.dsheirer.dsp.filter.fir.remez.RemezFIRFilterDesigner;
+import io.github.dsheirer.dsp.filter.fir.remez.RemezFIRFilterDesignerWithLagrange;
 import org.jtransforms.fft.FloatFFT_1D;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -34,10 +34,14 @@ import java.util.Arrays;
 import java.util.Set;
 import java.util.TreeSet;
 
+/**
+ * Utility methods for designing various types of filters.
+ */
 public class FilterFactory
 {
-    private final static Logger mLog =
-        LoggerFactory.getLogger(FilterFactory.class);
+    private final static Logger mLog = LoggerFactory.getLogger(FilterFactory.class);
+    private static final double PERFECT_RECONSTRUCTION_GAIN_AT_BAND_EDGE = -6.020599842071533; //decibel(0.5, 0.0)
+    private static final double MARGIN_OF_ERROR = 0.0003;
 
     /**
      * Generates coefficients for a unity-gain, windowed low-pass filter
@@ -48,43 +52,49 @@ public class FilterFactory
      * @param window - to apply against the coefficients
      * @return
      */
-    public static float[] getSinc(int sampleRate,
-                                  long frequency,
-                                  int length,
-                                  Window.WindowType window)
+    public static float[] getSinc(double sampleRate, long frequency, int length, Window.WindowType window)
     {
-        //Ensure we have an odd length
-        assert (length % 2 == 0);
+        int evenLength = length % 2 == 0 ? length : length + 1;
 
         //Get unity response array (one element longer to align with IDFT size)
-        float[] frequencyResponse = getUnityResponseArray(sampleRate, frequency, length + 1);
+        float[] frequencyResponse = getUnityResponseArray(sampleRate, frequency, evenLength);
 
         //Apply Inverse DFT against frequency response unity values, leaving the
         //IDFT bin results in the frequency response array
-        FloatFFT_1D idft = new FloatFFT_1D(length + 1);
-        idft.realInverseFull(frequencyResponse, false);
+        FloatFFT_1D idft = new FloatFFT_1D(evenLength);
+        idft.realInverseFull(frequencyResponse, true);
 
         //Transfer the IDFT results to the return array
         float[] coefficients = new float[length];
-        int middleCoefficient = (int) (length / 2);
+        int middleCoefficient = (int)(length / 2);
 
-        //Bin 0 of the idft is our center coefficient
-        coefficients[middleCoefficient] = frequencyResponse[0];
-
-        //The remaining idft bins from 1 to (middle - 1) are the mirror image
-        //coefficients
-        for(int x = 1; x < middleCoefficient; x++)
+        if(length % 2 == 0) //Even length
         {
-            coefficients[middleCoefficient + x] = frequencyResponse[2 * x];
-            coefficients[middleCoefficient - x] = frequencyResponse[2 * x];
+            //The remaining idft bins from 1 to (middle - 1) are the mirror image
+            //coefficients
+            for(int x = 0; x < middleCoefficient; x++)
+            {
+                coefficients[middleCoefficient + x] = frequencyResponse[2 * x];
+                coefficients[middleCoefficient - x] = frequencyResponse[2 * x];
+            }
+        }
+        else
+        {
+            //Bin 0 of the idft is our center coefficient
+            coefficients[middleCoefficient] = frequencyResponse[0];
+
+            //The remaining idft bins from 1 to (middle - 1) are the mirror image
+            //coefficients
+            for(int x = 1; x < middleCoefficient; x++)
+            {
+                coefficients[middleCoefficient + x] = frequencyResponse[2 * x];
+                coefficients[middleCoefficient - x] = frequencyResponse[2 * x];
+            }
         }
 
         //Apply the window against the coefficients
         coefficients = Window.apply(window, coefficients);
 
-        //Normalize to unity (1) gain
-        coefficients = normalize(coefficients);
-
         return coefficients;
     }
 
@@ -95,7 +105,7 @@ public class FilterFactory
      * @param coefficients
      * @return
      */
-    private static float[] normalize(float[] coefficients)
+    public static float[] normalize(float[] coefficients)
     {
         float accumulator = 0;
 
@@ -112,6 +122,32 @@ public class FilterFactory
         return coefficients;
     }
 
+    /**
+     * Normalizes all filter coefficients to achieve an overall objective gain, by ensuring
+     * that the sum of the absolute value of all coefficients adds up to the objective.
+     *
+     * @param coefficients
+     * @return
+     */
+    public static float[] normalize(float[] coefficients, float objective)
+    {
+        float accumulator = 0;
+
+        for(int x = 0; x < coefficients.length; x++)
+        {
+            accumulator += Math.abs(coefficients[x]);
+        }
+
+        accumulator /= objective;
+
+        for(int x = 0; x < coefficients.length; x++)
+        {
+            coefficients[x] = coefficients[x] / accumulator;
+        }
+
+        return coefficients;
+    }
+
     /**
      * Constructs an array of unity (1) response values representing the
      * desired (pre-windowing) frequency response, used by the sync function
@@ -128,17 +164,15 @@ public class FilterFactory
      * @param length
      * @return
      */
-    public static float[] getUnityResponseArray(int sampleRate,
-                                                long frequency,
-                                                int length)
+    public static float[] getUnityResponseArray(double sampleRate, long frequency, int length)
     {
         float[] unityArray = new float[length * 2];
 
-        int binCount = (int) ((Math.round(
-            (float) frequency / (float) sampleRate * (float) length)));
 
         if(length % 2 == 0) //even length
         {
+            int binCount = (int)((Math.round((float)frequency / (float)sampleRate * (float)length)));
+
             for(int x = 0; x < binCount; x++)
             {
                 unityArray[x] = 1.0f;
@@ -147,9 +181,11 @@ public class FilterFactory
         }
         else //odd length
         {
+            int binCount = (int)((Math.round((float)frequency / (float)sampleRate * (float)length + 0.5)));
+
             unityArray[0] = 1.0f;
 
-            for(int x = 1; x <= binCount; x++)
+            for(int x = 1; x < binCount; x++)
             {
                 unityArray[x] = 1.0f;
                 unityArray[length - x] = 1.0f;
@@ -159,25 +195,6 @@ public class FilterFactory
         return unityArray;
     }
 
-    public static float[] getSine(float sampleRate, float frequency, int length)
-    {
-        float[] retVal = new float[length];
-
-        float radianFrequency = (float) (2.0d * Math.PI * (frequency / sampleRate));
-
-        int middle = (int) (length / 2);
-
-        for(int x = 0; x < middle; x++)
-        {
-            float val = (float) Math.sin(radianFrequency * x);
-
-            retVal[middle + x] = val;
-            retVal[middle - x] = -val;
-        }
-
-        return retVal;
-    }
-
     /**
      * Applies a repeating sequence of 1, -1 to the coefficients to invert
      * the frequency response of the filter.  Used in converting a low-pass
@@ -211,25 +228,9 @@ public class FilterFactory
      * @param windowType - window to apply against the generated coefficients
      * @return
      */
-    public static float[] getLowPass(int sampleRate,
-                                     long cutoff,
-                                     int filterLength,
-                                     Window.WindowType windowType)
+    public static float[] getLowPass(double sampleRate, long cutoff, int filterLength, Window.WindowType windowType)
     {
-        if(filterLength % 2 == 0) //even length
-        {
-            float[] values = getSinc(sampleRate, cutoff, filterLength + 2, windowType);
-
-            //throw away the 0 index and the last index
-            return Arrays.copyOfRange(values, 1, values.length - 2);
-        }
-        else
-        {
-            float[] values = getSinc(sampleRate, cutoff, filterLength + 1, windowType);
-
-            //throw away the 0 index
-            return Arrays.copyOfRange(values, 1, values.length);
-        }
+        return getSinc(sampleRate, cutoff, filterLength, windowType);
     }
 
     /**
@@ -246,26 +247,17 @@ public class FilterFactory
      * - passFrequency < stopFrequency
      * - stopFrequency <= sampleRate/2
      */
-    public static float[] getLowPass(int sampleRate,
-                                     int passFrequency,
-                                     int stopFrequency,
-                                     int attenuation,
-                                     Window.WindowType windowType,
-                                     boolean forceOddLength)
+    public static float[] getLowPass(double sampleRate, int passFrequency, int stopFrequency, int attenuation,
+                                     Window.WindowType windowType, boolean forceOddLength)
     {
         if(stopFrequency < passFrequency || stopFrequency > (sampleRate / 2))
         {
-            throw new IllegalArgumentException("FilterFactory - low pass "
-                + "filter pass frequency [" + passFrequency + "] must be "
-                + "less than the stop frequency [" + stopFrequency + "] "
-                + "and must be less than half [" + (int) (sampleRate / 2) +
-                "] of the sample rate [" + sampleRate + "]");
+            throw new IllegalArgumentException("FilterFactory - low pass filter pass frequency [" + passFrequency +
+                "] must be less than the stop frequency [" + stopFrequency + "] and must be less than half [" +
+                (int)(sampleRate / 2) + "] of the sample rate [" + sampleRate + "]");
         }
 
-        int tapCount = getTapCount(sampleRate,
-            passFrequency,
-            stopFrequency,
-            attenuation);
+        int tapCount = getTapCount(sampleRate, passFrequency, stopFrequency, attenuation);
 
         if(forceOddLength)
         {
@@ -289,34 +281,21 @@ public class FilterFactory
      * @param windowType - window to apply against the generated coefficients
      * @return
      */
-    public static float[] getHighPass(int sampleRate,
-                                      long cutoff,
-                                      int filterLength,
-                                      Window.WindowType windowType)
+    public static float[] getHighPass(int sampleRate, long cutoff, int filterLength, Window.WindowType windowType)
     {
         //Convert the high frequency cutoff to its low frequency cutoff
         //equivalent, so that when we generate the low pass filter, prior to
         //inversion, its at the correct frequency
         long convertedCutoff = sampleRate / 2 - cutoff;
 
-        return invert(getSinc(sampleRate,
-            convertedCutoff,
-            filterLength,
-            windowType));
+        return invert(getSinc(sampleRate, convertedCutoff, filterLength, windowType));
     }
 
-    public static float[] getHighPass(int sampleRate,
-                                      long stopFrequency,
-                                      long passFrequency,
-                                      int attenuation,
-                                      Window.WindowType windowType,
-                                      boolean forceOddLength)
+    public static float[] getHighPass(int sampleRate, long stopFrequency, long passFrequency, int attenuation,
+                                      Window.WindowType windowType, boolean forceOddLength)
     {
         /* reverse the stop and pass frequency to get the low pass variant */
-        int tapCount = getTapCount(sampleRate,
-            stopFrequency,
-            passFrequency,
-            attenuation);
+        int tapCount = getTapCount(sampleRate, stopFrequency, passFrequency, attenuation);
 
         if(forceOddLength)
         {
@@ -360,11 +339,10 @@ public class FilterFactory
     }
 
     /**
-     * Determines the number of fir filter taps required to produce the
-     * specified frequency response with passband ripple near .1dB.
+     * Determines the number of fir filter taps required to produce the specified frequency response with passband
+     * ripple near 0.1dB.
      *
-     * Implements the algorithm from Understanding Digital Signal Processing, 3e
-     * , Lyons, section 5.10.5.
+     * Implements the algorithm from Understanding Digital Signal Processing, 3e, Lyons, section 5.10.5.
      *
      * @param sampleRate in hertz
      * @param pass pass frequency in hertz
@@ -372,24 +350,11 @@ public class FilterFactory
      * @param attenuation in dB
      * @return
      */
-    public static int getTapCount(int sampleRate,
-                                  long pass,
-                                  long stop,
-                                  int attenuation)
+    public static int getTapCount(double sampleRate, long pass, long stop, int attenuation)
     {
-        double frequency = ((double) stop - (double) pass) / (double) sampleRate;
+        double frequency = ((double)stop - (double)pass) / sampleRate;
 
-        return (int) (Math.round((double) attenuation / (22.0d * frequency)));
-    }
-
-    public static ComplexPrimeCICDecimate getDecimationFilter(int sampleRate,
-                                                              int decimatedRate, int order, int passFrequency, int attenuation,
-                                                              Window.WindowType windowType)
-    {
-        int decimationRate = (int) (sampleRate / decimatedRate);
-
-        return new ComplexPrimeCICDecimate(decimationRate, order,
-            passFrequency, attenuation, windowType);
+        return (int)(Math.round((double)attenuation / (22.0d * frequency)));
     }
 
     /**
@@ -401,10 +366,7 @@ public class FilterFactory
      * polyphase filter decimation chain
      * @throws - AssertionException if sample rate is not a multiple of 48 kHz
      */
-    public static int[] getPolyphaseDecimationRates(int sampleRate,
-                                                    int decimatedRate,
-                                                    long passFrequency,
-                                                    long stopFrequency)
+    public static int[] getPolyphaseDecimationRates(int sampleRate, int decimatedRate, long passFrequency, long stopFrequency)
     {
         int[] rates;
 
@@ -414,7 +376,7 @@ public class FilterFactory
                 + "integer multiple of sample rate");
         }
 
-        int decimation = (int) (sampleRate / decimatedRate);
+        int decimation = (int)(sampleRate / decimatedRate);
 
         //Decimation rates below 20 will use single stage polyphase filter
         if(decimation < 20)
@@ -432,11 +394,6 @@ public class FilterFactory
 
             int stage1 = findClosest(optimalStage1, factors);
 
-//			mLog.info( "Decimation rate [" + decimation +
-//					  "] stage1 optimal [" + optimalStage1 +
-//					  "] stage1 actual [" + stage1 +
-//					  "]");
-
             if(stage1 == decimation || stage1 == 1)
             {
                 rates = new int[1];
@@ -447,7 +404,7 @@ public class FilterFactory
             {
                 rates = new int[2];
 
-                int stage2 = (int) (decimation / stage1);
+                int stage2 = (int)(decimation / stage1);
 
                 if(stage1 > stage2)
                 {
@@ -465,8 +422,7 @@ public class FilterFactory
     }
 
     /**
-     * Finds the factor that is closest to the desired factor, from an ordered
-     * list of factors.
+     * Finds the factor that is closest to the desired factor, from an ordered list of factors.
      */
     private static int findClosest(int desiredFactor, Set<Integer> factors)
     {
@@ -488,9 +444,8 @@ public class FilterFactory
     }
 
     /**
-     * Determines the factors that make up an integer.  Uses a brute force
-     * method to iterate all integers from 1 to value, determining which factors
-     * are evenly divisible into the value.
+     * Determines the factors that make up an integer.  Uses a brute force method to iterate all integers from 1 to
+     * value, determining which factors are evenly divisible into the value.
      *
      * @param value - integer decimation value
      * @return - ordered set of factors for value
@@ -498,11 +453,11 @@ public class FilterFactory
     private static Set<Integer> getFactors(int value)
     {
         Set<Integer> factors = new TreeSet<Integer>();
-		
-		/* Brute force */
+
+        /* Brute force */
         for(int x = 1; x <= value; x++)
         {
-            int remainder = (int) (value / x);
+            int remainder = (int)(value / x);
 
             if(remainder * x == value)
             {
@@ -514,14 +469,10 @@ public class FilterFactory
     }
 
     /**
-     * Determines the optimal decimation rate for stage 1 of a two-stage
-     * poly-phase decimation filter chain, to produce a final sample rate of
-     * 48 kHz using a pass bandwidth of 25 kHz.
+     * Determines the optimal decimation rate for stage 1 of a two-stage poly-phase decimation filter chain, to produce
+     * a final sample rate of 48 kHz using a pass bandwidth of 25 kHz.  Use for total decimation rates of 20 or higher.
      *
-     * Use for total decimation rates of 20 or higher.
-     *
-     * Implements the algorithm described in Lyons, Understanding Digital Signal
-     * Processing, 3e, section 10.2.1, page 511.
+     * Implements the algorithm described in Lyons, Understanding Digital Signal Processing, 3e, section 10.2.1, page 511.
      *
      * @param sampleRate
      * @param decimation
@@ -529,42 +480,29 @@ public class FilterFactory
      * @return optimum integer decimation rate for the first stage decimation
      * filter
      */
-    public static int getOptimalStageOneRate(int sampleRate,
-                                             int decimation,
-                                             long passFrequency,
-                                             long stopFrequency)
+    public static int getOptimalStageOneRate(int sampleRate, int decimation, long passFrequency, long stopFrequency)
     {
         double ratio = getBandwidthRatio(passFrequency, stopFrequency);
 
-        double numerator = 1.0d - (
-            Math.sqrt((double) decimation * ratio / (2.0d - ratio)));
+        double numerator = 1.0d - (Math.sqrt((double)decimation * ratio / (2.0d - ratio)));
 
         double denominator = 2.0d - (ratio * (decimation + 1.0d));
 
-        int retVal = (int) (2.0d * decimation * (numerator / denominator));
-
-//		mLog.info( "Optimal Stage 1 Decimation - rate [" + sampleRate +
-//				  "] pass [" + passFrequency +
-//				  "] bw ratio [" + ratio +
-//				  "] optimal [" + retVal +
-//				  "]" );
+        int retVal = (int)(2.0d * decimation * (numerator / denominator));
 
         return retVal;
     }
 
     /**
-     * Determines the F ratio as described in Lyons, Understanding Digital
-     * Signal Processing, 3e, section 10.2.1, page 511
-     *
-     * Used in conjunction with the optimal stage one decimation rate method
-     * above.
+     * Determines the F ratio as described in Lyons, Understanding Digital Signal Processing, 3e, section 10.2.1, page 511
+     * Used in conjunction with the optimal stage one decimation rate method above.
      */
     private static double getBandwidthRatio(long passFrequency, long stopFrequency)
     {
         assert (passFrequency < stopFrequency);
 
-        return ((double) (stopFrequency - passFrequency) /
-            (double) stopFrequency);
+        return ((double)(stopFrequency - passFrequency) /
+            (double)stopFrequency);
     }
 
     /**
@@ -575,15 +513,12 @@ public class FilterFactory
      * @param outputSampleRate
      * @return
      */
-    public static float[] getCICCleanupFilter(int outputSampleRate,
-                                              int passFrequency,
-                                              int attenuation,
-                                              Window.WindowType window)
+    public static float[] getCICCleanupFilter(int outputSampleRate, int passFrequency, int attenuation, Window.WindowType window)
     {
         int taps = getTapCount(outputSampleRate, passFrequency, passFrequency + 1500,
             attenuation);
-		
-		/* Make tap count odd */
+
+        /* Make tap count odd */
         if(taps % 2 == 0)
         {
             taps++;
@@ -599,7 +534,7 @@ public class FilterFactory
 
         //Transfer the IDFT results to the odd length return array
         float[] coefficients = new float[taps];
-        int middleCoefficient = (int) (taps / 2);
+        int middleCoefficient = (int)(taps / 2);
 
         //Bin 0 of the idft is our center coefficient
         coefficients[middleCoefficient] = frequencyResponse[0];
@@ -620,26 +555,22 @@ public class FilterFactory
         return coefficients;
     }
 
-    public static float[] getCICResponseArray(int sampleRate,
-                                              int frequency,
-                                              int length)
+    public static float[] getCICResponseArray(int sampleRate, int frequency, int length)
     {
         float[] cicArray = new float[length * 2];
 
-        int binCount = (int) ((Math.round(
-            (double) frequency / (double) sampleRate * 2.0d * (double) length)));
+        int binCount = (int)((Math.round(
+            (double)frequency / (double)sampleRate * 2.0d * (double)length)));
 
         cicArray[0] = 1.0f;
 
-        float unityResponse = (float) (Math.sin(1.0d / (double) length) /
-            (1.0d / (double) length));
+        float unityResponse = (float)(Math.sin(1.0d / (double)length) /
+            (1.0d / (double)length));
 
         for(int x = 1; x <= binCount; x++)
         {
-			/* Calculate unity response plus amplification for droop */
-            float compensated = 1.0f + (unityResponse -
-                (float) (Math.sin((double) x / (double) length) /
-                    ((double) x / (double) length)));
+            /* Calculate unity response plus amplification for droop */
+            float compensated = 1.0f + (unityResponse - (float)(Math.sin((double)x / (double)length) / ((double)x / (double)length)));
 
             cicArray[x] = compensated;
             cicArray[length - x] = compensated;
@@ -649,28 +580,29 @@ public class FilterFactory
     }
 
     /**
-     * Creates root raised cosine filter coefficients with a tap count equal
-     * to the symbols x samplesPerSymbol + 1.
+     * Creates root raised cosine filter coefficients with a tap count equal to the symbols x samplesPerSymbol + 1.
      *
      * Symbol count should be an even integer.
-     *
      * Ported to java from gnuradio/filter/firdes.cc
      *
-     * For 40db attenuation, calculate the number of symbols based on the
-     * following formula:
-     *
+     * For 40db attenuation, calculate the number of symbols based on the following formula:
      * Symbols = -44 * alpha + 33
      *
+     * Polyphase Channelizer notes:
+     * -Set samples Per Symbol at 2 (or more) * number of channels
+     * -Set symbolCount to sufficient size to produce required attenuation
+     * -Set symbol rate in hertz
+     * -Set alpha = (desired channel bandwidth / (symbol rate * samples per symbol) - 1.0
+     * -Channel bandwidth must be larger than symbol rate * samples per symbol, in order for there to be a positive alpha
+     *
      * @param samplesPerSymbol - number of samples per symbol
-     * @param symbols - number of symbols - must be even
-     * @param alpha - roll-off factor
+     * @param symbolCount - number of symbol intervals for the filter.  This directly impacts the filter size
+     * @param alpha - roll-off factor.
      * @return - filter coefficients
      */
-    public static float[] getRootRaisedCosine(float samplesPerSymbol,
-                                              int symbols,
-                                              float alpha)
+    public static float[] getRootRaisedCosine(int samplesPerSymbol, int symbolCount, float alpha)
     {
-        int taps = (int)(samplesPerSymbol * (float)symbols + 1.0f);
+        int taps = samplesPerSymbol * symbolCount;
 
         float scale = 0;
 
@@ -678,10 +610,10 @@ public class FilterFactory
 
         for(int x = 0; x < taps; x++)
         {
-            float index = (float) x - ((float) taps / 2.0f);
+            float index = (float)x - ((float)taps / 2.0f);
 
-            float x1 = (float) Math.PI * index / samplesPerSymbol;
-            float x2 = 4.0f * alpha * index / samplesPerSymbol;
+            float x1 = (float)Math.PI * index / (float)samplesPerSymbol;
+            float x2 = 4.0f * alpha * index / (float)samplesPerSymbol;
             float x3 = x2 * x2 - 1.0f;
 
             float numerator, denominator;
@@ -690,17 +622,15 @@ public class FilterFactory
             {
                 if(x != taps / 2)
                 {
-                    numerator = (float) Math.cos((1.0 + alpha) * x1) +
-                        (float) Math.sin((1.0f - alpha) * x1) /
-                            (4.0f * alpha * index / samplesPerSymbol);
+                    numerator = (float)Math.cos((1.0 + alpha) * x1) +
+                        (float)Math.sin((1.0f - alpha) * x1) / (4.0f * alpha * index / (float)samplesPerSymbol);
                 }
                 else
                 {
-                    numerator = (float) Math.cos((1.0f + alpha) * x1) +
-                        (1.0f - alpha) * (float) Math.PI / (4.0f * alpha);
+                    numerator = (float)Math.cos((1.0f + alpha) * x1) + (1.0f - alpha) * (float)Math.PI / (4.0f * alpha);
                 }
 
-                denominator = x3 * (float) Math.PI;
+                denominator = x3 * (float)Math.PI;
             }
             else
             {
@@ -713,14 +643,11 @@ public class FilterFactory
                 x3 = (1.0f - alpha) * x1;
                 x2 = (1.0f + alpha) * x1;
 
-                numerator = (float) (Math.sin(x2) * (1.0 + alpha) * Math.PI -
-                    Math.cos(x3) * ((1.0 - alpha) * Math.PI *
-                        (double) samplesPerSymbol) / (4.0 * alpha * index) +
-                    Math.sin(x3) * (double) samplesPerSymbol *
-                        (double) samplesPerSymbol / (4.0 * alpha * index * index));
+                numerator = (float)(Math.sin(x2) * (1.0f + alpha) * Math.PI - Math.cos(x3) * ((1.0 - alpha) * Math.PI *
+                    (double)samplesPerSymbol) / (4.0 * alpha * index) + Math.sin(x3) * (double)samplesPerSymbol *
+                    (double)samplesPerSymbol / (4.0 * alpha * index * index));
 
-                denominator = (float) (-32.0 * Math.PI * alpha * alpha * index /
-                    (double) samplesPerSymbol);
+                denominator = (float)(-32.0 * Math.PI * alpha * alpha * index / (double)samplesPerSymbol);
             }
 
             coefficients[x] = 4.0f * alpha * numerator / denominator;
@@ -740,10 +667,10 @@ public class FilterFactory
     }
 
     /**
-     * Creates a filter from the filter specification
+     * Creates a filter from the filter specification using the remez exchange design algorithm
      *
      * @param specification
-     * @return
+     * @return filter coefficients
      * @throws FilterDesignException if the filter cannot be designed
      */
     public static float[] getTaps(FIRFilterSpecification specification) throws FilterDesignException
@@ -757,4 +684,349 @@ public class FilterFactory
 
         return null;
     }
+
+    /**
+     * Evaluates the filter to determine the magnitude response (dB) at the specified frequency.
+     *
+     * @param filter to evaluate
+     * @param frequency to calculate (0 <> 0.5)
+     * @return magnitude frequency response in decibels
+     */
+    public static double evaluate(float[] filter, double frequency)
+    {
+        double real = 0.0;
+        double imag = 0.0;
+
+        for(int x = 0; x < filter.length; x++)
+        {
+            real += filter[x] * Math.cos(Math.PI * frequency * (double)x);
+            imag += filter[x] * Math.sin(Math.PI * frequency * (double)x);
+        }
+
+        return decibel(real, imag);
+    }
+
+    /**
+     * Calculates the decibel magnitude of the real and imaginary complex sample
+     *
+     * @param real (x-axis) value
+     * @param imag (y-axis) value
+     * @return magnitude in decibels
+     */
+    public static double decibel(double real, double imag)
+    {
+        return (float)(10.0 * Math.log10(Math.pow(real, 2.0) + Math.pow(imag, 2.0)));
+    }
+
+
+    public static float[] getRemezChannelizer(int channelBandwidth, int channels, int tapsPerChannel, double alpha,
+                                              double passRipple, double stopRipple) throws FilterDesignException
+    {
+        FIRFilterSpecification specification = FIRFilterSpecification.channelizerBuilder()
+            .sampleRate(channels * channelBandwidth * 4)
+            .channels(channels)
+            .channelBandwidth(channelBandwidth)
+            .tapsPerChannel(tapsPerChannel)
+            .alpha(alpha)
+            .passRipple(passRipple)
+            .stopRipple(stopRipple)
+            .build();
+
+        RemezFIRFilterDesignerWithLagrange designer = new RemezFIRFilterDesignerWithLagrange(specification);
+
+        float[] taps = designer.getImpulseResponse();
+
+        double bandEdgeFrequency = (double)channelBandwidth / (double)(channels * channelBandwidth * 2);
+
+        double response = decibel(designer.getFrequencyResponse(Math.cos(bandEdgeFrequency * Math.PI)), 0.0);
+        mLog.debug("Frequency Response at 1.0: " + response);
+        response = decibel(designer.getFrequencyResponse(Math.cos(bandEdgeFrequency * Math.PI * 2.0)), 0.0);
+        mLog.debug("Frequency Response at 2.0: " + response);
+
+        return taps;
+    }
+
+    /**
+     * Polyphase M2 synthesizer sync filter.  Designed for multiple M2 oversampled channel inputs and
+     * an M*channel count output.
+     *
+     * @param channelSampleRate per input channel
+     * @param channelBandwidth per input channel
+     * @param channels input count
+     * @param tapsPerChannel minumum.  This may be increased to meet the band edge -6.02dB requirement
+     * @return filter
+     * @throws FilterDesignException
+     */
+    public static float[] getSincM2Synthesizer(double channelSampleRate, double channelBandwidth, int channels,
+                                               int tapsPerChannel) throws FilterDesignException
+    {
+        int filterLength = (channels * tapsPerChannel) - 1;
+
+        double cutoff = (channelBandwidth * 1.10) / (channelSampleRate * (double)channels);
+
+        //Design the prototype synthesizer with 105% of the channel bandwidth produced by the channelizer.
+        float[] taps = FilterFactory.getKaiserSinc(filterLength, cutoff, 80.0);
+
+        //This is an odd length filter - increase the length by 1 by pre-padding a zero coefficient
+        float[] extendedTaps = new float[taps.length + 1];
+        System.arraycopy(taps, 0, extendedTaps, 1, taps.length);
+
+        return extendedTaps;
+    }
+
+    /**
+     * Creates a windowed-sync (Nyquist) M/2 prototype FIR filter for use with a Polyphase Channelizer/Synthesizer.
+     * The filter is designed for x2 oversampling of each channel and the filter cutoff frequency is incrementally
+     * adjusted to achieve a -6.02 dB attenuation at the channel band edge to enable perfect reconstruction of adjacent
+     * channels.
+     *
+     * The odd length sync filter that meets the design objectives will be increased in length by pre-padding a zero
+     * coefficient to produce a filter with a length that is an integral of the channel count.
+     *
+     * Note: the tapsPerChannel value will be iteratively increased (up to 10x) if a filter cannot be designed to meet
+     * the channel band edge attenuation objective.
+     *
+     * Note: a channelizer filter designed using a Blackman-Harris-7 window and 18-21 taps per channel creates a filter
+     * with attenuation in range of -60 to -80 dB at the edge of the 2x sampled channel.
+     *
+     * @param channelBandwidth - full bandwidth of the channel in hertz
+     * @param channels - number of channels
+     * @param tapsPerChannel - desired filter tap count per channel (may be increased to meet objective)
+     * @param windowType - to use when designing the windowed-sync filter
+     * @param logResults - to log a debug summary of the filter characteristics
+     *
+     * @return filter coefficients
+     *
+     * @throws FilterDesignException if a filter cannot be designed with a band edge attenuation of -6.02 dB
+     */
+
+    /**
+     * Polyphase M2 channelizer sync filter.  Designed for an M*channel input and an M2 channel output.
+     *
+     * @param channelBandwidth per channel
+     * @param channels count
+     * @param tapsPerChannel minimum.  This may be increased to meet the band edge -6.02dB requirement
+     * @param logResults to log the results of the design
+     * @return filter
+     * @throws FilterDesignException if the filter cannot be designed with a band edge of -6.02dB
+     */
+    public static float[] getSincM2Channelizer(double channelBandwidth, int channels, int tapsPerChannel,
+                                               boolean logResults) throws FilterDesignException
+    {
+        int currentTapsPerChannel = tapsPerChannel;
+        int filterLength = (channels * currentTapsPerChannel) - 1;
+
+        double sampleRate = channelBandwidth * channels;
+        double bandEdge = channelBandwidth / sampleRate;
+        double cutoffFrequency = bandEdge / 2.0;
+        double increment = cutoffFrequency * 0.1;
+
+        //Get an initial filter and band edge frequency response using the channel bandwidth as a cutoff
+        float[] taps = null;
+
+        taps = FilterFactory.getKaiserSinc(filterLength, cutoffFrequency, 80.0);
+        double response = FilterFactory.evaluate(taps, bandEdge);
+
+        //Set cutoff adjustment threshold - we'll test cutoff frequencies to around 1 hertz resolution
+        double incrementThreshold = 1.0 / sampleRate;
+
+        //Iteratively evaluate filters to find the filter with the highest cutoff frequency that meets the objective
+        while(increment > incrementThreshold)
+        {
+            //If the current cutoff meets the objective, test if a higher cutoff also meets the objective
+            if(matchesObjective(response, PERFECT_RECONSTRUCTION_GAIN_AT_BAND_EDGE, MARGIN_OF_ERROR) &&
+                (cutoffFrequency + increment <= bandEdge))
+            {
+                float[] higherCutoffTaps = FilterFactory.getKaiserSinc(filterLength, cutoffFrequency + increment, 80.0);
+                double higherCutoffResponse = FilterFactory.evaluate(higherCutoffTaps, bandEdge);
+
+                if(matchesObjective(higherCutoffResponse, PERFECT_RECONSTRUCTION_GAIN_AT_BAND_EDGE, MARGIN_OF_ERROR))
+                {
+                    cutoffFrequency += increment;
+                    taps = higherCutoffTaps;
+                    response = higherCutoffResponse;
+                }
+                else
+                {
+                    increment /= 2.0;
+                }
+            }
+            //If the current cutoff meets the objective, decrease the increment to test for smaller resolution cutoffs
+            else if(matchesObjective(response, PERFECT_RECONSTRUCTION_GAIN_AT_BAND_EDGE, MARGIN_OF_ERROR))
+            {
+                increment /= 2.0;
+            }
+            //Decrease the cutoff frequency - we can't meet the objective
+            else
+            {
+                cutoffFrequency -= increment;
+
+                if(cutoffFrequency <= 0)
+                {
+                    if(logResults)
+                    {
+                        mLog.debug("Warning: cannot design channelizer filter with tap count [" + currentTapsPerChannel +
+                            "] increasing tap count and starting over");
+                    }
+
+                    currentTapsPerChannel++;
+
+                    //After we've attempted increasing the taps per channel 10x, give up
+                    if(currentTapsPerChannel > (tapsPerChannel + 10))
+                    {
+                        throw new FilterDesignException("Couldn't design filter with taps per channel count in the " +
+                            "range of " + tapsPerChannel + " - " + (tapsPerChannel + 10) + " Sample Rate:" + sampleRate + " Channels:" + channels);
+                    }
+
+                    filterLength = channels * currentTapsPerChannel - 1;
+                    cutoffFrequency = channelBandwidth / sampleRate;
+                    increment = cutoffFrequency * 0.1;
+                }
+
+                taps = FilterFactory.getKaiserSinc(filterLength, cutoffFrequency, 80.0);
+                response = FilterFactory.evaluate(taps, bandEdge);
+            }
+        }
+
+        //This will probably never happen, but ...
+        if(!matchesObjective(response, PERFECT_RECONSTRUCTION_GAIN_AT_BAND_EDGE, MARGIN_OF_ERROR))
+        {
+            throw new FilterDesignException("Cannot design filter to specifications");
+        }
+
+        //This is an odd length filter - increase the length by 1 by pre-padding a zero coefficient
+        float[] extendedTaps = new float[taps.length + 1];
+        System.arraycopy(taps, 0, extendedTaps, 1, taps.length);
+
+        if(logResults)
+        {
+            mLog.debug("Polyphase Channelizer Filter Design Summary");
+            mLog.debug("-----------------------------------------------------");
+            mLog.debug("Input Sample Rate: " + sampleRate);
+            mLog.debug("Channel Bandwidth: " + channelBandwidth);
+            mLog.debug("Channels: " + channels);
+            mLog.debug("Window Type: " + Window.WindowType.KAISER.name());
+            mLog.debug("Taps Per Channel - Requested:" + tapsPerChannel + " Actual:" + ((double)extendedTaps.length / (double)channels));
+            mLog.debug("Filter Length: " + (extendedTaps.length));
+            mLog.debug("Requested Cutoff Frequency:  " + (sampleRate * bandEdge));
+            mLog.debug("Actual Cutoff Frequency:  " + (sampleRate * cutoffFrequency));
+            mLog.debug("Attenuation at 0.25 Channels:  " + evaluate(taps, bandEdge * 0.25) + "\tFrequency: " + (sampleRate * bandEdge * 0.25) + "  [" + (bandEdge * 0.25) + "]");
+            mLog.debug("Attenuation at 0.50 Channels:  " + evaluate(taps, bandEdge * 0.50) + "\tFrequency: " + (sampleRate * bandEdge * 0.50) + "  [" + (bandEdge * 0.50) + "]");
+            mLog.debug("Attenuation at 0.75 Channels:  " + evaluate(taps, bandEdge * 0.75) + "\tFrequency: " + (sampleRate * bandEdge * 0.75) + "  [" + (bandEdge * 0.75) + "]");
+            mLog.debug("Attenuation        OBJECTIVE:  " + PERFECT_RECONSTRUCTION_GAIN_AT_BAND_EDGE);
+            mLog.debug("Attenuation at 1.00 Channels:  " + evaluate(taps, bandEdge * 1.00) + "\tFrequency: " + (sampleRate * bandEdge * 1.0) + "  [" + (bandEdge * 1.0) + "]");
+            mLog.debug("Attenuation at 1.25 Channels:  " + evaluate(taps, bandEdge * 1.25) + "\tFrequency: " + (sampleRate * bandEdge * 1.25) + "  [" + (bandEdge * 1.25) + "]");
+            mLog.debug("Attenuation at 1.50 Channels:  " + evaluate(taps, bandEdge * 1.50) + "\tFrequency: " + (sampleRate * bandEdge * 1.5) + "  [" + (bandEdge * 1.5) + "]");
+            mLog.debug("Attenuation at 1.75 Channels:  " + evaluate(taps, bandEdge * 1.75) + "\tFrequency: " + (sampleRate * bandEdge * 1.75) + "  [" + (bandEdge * 1.75) + "]");
+            mLog.debug("Attenuation at 2.00 Channels:  " + evaluate(taps, bandEdge * 2.00) + "\tFrequency: " + (sampleRate * bandEdge * 2.0) + "  [" + (bandEdge * 2.0) + "]");
+        }
+
+        return extendedTaps;
+    }
+
+    /**
+     * Creates a windowed-sync (Nyquist) filter.
+     *
+     * @param cutoff frequency (0.0 <> 0.5)
+     * @param length of the filter - must be odd-length
+     * @param windowType to use in designing the filter
+     * @return filter coefficients.
+     * @throws FilterDesignException if the requested length is not odd
+     */
+    public static float[] getSinc(double cutoff, int length, Window.WindowType windowType) throws FilterDesignException
+    {
+        if(length % 2 == 0)
+        {
+            throw new FilterDesignException("Sinc filters must be odd-length");
+        }
+
+        float[] coefficients = new float[length];
+        int half = length / 2;
+
+        double[] window = Window.getWindow(windowType, length);
+
+        double scalor = 2.0 * cutoff;
+        double piScalor = Math.PI * scalor;
+
+        coefficients[half] = (float)(1.0 * scalor * window[half]);
+
+        for(int x = 1; x <= half; x++)
+        {
+            double a = piScalor * x;
+            double coefficient = scalor * Math.sin(a) / a;
+
+            coefficient *= window[half + x];
+            coefficients[half + x] = (float)coefficient;
+            coefficients[half - x] = (float)coefficient;
+        }
+
+        return coefficients;
+    }
+
+    /**
+     * Creates a Nyquist filter using a Kaiser Window.
+     *
+     * @param cutoff frequency (0.0 <> 0.5)
+     * @param length of the filter - must be odd-length
+     * @param attenuation desired for adjacent channels
+     * @return filter coefficients.
+     * @throws FilterDesignException if the requested length is not odd
+     */
+    public static float[] getKaiserSinc(int length, double cutoff, double attenuation) throws FilterDesignException
+    {
+        if(length % 2 == 0)
+        {
+            throw new FilterDesignException("Sinc filters must be odd-length");
+        }
+
+        float[] coefficients = new float[length];
+        int half = length / 2;
+
+        double[] window = Window.getKaiser(length, attenuation);
+
+        double scalor = 2.0 * cutoff;
+        double piScalor = Math.PI * scalor;
+
+        coefficients[half] = (float)(1.0 * scalor * window[half]);
+
+        for(int x = 1; x <= half; x++)
+        {
+            double a = piScalor * x;
+            double coefficient = scalor * Math.sin(a) / a;
+
+            coefficient *= window[half + x];
+            coefficients[half + x] = (float)coefficient;
+            coefficients[half - x] = (float)coefficient;
+        }
+
+        return coefficients;
+    }
+
+    /**
+     * Compares two doubles for equals and avoids any rounding error that are present.
+     *
+     * @param a value to compare
+     * @param objective value to compare
+     * @return true if they are equivalent within the margin of error
+     */
+    private static boolean matchesObjective(double a, double objective, double marginOfError)
+    {
+        return Math.abs(a - objective) <= marginOfError;
+    }
+
+    public static void main(String[] args)
+    {
+        float[] taps = null;
+
+        try
+        {
+            taps = FilterFactory.getSincM2Channelizer(12500.0, 800, 9, true);
+        }
+        catch(FilterDesignException fde)
+        {
+            mLog.error("Error", fde);
+        }
+
+        mLog.debug("Done: " + Arrays.toString(taps));
+    }
 }

src/main/java/io/github/dsheirer/dsp/filter/Filters.java

@@ -1719,7 +1719,32 @@ public enum Filters
 		 0.011873357051047719f, 0.0f, -0.007901319195893647f, 0.0f,
 		 0.005055504379767936f, 0.0f, -0.003054430179754289f, 0.0f,
 		 0.001695637278417295f, 0.0f, -0.000998606272947510f 
-	} );
+	}),
+
+	/**
+	 *         FIRFilterSpecification specification = FIRFilterSpecification.lowPassBuilder()
+	 *             .sampleRate(100)
+	 *             .gridDensity(16)
+	 *             .oddLength(true)
+	 *             .passBandCutoff(21)
+	 *             .passBandAmplitude(1.0)
+	 *             .passBandRipple(0.01)
+	 *             .stopBandStart(29)
+	 *             .stopBandAmplitude(0.0)
+	 *             .stopBandRipple(0.01) //Approximately -85 dB suppression
+	 *             .build();
+ 	 */
+	HALF_BAND_FILTER_27T(new float[]
+	{
+		 0.007495115f, 0.0f, -0.011045938f, 0.0f,
+		 0.019129561f, 0.0f, -0.031747308f, 0.0f,
+		 0.053220540f, 0.0f, -0.099569574f, 0.0f,
+		 0.316083550f, 0.5f,  0.316083550f, 0.0f,
+		-0.099569574f, 0.0f,  0.053220540f, 0.0f,
+		-0.031747308f, 0.0f,  0.019129561f, 0.0f,
+		-0.011045938f, 0.0f,  0.007495115f
+
+	});
 	
 	float[] mCoefficients;
 	

src/main/java/io/github/dsheirer/dsp/filter/Window.java

@@ -1,234 +1,523 @@
 /*******************************************************************************
- *     SDR Trunk 
- *     Copyright (C) 2014 Dennis Sheirer
- * 
- *     This program is free software: you can redistribute it and/or modify
- *     it under the terms of the GNU General Public License as published by
- *     the Free Software Foundation, either version 3 of the License, or
- *     (at your option) any later version.
- * 
- *     This program is distributed in the hope that it will be useful,
- *     but WITHOUT ANY WARRANTY; without even the implied warranty of
- *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *     GNU General Public License for more details.
- * 
- *     You should have received a copy of the GNU General Public License
- *     along with this program.  If not, see <http://www.gnu.org/licenses/>
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
  ******************************************************************************/
+
+/*
+ * Kaiser Window design methods: getKaiser(), getKaiserBeta() and getBesselZerothOrder() with minor naming changes were
+ * adopted from:
+ *
+ * https://github.com/rjeschke/neetutils-base/blob/master/src/main/java/com/github/rjeschke/neetutils/audio/FIRUtils.java
+ *
+ * Copyright (C) 2012 René Jeschke <rene_jeschke@yahoo.de>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
 package io.github.dsheirer.dsp.filter;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import java.util.Arrays;
 
 /**
- * Window creator
- * 
- * Blackman, Hamming and Hanning windows 
- * based on windowing methods described at:
- * http://www.mstarlabs.com/dsp/goertzel/goertzel.html
- * and
- * Understanding Digital Signal Processing 3e, Lyons, p.91
- * and 
- * Digital Filters for Everyone, Allred, p. 132
- * 
+ * Window factory and corresponding utility methods.
  */
 public class Window
 {
-    public static double[] getWindow( WindowType type, int length )
+    private final static Logger mLog = LoggerFactory.getLogger(Window.class);
+
+    private static final double TWO_PI = Math.PI * 2.0d;
+    private static final double FOUR_PI = Math.PI * 4.0d;
+    private static final double SIX_PI = Math.PI * 6.0d;
+    private static final double EIGHT_PI = Math.PI * 8.0d;
+
+    /**
+     * Creates a window of the specified type and length.
+     *
+     * @param type of window
+     * @param length of window
+     * @return window of the specified type and length
+     */
+    public static double[] getWindow(WindowType type, int length)
     {
-    	switch( type )
-    	{
-    		case BLACKMAN:
-    			return getBlackmanWindow( length );
-    		case COSINE:
-    			return getCosineWindow( length );
-    		case HAMMING:
-    			return getHammingWindow( length );
-    		case HANNING:
-    			return getHanningWindow( length );
-    		case NONE:
-			default:
-				return getRectangularWindow( length );
-    	}
+        switch(type)
+        {
+            case BLACKMAN:
+                return getBlackman(length);
+            case BLACKMAN_HARRIS_4:
+                return getBlackmanHarris4(length);
+            case BLACKMAN_HARRIS_7:
+                return getBlackmanHarris7(length);
+            case BLACKMAN_NUTALL:
+                return getBlackmanNutall(length);
+            case COSINE:
+                return getCosine(length);
+            case FLAT_TOP:
+                return getFlatTop(length);
+            case HAMMING:
+                return getHamming(length);
+            case HANN:
+                return getHann(length);
+            case KAISER:
+                throw new IllegalArgumentException("Kaiser Window cannot be created via this method.  Use the getKaiser() method instead.");
+            case NUTALL:
+                return getNutall(length);
+            case NONE:
+            default:
+                return getRectangular(length);
+        }
     }
 
-    public static double[] getRectangularWindow( int length )
+    /**
+     * Creates an all-pass or rectangular window.
+     *
+     * @param length of the window
+     * @return rectangular window
+     */
+    public static double[] getRectangular(int length)
     {
-    	double[] coefficients = new double[ length ];
+        double[] coefficients = new double[length];
 
-    	Arrays.fill( coefficients, 1.0d );
-    	
-    	return coefficients;
-    }
-    
-    public static double[] getCosineWindow( int length )
-    {
-    	double[] coefficients = new double[ length ];
+        Arrays.fill(coefficients, 1.0d);
 
-
-    	if( length % 2 == 0 ) //Even length
-    	{
-        	int half = (int)( ( length - 1 ) / 2 );
-
-        	for( int x = -half; x < length / 2 + 1; x++ )
-        	{
-    		    coefficients[ x + half ] = Math.cos( 
-    		    		( (double)x * Math.PI ) / ( (double)length + 1.0d ) );
-        	}
-    	}
-    	else //Odd length
-    	{
-        	int half = (int) length / 2;
-
-        	for( int x = -half; x < half + 1; x++ )
-        	{
-    		    coefficients[ x + half ] = Math.cos( 
-    		    		( (double)x * Math.PI ) / ( (double)length + 1.0d ) );
-        	}
-    	}
-
-    	return coefficients;
+        return coefficients;
     }
 
-    public static double[] getBlackmanWindow( int length )
+    /**
+     * Creates a cosine window of the specified length.
+     *
+     * @param length of the window
+     * @return cosine window
+     */
+    public static double[] getCosine(int length)
     {
-    	double[] coefficients = new double[ length ];
-    	
-    	for( int x = 0; x < length; x++ )
-    	{
-		    coefficients[ x ] = .426591D - 
-    	    	  ( .496561D * Math.cos( ( Math.PI * 2.0D * (double)x ) / (double)( length - 1 ) ) +
-    	    	  ( .076848D * Math.cos( ( Math.PI * 4.0D * (double)x ) / (double)( length - 1 ) ) ) );
-    	}
+        double[] coefficients = new double[length];
 
-    	return coefficients;
-    }
-    
-    public static double[] getHammingWindow( int length )
-    {
-    	double[] coefficients = new double[ length ];
-    	
-    	if( length % 2 == 0 ) //Even length
-    	{
-        	for( int x = 0; x < length; x++ )
-        	{
-    		    coefficients[ x ] = .54D - ( .46D * 
-		    		Math.cos( ( Math.PI * ( 2.0D * (double)x + 1.0d ) ) / (double)( length - 1 ) ) );
-        	}
-    	}
-    	else //Odd length
-    	{
-        	for( int x = 0; x < length; x++ )
-        	{
-    		    coefficients[ x ] = .54D - ( .46D * 
-    		    		Math.cos( ( 2.0D * Math.PI * (double)x ) / (double)( length - 1 ) ) );
-        	}
-    	}
+        if(length % 2 == 0) //Even length
+        {
+            int half = (int)((length - 1) / 2);
 
-    	return coefficients;
+            for(int x = -half; x < length / 2 + 1; x++)
+            {
+                coefficients[x + half] = Math.cos(
+                    ((double)x * Math.PI) / ((double)length + 1.0d));
+            }
+        }
+        else //Odd length
+        {
+            int half = (int)length / 2;
+
+            for(int x = -half; x < half + 1; x++)
+            {
+                coefficients[x + half] = Math.cos(
+                    ((double)x * Math.PI) / ((double)length + 1.0d));
+            }
+        }
+
+        return coefficients;
     }
 
-    public static double[] getHanningWindow( int length )
+    /**
+     * Creates a 3-term Blackman window.
+     *
+     * @param length of the window
+     * @return Blackman window
+     */
+    public static double[] getBlackman(int length)
     {
-    	double[] coefficients = new double[ length ];
+        double[] coefficients = new double[length];
 
-    	if( length % 2 == 0 ) //Even length
-    	{
-        	for( int x = 0; x < length; x++ )
-        	{
-    		    coefficients[ x ] = .5D - ( .5D * 
-    		    		Math.cos( ( Math.PI * ( 2.0D * (double)x + 1 ) ) / (double)( length - 1 ) ) );
-        	}
-    	}
-    	else //Odd length
-    	{
-        	for( int x = 0; x < length; x++ )
-        	{
-    		    coefficients[ x ] = .5D - ( .5D * 
-    		    		Math.cos( ( 2.0D * Math.PI * (double)x ) / (double)( length - 1 ) ) );
-        	}
-    	}
+        double denominator = length - 1;
+
+        double a0 = 0.426590713672;
+        double a1 = 0.496560619089;
+        double a2 = 0.0768486672399;
+
+        for(int x = 0; x < length; x++)
+        {
+            coefficients[x] = a0 -
+                (a1 * Math.cos((TWO_PI * (double)x) / denominator)) +
+                (a2 * Math.cos((FOUR_PI * (double)x) / denominator));
+        }
+
+        return coefficients;
+    }
+
+    /**
+     * Creates a 4-term Nutall window
+     *
+     * @param length of the window
+     * @return Nutall window
+     */
+    public static double[] getNutall(int length)
+    {
+        double[] coefficients = new double[length];
+
+        double denominator = length - 1;
+        double a0 = 0.355768;
+        double a1 = 0.487396;
+        double a2 = 0.144232;
+        double a3 = 0.012604;
+
+        for(int x = 0; x < length; x++)
+        {
+            coefficients[x] = a0 -
+                (a1 * Math.cos(TWO_PI * (double)x / denominator)) +
+                (a2 * Math.cos(FOUR_PI * (double)x / denominator)) -
+                (a3 * Math.cos(SIX_PI * (double)x / denominator));
+        }
+
+        return coefficients;
+    }
+
+    /**
+     * Creates a 4-term Blackman-Nutall window
+     *
+     * @param length of the window
+     * @return Blackman-Nutall window
+     */
+    public static double[] getBlackmanNutall(int length)
+    {
+        double[] coefficients = new double[length];
+
+        double denominator = length - 1;
+        double a0 = 0.3635819;
+        double a1 = 0.4891775;
+        double a2 = 0.1365995;
+        double a3 = 0.0106411;
+
+        for(int x = 0; x < length; x++)
+        {
+            coefficients[x] = a0 -
+                (a1 * Math.cos(TWO_PI * (double)x / denominator)) +
+                (a2 * Math.cos(FOUR_PI * (double)x / denominator)) -
+                (a3 * Math.cos(SIX_PI * (double)x / denominator));
+        }
+
+        return coefficients;
+    }
+
+    /**
+     * Creates a 4-term Blackman-Harris window
+     *
+     * @param length of the window
+     * @return Blackman-Harris window
+     */
+    public static double[] getBlackmanHarris4(int length)
+    {
+        double[] coefficients = new double[length];
+
+        double denominator = length - 1;
+        double a0 = 0.35875;
+        double a1 = 0.48829;
+        double a2 = 0.14128;
+        double a3 = 0.01168;
+
+        for(int x = 0; x < length; x++)
+        {
+            coefficients[x] = a0 -
+                (a1 * Math.cos(TWO_PI * (double)x / denominator)) +
+                (a2 * Math.cos(FOUR_PI * (double)x / denominator)) -
+                (a3 * Math.cos(SIX_PI * (double)x / denominator));
+        }
+
+        return coefficients;
+    }
+
+    /**
+     * Creates a 7-term Blackman-Harris window
+     *
+     * @param length of the window
+     * @return Blackman-Harris window
+     */
+    public static double[] getBlackmanHarris7(int length)
+    {
+        double[] coefficients = new double[length];
+
+        double denominator = length - 1;
+
+        double a0 = 0.27105140069342;
+        double a1 = 0.43329793923448;
+        double a2 = 0.21812299954311;
+        double a3 = 0.06592544638803;
+        double a4 = 0.01081174209837;
+        double a5 = 0.00077658482522;
+        double a6 = 0.00001388721735;
 
 
-    	return coefficients;
+        for(int x = 0; x < length; x++)
+        {
+            double w = TWO_PI * (double)x / denominator;
+
+            coefficients[x] = a0 -
+                (a1 * Math.cos(w)) +
+                (a2 * Math.cos(2.0 * w)) -
+                (a3 * Math.cos(3.0 * w)) +
+                (a4 * Math.cos(4.0 * w)) -
+                (a5 * Math.cos(5.0 * w)) +
+                (a6 * Math.cos(6.0 * w));
+        }
+
+        return coefficients;
+    }
+
+    /**
+     * Creates a Hamming window
+     *
+     * @param length of the window
+     * @return Hamming window
+     */
+    public static double[] getHamming(int length)
+    {
+        double[] coefficients = new double[length];
+
+        double a0 = 0.54;
+        double a1 = 0.46;
+        double denominator = length;
+
+        for(int x = 0; x < length; x++)
+        {
+            coefficients[x] = a0 - (a1 * Math.cos(TWO_PI * (double)x / denominator));
+        }
+
+        return coefficients;
+    }
+
+    /**
+     * Creates a Hann window
+     *
+     * @param length of the window
+     * @return Hann window
+     */
+    public static double[] getHann(int length)
+    {
+        double[] coefficients = new double[length];
+
+        double a0 = 0.5;
+        double a1 = 0.5;
+        double denominator = length;
+
+        for(int x = 0; x < length; x++)
+        {
+            coefficients[x] = a0 - (a1 * Math.cos(TWO_PI * (double)x / denominator));
+        }
+
+        return coefficients;
+    }
+
+    /**
+     * Creates a 4-term Blackman-Harris window
+     *
+     * @param length of the window
+     * @return Blackman-Harris window
+     */
+    public static double[] getFlatTop(int length)
+    {
+        double[] coefficients = new double[length];
+
+        double denominator = length - 1;
+
+        double a0 = 0.215578948;
+        double a1 = 0.41663158;
+        double a2 = 0.277263158;
+        double a3 = 0.083578947;
+        double a4 = 0.006947368;
+
+        for(int x = 0; x < length; x++)
+        {
+            coefficients[x] = a0 -
+                (a1 * Math.cos(TWO_PI * (double)x / denominator)) +
+                (a2 * Math.cos(FOUR_PI * (double)x / denominator)) -
+                (a3 * Math.cos(SIX_PI * (double)x / denominator)) +
+                (a4 * Math.cos(EIGHT_PI * (double)x / denominator));
+        }
+
+        return coefficients;
+    }
+
+    /**
+     * Calculates the beta (roll-off factor) for a Kaiser window based on the specified attenuation.
+     *
+     * @param attenuation in decibels
+     * @return beta value in the range of 0.0 to 1.0
+     */
+    public static double getKaiserBeta(double attenuation)
+    {
+        if(attenuation > 50.0)
+        {
+            return 0.1102 * (attenuation - 8.7);
+        }
+        else if(attenuation >= 21.0)
+        {
+            return (0.5842 * Math.pow(attenuation - 21.0, 0.4)) + (0.07886 * (attenuation - 21.0));
+        }
+        else
+        {
+            return 0.0;
+        }
+    }
+
+    /**
+     * Creates a Kaiser window.
+     *
+     * @param length of the window
+     * @param attenuation desired
+     * @return window
+     */
+    public static double[] getKaiser(int length, double attenuation)
+    {
+        double[] coefficients = new double[length];
+
+        double beta = getKaiserBeta(attenuation);
+
+        double betaBesselZerothOrder = getBesselZerothOrder(beta);
+
+        double temp;
+
+        for(int x = 0; x < coefficients.length; x++)
+        {
+            temp = beta * Math.sqrt(1.0 - Math.pow(2.0 * x / (length - 1) - 1.0, 2));
+            coefficients[x] = getBesselZerothOrder(temp) / betaBesselZerothOrder;
+        }
+
+        return coefficients;
+    }
+
+
+    /**
+     * Zeroth order modified Bessel function.
+     *
+     * @param x Value.
+     * @return Return value.
+     */
+    public final static double getBesselZerothOrder(final double x)
+    {
+        double f = 1;
+        final double x2 = x * x * 0.25;
+        double xc = x2;
+        double v = 1 + x2;
+        for (int i = 2; i < 100; i++)
+        {
+            f *= i;
+            xc *= x2;
+            final double a = xc / (f * f);
+            v += a;
+            if (a < 1e-20) break;
+        }
+
+        return v;
     }
 
     /**
      * Apply the window against an array of float-type samples
      */
-    public static float[] apply( double[] coefficients, float[] samples )
+    public static float[] apply(double[] coefficients, float[] samples)
     {
-		for( int x = 0; x < coefficients.length; x++ )
-		{
-		    samples[ x ] = (float)( samples[ x ] * coefficients[ x ] );
-		}
-		
-		return samples;
-    }
-    
-    public static float[] apply( WindowType type, float[] samples )
-    {
-    	double[] coefficients = getWindow( type, samples.length );
-    	
-    	return apply( coefficients, samples );
-    }
-    
-    /**
-     * Apply the window against an array of float-type samples
-     */
-    public static double[] apply( double[] coefficients, double[] samples )
-    {
-		for( int x = 0; x < coefficients.length; x++ )
-		{
-		    samples[ x ] = samples[ x ] * coefficients[ x ];
-		}
-		
-		return samples;
+        for(int x = 0; x < coefficients.length; x++)
+        {
+            samples[x] = (float)(samples[x] * coefficients[x]);
+        }
+
+        return samples;
     }
 
-    public static double[] apply( WindowType type, double[] samples )
+    /**
+     * Apply the window type against the float array of samples
+     *
+     * @param type of window to use
+     * @param samples to be windowed
+     * @return windowed samples
+     */
+    public static float[] apply(WindowType type, float[] samples)
     {
-    	double[] coefficients = getWindow( type, samples.length );
-    	
-    	return apply( coefficients, samples );
+        double[] coefficients = getWindow(type, samples.length);
+
+        return apply(coefficients, samples);
     }
-    
-    
-    
+
+    /**
+     * Apply the window against an array of double-type samples
+     */
+    public static double[] apply(double[] coefficients, double[] samples)
+    {
+        for(int x = 0; x < coefficients.length; x++)
+        {
+            samples[x] = samples[x] * coefficients[x];
+        }
+
+        return samples;
+    }
+
+    /**
+     * Apply the window type against the double array of samples
+     *
+     * @param type of window to use
+     * @param samples to be windowed
+     * @return windowed samples
+     */
+    public static double[] apply(WindowType type, double[] samples)
+    {
+        double[] coefficients = getWindow(type, samples.length);
+
+        return apply(coefficients, samples);
+    }
+
     /**
      * Window types
      */
     public enum WindowType
     {
-    	BLACKMAN, COSINE, HAMMING, HANNING, NONE;
-    }
-    
-	/**
-	 * Utility to log the double arrays
-	 */
-	public static String arrayToString( double[] array, boolean breaks )
-	{
-		StringBuilder sb = new StringBuilder();
-		for( int x = 0; x < array.length; x++ )
-		{
-			sb.append( x + ":" + array[ x ] );
+        BLACKMAN("Blackman"),
+        BLACKMAN_HARRIS_4("Blackman-Harris 4"),
+        BLACKMAN_HARRIS_7("Blackman-Harris 7"),
+        BLACKMAN_NUTALL("Blackman-Nutall"),
+        COSINE("Cosine"),
+        FLAT_TOP("Flat Top"),
+        HAMMING("Hamming"),
+        HANN("Hann"),
+        KAISER("Kaiser"),
+        NUTALL("Nutall"),
+        NONE("None");
 
-			if( breaks )
-			{
-				sb.append( "\n" );
-			}
-			else
-			{
-				if( x % 8 == 7 )
-				{
-					sb.append( "\n" );
-				}
-				else
-				{
-					sb.append( "\t" );
-				}
-			}
-		}
-		
-		return sb.toString();
-	}
+        private String mLabel;
+
+        WindowType(String label)
+        {
+            mLabel = label;
+        }
+
+        public String toString()
+        {
+            return mLabel;
+        }
+    }
+
+    public static void main(String[] args)
+    {
+        double[] kaiser = getKaiser(16, 80.0);
+
+        mLog.debug("Window:" + Arrays.toString(kaiser));
+    }
 }

src/main/java/io/github/dsheirer/dsp/filter/channelizer/AbstractComplexPolyphaseChannelizer.java

@@ -0,0 +1,170 @@
+/*******************************************************************************
+ * sdrtrunk
+ * Copyright (C) 2014-2017 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.filter.channelizer;
+
+import io.github.dsheirer.sample.Broadcaster;
+import io.github.dsheirer.sample.Listener;
+import io.github.dsheirer.sample.buffer.ReusableChannelResultsBuffer;
+import io.github.dsheirer.sample.buffer.ReusableChannelResultsBufferQueue;
+import io.github.dsheirer.sample.buffer.ReusableComplexBuffer;
+import io.github.dsheirer.source.ISourceEventListener;
+import io.github.dsheirer.source.SourceEvent;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.List;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+public abstract class AbstractComplexPolyphaseChannelizer implements Listener<ReusableComplexBuffer>, ISourceEventListener
+{
+    private final static Logger mLog = LoggerFactory.getLogger(AbstractComplexPolyphaseChannelizer.class);
+    private ReusableChannelResultsBufferQueue mBufferQueue = new ReusableChannelResultsBufferQueue("AbstractComplexPolyphaseChannelizer");
+    private Broadcaster<SourceEvent> mSourceChangeBroadcaster = new Broadcaster();
+    private List<PolyphaseChannelSource> mChannels = new CopyOnWriteArrayList<>();
+    private double mSampleRate;
+    private int mChannelCount;
+    private int mSubChannelCount;
+    private double mChannelSampleRate;
+
+    /**
+     * Complex sample polyphase channelizer
+     *
+     * @param channelCount
+     */
+    public AbstractComplexPolyphaseChannelizer(double sampleRate, int channelCount)
+    {
+        mChannelCount = channelCount;
+        mSubChannelCount = channelCount * 2; //Number of I/Q channels
+        mSampleRate = sampleRate;
+        mChannelSampleRate = (double)mSampleRate / (double)mChannelCount;
+    }
+
+    /**
+     * Input sample rate for this channelizer
+     * @return sample rate in hertz
+     */
+    public double getSampleRate()
+    {
+        return mSampleRate;
+    }
+
+    /**
+     * Sets the input sample rate for for this channelizer
+     * @param sampleRate in hertz
+     */
+    public void setRates(double sampleRate, int channelCount)
+    {
+        mSampleRate = sampleRate;
+        mChannelCount = channelCount;
+        mChannelSampleRate = mSampleRate / (double)mChannelCount;
+    }
+
+    /**
+     * Number of channels being processed by this channelizer.
+     */
+    public int getChannelCount()
+    {
+        return mChannelCount;
+    }
+
+    /**
+     * Number of sub channels (I/Q) being processed by this channelizer.  This is 2 * channel count.
+     */
+    public int getSubChannelCount()
+    {
+        return mSubChannelCount;
+    }
+
+    /**
+     * Output channel sample rate
+     * @return sample rate in hertz
+     */
+    public double getChannelSampleRate()
+    {
+        return mChannelSampleRate;
+    }
+
+    /**
+     * Dispatches the processed channel samples to any registered polyphase channel outputs.
+     *
+     * @param channelResultsBuffer containing an array of an array of I/Q samples per channel
+     */
+    protected void dispatch(ReusableChannelResultsBuffer channelResultsBuffer)
+    {
+        for(PolyphaseChannelSource channel : mChannels)
+        {
+            channelResultsBuffer.incrementUserCount();
+            channel.receiveChannelResults(channelResultsBuffer);
+        }
+
+        channelResultsBuffer.decrementUserCount();
+    }
+
+    /**
+     * Adds the polyphase channel source to receive processed output channel samples
+     *
+     * @param polyphaseChannelSource
+     */
+    public void addChannel(PolyphaseChannelSource polyphaseChannelSource)
+    {
+        if(polyphaseChannelSource != null && !mChannels.contains(polyphaseChannelSource))
+        {
+            mChannels.add(polyphaseChannelSource);
+            mSourceChangeBroadcaster.addListener(polyphaseChannelSource.getSourceEventListener());
+        }
+    }
+
+    /**
+     * Removes the polyphase channel source from receiving output channel samples.
+     *
+     * @param polyphaseChannelSource
+     */
+    public void removeChannel(PolyphaseChannelSource polyphaseChannelSource)
+    {
+        if(polyphaseChannelSource != null && mChannels.contains(polyphaseChannelSource))
+        {
+            mChannels.remove(polyphaseChannelSource);
+            mSourceChangeBroadcaster.removeListener(polyphaseChannelSource.getSourceEventListener());
+        }
+    }
+
+    /**
+     * Number of polyphase channels registered to receive sample streams
+     */
+    public int getRegisteredChannelCount()
+    {
+        return mChannels.size();
+    }
+
+    /**
+     * Creates or reuses a channel results buffer for subclass implementations to use for temporary
+     * storage of channel results through distribution and consumption of channel results by
+     * channel output processors.
+     */
+    protected ReusableChannelResultsBuffer getChannelResultsBuffer()
+    {
+        return mBufferQueue.getBuffer();
+    }
+
+    @Override
+    public Listener<SourceEvent> getSourceEventListener()
+    {
+        return mSourceChangeBroadcaster;
+    }
+}

src/main/java/io/github/dsheirer/dsp/filter/channelizer/ChannelCalculator.java

@@ -0,0 +1,557 @@
+/*******************************************************************************
+ * *********************************************************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2017 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ * *********************************************************************************************************************
+ ******************************************************************************/
+package io.github.dsheirer.dsp.filter.channelizer;
+
+import io.github.dsheirer.source.tuner.channel.TunerChannel;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class ChannelCalculator
+{
+    private final static Logger mLog = LoggerFactory.getLogger(ChannelCalculator.class);
+
+    /**
+     * Policy to determine desired corrective action for methods that calculate an index for a frequency or a frequency
+     * from an index where the frequency may exist either at the overlapping boundary of two indexes, or in the middle
+     * of the wrap-around (N/2) index.
+     */
+    public enum IndexBoundaryPolicy
+    {
+        ADJUST_POSITIVE,
+        ADJUST_NEGATIVE
+    }
+
+    private double mSampleRate;
+    private int mChannelCount;
+    private double mCenterFrequency;
+    private double mChannelBandwidth;
+    private double mOversampling = 2.0;
+
+    /**
+     * Calculates channel index(es) from a polyphase channelizer output to source a DDC polyphase channel source
+     * with a specified channel center frequency and bandwidth.
+     *
+     * Polyphase channel indexes are not linear/consecutive owing to the use of the FFT to rotate channels to their
+     * center frequencies following filtering in the polyphase filter bank.  As such, this calculator provides methods
+     * to determine the min/center/max frequency of each channel that is adjusted for the current center frequency
+     * value and to determine the channel index(es) that need to be targeted to produce a requested output channel
+     * with a specific frequency and bandwdith.
+     *
+     * @param sampleRate in hertz for the input sample rate from the sample source (ie tuner)
+     * @param channelCount number of channels in the polyphase filter bank
+     * @param centerFrequency center frequency for the input sample stream
+     * @param oversampling set to 1.0 for no oversample, or greater than 1.0 for oversampling
+     */
+    public ChannelCalculator(double sampleRate, int channelCount, double centerFrequency, double oversampling)
+    {
+        mSampleRate = sampleRate;
+        mChannelCount = channelCount;
+        mCenterFrequency = centerFrequency;
+        mOversampling = oversampling;
+
+        updateChannelBandwidth();;
+    }
+
+    /**
+     * Calculates the channel bandwidth from the sample rate and channel count.
+     */
+    private void updateChannelBandwidth()
+    {
+        mChannelBandwidth = (double)mSampleRate / (double)mChannelCount;
+    }
+
+    /**
+     * Center frequency for the channelizer
+     */
+    public double getCenterFrequency()
+    {
+        return mCenterFrequency;
+    }
+
+    /**
+     * Updates the center frequency for the channelizer
+     */
+    public void setCenterFrequency(double frequency)
+    {
+        mCenterFrequency = frequency;
+    }
+
+    /**
+     * Number of channels being channelized by the polyphase channelizer
+     */
+    public int getChannelCount()
+    {
+        return mChannelCount;
+    }
+
+    /**
+     * Updates the number of channels being channelized by the polyphase channelizer
+     */
+    public void setChannelCount(int channelCount)
+    {
+        mChannelCount = channelCount;
+        updateChannelBandwidth();
+    }
+
+    /**
+     * Identifies the index of the wrap-around channel meaning that the lower half of the channel exists at the upper
+     * end of the spectrum and the upper half of the channel exists at the lower end of the spectrum
+     *
+     * @return wrap-around channel index
+     */
+    public int getWrapAroundIndex()
+    {
+        return mChannelCount / 2;
+    }
+
+    /**
+     * PolyphaseChannelManager input sample rate
+     * @return input sample rate in hertz
+     */
+    public double getSampleRate()
+    {
+        return mSampleRate;
+    }
+
+    /**
+     * Updates the channel count using the sample rate argument to calculate the number of channels from the
+     * already established channel bandwidth.
+     *
+     * @param sampleRate to use for channel count
+     */
+    public void setRates(double sampleRate, int channelCount)
+    {
+        mSampleRate = sampleRate;
+        mChannelCount = channelCount;
+        updateChannelBandwidth();
+    }
+
+    /**
+     * Channel bandwidth.  Note: this value may be smaller than the channel sample rate when oversampling
+     * is being used.
+     */
+    public double getChannelBandwidth()
+    {
+        return mChannelBandwidth;
+    }
+
+    /**
+     * Half of the channel bandwidth.
+     */
+    public double getHalfChannelBandwidth()
+    {
+        return mChannelBandwidth / 2.0;
+    }
+
+    /**
+     * Oversampling rate produced by the channelizer.
+     *
+     * @return 1.0 for no oversampling, or a value greater than 1.0 when oversampling is applied.
+     */
+    public double getOversampling()
+    {
+        return mOversampling;
+    }
+
+    /**
+     * Sets the oversampling rate being applied by the polyphase channelizer
+     * @param oversampling rate where 1.0 indicates no oversampling, and a value greater than 1.0 indicates
+     * that the polyphase channelizer is oversampling each channel.
+     */
+    public void setOversampling(double oversampling)
+    {
+        mOversampling = oversampling;
+    }
+
+    /**
+     * Channel sample rate.  This value is the product of the filtered channel bandwidth times the
+     * oversampling rate.
+     */
+    public double getChannelSampleRate()
+    {
+        return getChannelBandwidth() * getOversampling();
+    }
+
+    /**
+     * PolyphaseChannelManager input minimum frequency
+     * @return minimum frequency in hertz
+     */
+    public long getMinimumFrequency()
+    {
+        return (long)(getCenterFrequency() - (getSampleRate() / 2.0));
+    }
+
+    /**
+     * PolyphaseChannelManager input maximum frequency
+     * @return maximum frequency in hertz
+     */
+    public long getMaximumFrequency()
+    {
+        return (long)(getCenterFrequency() + (getSampleRate() / 2.0));
+    }
+
+    /**
+     * Identifies the channelizer channel index(es) required to produce a tuner channel with the specified center
+     * frequency and channel bandwidth.
+     *
+     * @param tunerChannel specifying the desired channel frequency and bandwidth
+     *
+     * @return an array of one or more polyphase channelizer index(es) to target in order to produce an output channel
+     * for the desired frequency and bandwidth.
+     *
+     * @throws IllegalArgumentException if the tuner channel's minimum or maximum frequency is not contained
+     * within the channelizer's minimum or maximum frequency range
+     */
+    public List<Integer> getChannelIndexes(TunerChannel tunerChannel) throws IllegalArgumentException
+    {
+        if(tunerChannel.getMinFrequency() < getMinimumFrequency() ||
+           tunerChannel.getMaxFrequency() > getMaximumFrequency())
+        {
+            throw new IllegalArgumentException("Requested channel cannot be provided by this " +
+                "channelizer.  Requested channel [" + tunerChannel.getMinFrequency() + " - " +
+                tunerChannel.getMaxFrequency() + "] exceeds current channelizer frequency range [" +
+                getMinimumFrequency() + " - " + getMaximumFrequency() + "]");
+        }
+
+        int minIndex = getIndexForFrequency(tunerChannel.getMinFrequency(), IndexBoundaryPolicy.ADJUST_POSITIVE);
+        int maxIndex = getIndexForFrequency(tunerChannel.getMaxFrequency(), IndexBoundaryPolicy.ADJUST_NEGATIVE);
+
+        //Detect the unsourceable situation where the wrap around index would be included in both the minimum index
+        //and the maximum index, meaning that the tuner channel bandwidth is nearly the same as the input sample rate.
+        if(minIndex == getWrapAroundIndex() && maxIndex == getWrapAroundIndex())
+        {
+            throw new IllegalArgumentException("Requested tuner channel cannot be provided.  Requested bandwidth is " +
+                "within two channel bandwidths of the sample rate.");
+        }
+
+        List<Integer> indexes = new ArrayList<>();
+
+        indexes.add(minIndex);
+
+        if(minIndex != maxIndex)
+        {
+            //Ensure our min/max indexes are within the correct bounds 0 <> N-1 to safeguard the while loop below
+            if(minIndex < 0 || minIndex >= getChannelCount() || maxIndex < 0 || maxIndex >= getChannelCount())
+            {
+                throw new IllegalArgumentException("Something went wrong while calculating the min and max polyphase " +
+                    "channel indexes for tuner channel: " + tunerChannel);
+            }
+
+            int pointer = minIndex + 1;
+
+            if(pointer >= getChannelCount())
+            {
+                pointer -= getChannelCount();
+            }
+
+            while(pointer != maxIndex)
+            {
+                indexes.add(pointer);
+
+                pointer++;
+
+                if(pointer >= getChannelCount())
+                {
+                    pointer -= getChannelCount();
+                }
+            }
+
+            indexes.add(maxIndex);
+        }
+
+        return indexes;
+    }
+
+    /**
+     * Calculates the index for the specified frequency.  Certain frequencies can exist as both the maximum frequency
+     * of one channel and the minimum frequency of an adjacent channel.  The index boundary policy identifies your
+     * choice to select the higher frequency channel index (ADJUST_POSITIVE) or the lower frequency channel
+     * index (ADJUST_NEGATIVE).
+     *
+     * @param frequency to determine channel index for
+     * @param indexBoundaryPolicy to determine the behavior when the frequency overlaps two channel boundaries
+     * @return index for the frequency
+     */
+    public int getIndexForFrequency(long frequency, IndexBoundaryPolicy indexBoundaryPolicy)
+    {
+        double offset = frequency - getCenterFrequency();
+
+        if(Math.abs(offset) < getHalfChannelBandwidth())
+        {
+            return 0; //Center index
+        }
+
+        if(offset > 0)
+        {
+            offset += getHalfChannelBandwidth();
+        }
+        else
+        {
+            offset -= getHalfChannelBandwidth();
+        }
+
+        int indexOffset = (int)(offset / getChannelBandwidth());
+
+        if(indexOffset < 0)
+        {
+            indexOffset += getChannelCount();
+        }
+
+        if(indexBoundaryPolicy == IndexBoundaryPolicy.ADJUST_POSITIVE &&
+            isOverlapFrequency(frequency, indexOffset, indexOffset + 1))
+        {
+            indexOffset = normalize(indexOffset + 1);
+        }
+        else if(indexBoundaryPolicy == IndexBoundaryPolicy.ADJUST_NEGATIVE &&
+            isOverlapFrequency(frequency, indexOffset - 1, indexOffset))
+        {
+            indexOffset = normalize(indexOffset - 1);
+        }
+
+        return indexOffset;
+    }
+
+    /**
+     * Indicates if the frequency is an overlapping frequency between channel index 1 and channel index 2 where the
+     * maximum frequency of index 1 is the same as the minimum frequency of index 2 and both of these frequencies are
+     * the same as the frequency argument.
+     *
+     * Note: both index 1 and index 2 will be normalized to the range of 0 <> N-1 prior to determining overlap
+     *
+     * @param frequency to test for overlap between index 1 and 2
+     * @param index1 which is the lower channel index located next to index 2.
+     * @param index2 which is the higher channel index located next to index 1.
+     * @return true if frequency = index1 maximum frequency = index2 minimum frequency
+     */
+    public boolean isOverlapFrequency(long frequency, int index1, int index2)
+    {
+        index1 = normalize(index1);
+        index2 = normalize(index2);
+
+        //Check that these two indexes are side by side
+        int delta = normalize(index2 - index1);
+
+        if(delta != 1)
+        {
+            return false;
+        }
+
+        long index1MaximumFrequency = (long)getIndexMaximumFrequency(index1, IndexBoundaryPolicy.ADJUST_POSITIVE);
+        long index2MinimumFrequency = (long)getIndexMinimumFrequency(index2, IndexBoundaryPolicy.ADJUST_NEGATIVE);
+
+        if(index1 == getWrapAroundIndex())
+        {
+            index1MaximumFrequency = (long)getIndexMaximumFrequency(index1, IndexBoundaryPolicy.ADJUST_NEGATIVE);
+        }
+
+        if(index2 == getWrapAroundIndex())
+        {
+            index2MinimumFrequency = (long)getIndexMinimumFrequency(index2, IndexBoundaryPolicy.ADJUST_POSITIVE);
+        }
+
+        return frequency == index1MaximumFrequency && frequency == index2MinimumFrequency;
+    }
+
+    /**
+     * Normalizes the index to the range of 0 <> N-1 channel indexes</>
+     */
+    private int normalize(int index)
+    {
+        while(index < 0)
+        {
+            index += getChannelCount();
+        }
+
+        while(index >= getChannelCount())
+        {
+            index -= getChannelCount();
+        }
+
+        return index;
+    }
+
+    /**
+     * Calculates the center frequency for the channel identified by the index in the channel results array.
+     *
+     * @param index to determine the channel center frequency
+     * @return center frequency for the indexed channel
+     */
+    public double getIndexCenterFrequency(int index, IndexBoundaryPolicy indexBoundaryPolicy)
+    {
+        if(index < 0 || index >= getChannelCount())
+        {
+            throw new IllegalArgumentException("Illegal channel index [" + index + "] current max channels[" +
+                getChannelCount() + "]");
+        }
+
+        int wrapAroundIndex = getWrapAroundIndex();
+
+        if(index == wrapAroundIndex)
+        {
+            if(indexBoundaryPolicy == IndexBoundaryPolicy.ADJUST_POSITIVE)
+            {
+                return getCenterFrequency() + (index * getChannelBandwidth());
+            }
+            else
+            {
+                return getCenterFrequency() - (index * getChannelBandwidth());
+            }
+        }
+        else if(index < wrapAroundIndex)
+        {
+            return getCenterFrequency() + (index * getChannelBandwidth());
+        }
+        else
+        {
+            return getCenterFrequency() - ((getChannelCount() - index) * getChannelBandwidth());
+        }
+    }
+
+    /**
+     * Calculates the minimum frequency band edge for the channel identified by the index in the channel results
+     * array.
+     * @param index to calculate the minimum band edge frequency for the channel.
+     * @param indexBoundaryPolicy for the wrap around index to indicate if this method should return the minimum
+     * frequency of the upper spectrum half of the wrap around channel (ADJUST_POSITIVE) or the minimum frequency of the
+     * lower spectrum half of the wrap around channel (ADJUST_NEGATIVE)
+     * @return frequency of the minimum band edge
+     */
+    public double getIndexMinimumFrequency(int index, IndexBoundaryPolicy indexBoundaryPolicy)
+    {
+        if(index < 0 || index >= getChannelCount())
+        {
+            throw new IllegalArgumentException("Can't determine minimum frequency - illegal channel index [" +
+                index + "]");
+        }
+
+        int wrapAroundIndex = getWrapAroundIndex();
+
+        if(index == wrapAroundIndex)
+        {
+            if(indexBoundaryPolicy == IndexBoundaryPolicy.ADJUST_POSITIVE)
+            {
+                return getCenterFrequency() + ((double)index * getChannelBandwidth()) - getHalfChannelBandwidth();
+            }
+            else
+            {
+                return getIndexCenterFrequency(index, indexBoundaryPolicy);
+            }
+        }
+        else if(index <= wrapAroundIndex)
+        {
+            return getCenterFrequency() + ((double)index * getChannelBandwidth()) - getHalfChannelBandwidth();
+        }
+        else
+        {
+            return getCenterFrequency() - ((double)(getChannelCount() - index) * getChannelBandwidth()) -
+                getHalfChannelBandwidth();
+        }
+    }
+
+    /**
+     * Calculates the maximum frequency band edge for the channel identified by the index in the channel results
+     * array.
+     * @param index to calculate the maximum band edge frequency for the channel.
+     * @param indexBoundaryPolicy for the wrap around index to indicate if this method should return the maximum
+     * frequency of the upper spectrum half of the wrap around channel (ADJUST_POSITIVE) or the maximum frequency of the
+     * lower spectrum half of the wrap around channel (ADJUST_NEGATIVE)
+     * @return frequency of the maximum band edge
+     */
+    public double getIndexMaximumFrequency(int index, IndexBoundaryPolicy indexBoundaryPolicy)
+    {
+        if(index < 0 || index >= getChannelCount())
+        {
+            throw new IllegalArgumentException("Can't determine maximum frequency - illegal channel index [" +
+                index + "]");
+        }
+
+        int wrapAroundIndex = getWrapAroundIndex();
+
+        if(index == wrapAroundIndex)
+        {
+            if(indexBoundaryPolicy == IndexBoundaryPolicy.ADJUST_POSITIVE)
+            {
+                return getIndexCenterFrequency(index, indexBoundaryPolicy);
+            }
+            else
+            {
+                return getCenterFrequency() - ((double)index * getChannelBandwidth() - getHalfChannelBandwidth());
+            }
+        }
+        else if(index <= wrapAroundIndex)
+        {
+            return getCenterFrequency() + ((double)index * getChannelBandwidth()) + getHalfChannelBandwidth();
+        }
+        else
+        {
+            return getCenterFrequency() - ((double)(getChannelCount() - index) * getChannelBandwidth()) +
+                getHalfChannelBandwidth();
+        }
+    }
+
+    /**
+     * Calculates the center frequency for a channel that will be synthesized from the channel indexes.
+     * @param indexes that are contiguous in the spectrum
+     * @return center frequency in hertz
+     */
+    public long getCenterFrequencyForIndexes(List<Integer> indexes)
+    {
+        if(indexes.isEmpty())
+        {
+            throw new IllegalArgumentException("Indexes cannot be empty");
+        }
+
+        int centerIndex = (indexes.size() - 1) / 2;
+
+        int index = indexes.get(centerIndex);
+
+        if(indexes.size() % 2 == 0)
+        {
+            return (long)getIndexMaximumFrequency(index, IndexBoundaryPolicy.ADJUST_NEGATIVE);
+        }
+        else
+        {
+            if(index == getWrapAroundIndex())
+            {
+                return (long)getIndexCenterFrequency(index, IndexBoundaryPolicy.ADJUST_NEGATIVE);
+            }
+            else
+            {
+                return (long)getIndexCenterFrequency(index, IndexBoundaryPolicy.ADJUST_POSITIVE);
+            }
+        }
+    }
+
+    /**
+     * String representation of the channel calculator settings
+     */
+    public String toString()
+    {
+        StringBuilder sb = new StringBuilder();
+        sb.append("Channel Calculator Settings");
+        sb.append(" Channels:").append(getChannelCount());
+        sb.append(" Sample Rate:").append(getSampleRate());
+        sb.append(" Channel Bandwidth:").append(getChannelBandwidth());
+        sb.append(" Channel Rate:").append(getChannelSampleRate());
+        sb.append(" Min:").append(getMinimumFrequency());
+        sb.append(" Max:").append(getMaximumFrequency());
+        return sb.toString();
+    }
+}

src/main/java/io/github/dsheirer/dsp/filter/channelizer/ComplexPolyphaseChannelizerM2.java

@@ -0,0 +1,457 @@
+/*******************************************************************************
+ * sdrtrunk
+ * Copyright (C) 2014-2017 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.filter.channelizer;
+
+import io.github.dsheirer.dsp.filter.FilterFactory;
+import io.github.dsheirer.dsp.filter.design.FilterDesignException;
+import io.github.dsheirer.sample.IOverflowListener;
+import io.github.dsheirer.sample.Listener;
+import io.github.dsheirer.sample.buffer.ReusableChannelResultsBuffer;
+import io.github.dsheirer.sample.buffer.ReusableComplexBuffer;
+import org.jtransforms.fft.FloatFFT_1D;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.List;
+
+/**
+ * Non-Maximally Decimated Polyphase Filter Bank (NMDPFB) channelizer that divides the input baseband complex sample
+ * stream into equal bandwidth channels that are each oversampled by 2x for output.
+ *
+ * This polyphase channelizer is based off of the channelizer described by Fred Harris in Multirate Signal
+ * Processing for Communications Systems, p230-233.
+ *
+ * Samples are loaded into this filter one block at a time (1/2 channel count) and a filtered output is calculated
+ * to produce an overall 2x oversampled channel sample rate.  Each sample block load is preceded by a serpentine
+ * shift of the existing sample blocks.  We use the java System.arrayCopy() method which is able to leverage
+ * native processor intrinsics for efficiency.
+ *
+ * The prototype filter for the channelizer is rearranged to align with the structure of the sample buffer.
+ *
+ * Instead of using an array of channel filters as described in the Harris text, this filter and the sample buffer
+ * are arranged as a contiguous array to maximize Java's ability to leverage native processor Single Instruction
+ * Multiple Data (SIMD) intrinsics (since Java 8).  The filter process is broken into four steps:
+ *
+ *   -Multiply the inline array of samples and filter coefficients
+ *   -Accumulate the results for each sub-channel
+ *   -Rearrange the sub-channel results to correctly order the sub-channels
+ *   -Perform IFFT
+ *
+ * Note: design the prototype filter as a Nyquist windowed filter with a -6.02 db attenuation at the channel edge
+ * frequency if you need Perfect Reconstruction where you'll later re-join two or more channels to form a wider
+ * bandwidth channel or to isolate a signal that located between two channels.
+ */
+public class ComplexPolyphaseChannelizerM2 extends AbstractComplexPolyphaseChannelizer
+{
+    private final static Logger mLog = LoggerFactory.getLogger(ComplexPolyphaseChannelizerM2.class);
+
+    private static final int DEFAULT_MINIMUM_CHANNEL_BANDWIDTH = 12500;
+
+    //Sized at 152 buffers a second where max = 5 seconds and reset = 2 seconds worth of buffers
+    private IFFTProcessor mIFFTProcessor = new IFFTProcessor((5 * 152), (2 * 152));
+    private FloatFFT_1D mFFT;
+    private float[] mInlineSamples;
+    private float[] mInlineFilter;
+    private float[] mInlineInterimOutput;
+    private float[] mFilterAccumulator;
+    private boolean mTopBlockIndicator = true;
+    private int[] mTopBlockMap;
+    private int[] mMiddleBlockMap;
+    private int mSampleBufferPointer;
+    private int mSamplesPerBlock;
+    private int mTapsPerChannel;
+
+    /**
+     * Creates a NMDPFB channelizer instance.
+     *
+     * @param taps of a low-pass filter designed for the inbound sample rate with a cutoff frequency
+     * equal to the channel bandwidth (sample rate / filters).  If you need to synthesize (combine two or more
+     * channel outputs) a new bandwidth signal from the outputs of this filter, then the filter should be designed
+     * as a nyquist filter with -6 dB attenuation at the channel bandwidth cutoff frequency
+     * @param sampleRate of the incoming sample stream
+     * @param channelCount - number of filters/channels to output.  Since this filter bank performs 2x oversampling for
+     * each channel output, this number must be even (divisible by 2).
+     */
+    public ComplexPolyphaseChannelizerM2(float[] taps, int sampleRate, int channelCount)
+    {
+        super(sampleRate, channelCount);
+
+        if(channelCount % 2 != 0)
+        {
+            throw new IllegalArgumentException("Channel count must be an even multiple of the over-sample rate (2x)");
+        }
+
+        mTapsPerChannel = (int)Math.ceil((double)taps.length / (double)channelCount);
+
+        init(taps);
+    }
+
+    /**
+     * Creates a NMDPFB channelizer instance and designs a Perfect Reconstruction prototype filter appropriate for
+     * the baseband sample rate and quantity of filter taps per polyphase sub-channel.
+     *
+     * @param sampleRate to be channelized.
+     * @param tapsPerChannel to use when designing the filter
+     */
+    public ComplexPolyphaseChannelizerM2(double sampleRate, int tapsPerChannel) throws FilterDesignException
+    {
+        super(sampleRate, getChannelCount(sampleRate));
+
+        mTapsPerChannel = tapsPerChannel;
+
+        float[] filterTaps = FilterFactory.getSincM2Channelizer(getChannelSampleRate(), getChannelCount(),
+            mTapsPerChannel, false);
+
+        init(filterTaps);
+    }
+
+    /**
+     * Starts sample processing
+     */
+    public void start()
+    {
+        mIFFTProcessor.start();
+    }
+
+    /**
+     * Stops sample processing.
+     */
+    public void stop()
+    {
+        mIFFTProcessor.stop();
+    }
+
+    /**
+     * Calculates the multiple of two number of channels that can be channelized from the specified sample rate so that
+     * each channel has a minimum bandwidth of the default channel bandwidth (12.5 kHz).
+     * @param sampleRate to channelize
+     * @return number of multiple of two channels that can be channelized.
+     */
+    public static int getChannelCount(double sampleRate)
+    {
+        int channels = (int)(sampleRate / DEFAULT_MINIMUM_CHANNEL_BANDWIDTH);
+
+        if(channels % 2 != 0)
+        {
+            channels--;
+        }
+
+        mLog.debug("Sample Rate [" + sampleRate + "] providing [" + channels + "] channels at [" + (sampleRate / (double)channels) + "] Hz each");
+        return channels;
+    }
+
+    /**
+     * Updates this channelizer to use the new sample rate.  This method creates a new filter suitable for the
+     * sample rate and reinitializes all internal data structures to prepare for processing the new sample rate.
+     * @param sampleRate in hertz
+     */
+    @Override
+    public void setRates(double sampleRate, int channelCount)
+    {
+        try
+        {
+            super.setRates(sampleRate, channelCount);
+            float[] filterTaps = FilterFactory.getSincM2Channelizer(getChannelSampleRate(), getChannelCount(),
+                mTapsPerChannel, false);
+
+            init(filterTaps);
+        }
+        catch(FilterDesignException fde)
+        {
+            throw new IllegalArgumentException("Cannot create a channelizer filter for the specified sample rate [" +
+                sampleRate + "]");
+        }
+    }
+
+    /**
+     * Receives the complex sample buffer and processes the results through the channelizer.
+     */
+    @Override
+    public void receive(ReusableComplexBuffer reusableComplexBuffer)
+    {
+        ReusableChannelResultsBuffer channelResultsBuffer = getChannelResultsBuffer();
+        channelResultsBuffer.setTimestamp(reusableComplexBuffer.getTimestamp());
+
+        float[] samples = reusableComplexBuffer.getSamples();
+
+        int samplesPointer = 0;
+        int samplesToCopy;
+
+        while(samplesPointer < samples.length)
+        {
+            if(mSampleBufferPointer < mSamplesPerBlock)
+            {
+                samplesToCopy = mSamplesPerBlock - mSampleBufferPointer;
+
+                if((samples.length - samplesPointer) < samplesToCopy)
+                {
+                    samplesToCopy = (samples.length - samplesPointer);
+                }
+
+                System.arraycopy(samples, samplesPointer, mInlineSamples, mSampleBufferPointer, samplesToCopy);
+
+                mSampleBufferPointer += samplesToCopy;
+                samplesPointer += samplesToCopy;
+            }
+
+            if(mSampleBufferPointer >= mSamplesPerBlock)
+            {
+                //Filter buffered samples and produce a single sample across each of the polyphase channels
+                process(channelResultsBuffer);
+
+                //Right-shift the samples in the buffer over to make room for a new block of samples
+                //Note: since JDK 8, hotspot JIT compiler uses native processor intrinsics for efficiency
+                System.arraycopy(mInlineSamples, 0, mInlineSamples, mSamplesPerBlock, (mInlineSamples.length - mSamplesPerBlock));
+                mSampleBufferPointer = 0;
+            }
+        }
+
+        //Enqueue the channel results buffer for IFFT processing and distribution on a different thread
+        mIFFTProcessor.receive(channelResultsBuffer);
+
+        //Decrement the user count to let the originator know we're done with their buffer
+        reusableComplexBuffer.decrementUserCount();
+    }
+
+    /**
+     * Creates a top-block processing accumulator map that maps each interim filter and sample index product
+     * to the corresponding final output index for the array that will feed the IFFT.
+     *
+     * @param channelCount - number of channels
+     * @return output index to filter accumulator index mapping
+     */
+    private static int[] getTopBlockMap(int channelCount)
+    {
+        int[] newMap = new int[channelCount * 2];
+
+        //Reorder the subchannel arrays to the structure needed for top-block processing
+        int blockSize = channelCount / 2;
+
+        for(int channel = 0; channel < blockSize; channel++)
+        {
+            int newIndex = 2 * channel;
+            int originalIndex = 2 * (blockSize - channel - 1);
+            int offset = 2 * blockSize;
+
+            newMap[originalIndex] = newIndex;
+            newMap[originalIndex + 1] = newIndex + 1;
+            newMap[offset + originalIndex] = offset + newIndex;
+            newMap[offset + originalIndex + 1] = offset + newIndex + 1;
+        }
+
+        return newMap;
+    }
+
+    /**
+     * Creates a top-block processing accumulator map that maps each interim filter and sample index product
+     * to the corresponding final output index for the array that will feed the IFFT.
+     *
+     * @param channelCount - number of channels
+     * @return output index to filter accumulator index mapping
+     */
+    private static int[] getMiddleBlockMap(int channelCount)
+    {
+        int[] newMap = new int[channelCount * 2];
+
+        //Reorder the subchannel arrays to the structure needed for top-block processing
+        int blockSize = channelCount / 2;
+
+        for(int channel = 0; channel < blockSize; channel++)
+        {
+            int newIndex = 2 * channel;
+            int originalIndex = 2 * (blockSize - channel - 1);
+            int offset = 2 * blockSize;
+
+            newMap[offset + originalIndex] = newIndex;
+            newMap[offset + originalIndex + 1] = newIndex + 1;
+            newMap[originalIndex] = offset + newIndex;
+            newMap[originalIndex + 1] = offset + newIndex + 1;
+        }
+
+        return newMap;
+    }
+
+    /**
+     * Rearranges the filter coefficients to align with a contiguous sample buffer for processing efficiency.
+     * @param coefficients of the polyphase filter
+     * @param channelCount number of channels where each channel is an I/Q pair
+     * @return filter rearranged for inline sample buffer processing
+     */
+    private static float[] getAlignedFilter(float[] coefficients, int channelCount, int tapsPerChannel)
+    {
+        float[] filter = new float[channelCount * tapsPerChannel * 2];
+        int blockSize = channelCount;
+
+        int coefficientPointer = 0;
+        int filterPointer = 0;
+
+        //Create a new filter that duplicates each tap to produce an interleaved I/Q filter
+        while(coefficientPointer < coefficients.length)
+        {
+            filter[filterPointer++] = coefficients[coefficientPointer];
+            filter[filterPointer++] = coefficients[coefficientPointer++];
+        }
+
+        //Swap each of the coefficients on block size boundaries
+        for(int x = 0; x < filter.length; x += blockSize)
+        {
+            for(int y = 0; y < blockSize / 2; y++)
+            {
+                int index1 = x + y;
+                int index2 = x + (blockSize - y - 1);
+                float temp = filter[index2];
+                filter[index2] = filter[index1];
+                filter[index1] = temp;
+            }
+        }
+
+        return filter;
+    }
+
+
+    /**
+     * Processes the sample buffer for each new block of sample data that is loaded and distributes the results to any
+     * registered channel listeners.
+     */
+    private void process(ReusableChannelResultsBuffer channelResultsBuffer)
+    {
+        //Multiply each of the samples by the corresponding filter tap
+        for(int x = 0; x < mInlineSamples.length; x++)
+        {
+            mInlineInterimOutput[x] = mInlineSamples[x] * mInlineFilter[x];
+        }
+
+        Arrays.fill(mFilterAccumulator, 0.0f);
+
+        int tapOffset = 0;
+
+        //Accumulate the sample/filter product results into each of the I/Q sub-channels
+        for(int tap = 0; tap < mTapsPerChannel; tap++)
+        {
+            tapOffset = tap * getSubChannelCount();
+
+            for(int channel = 0; channel < getSubChannelCount(); channel++)
+            {
+                mFilterAccumulator[channel] += mInlineInterimOutput[tapOffset + channel];
+            }
+        }
+
+        float[] processed = channelResultsBuffer.getEmptyBuffer(getSubChannelCount());
+
+        if(mTopBlockIndicator)
+        {
+            for(int x = 0; x < getSubChannelCount(); x++)
+            {
+                processed[x] = mFilterAccumulator[mTopBlockMap[x]];
+            }
+        }
+        else
+        {
+            for(int x = 0; x < getSubChannelCount(); x++)
+            {
+                processed[x] = mFilterAccumulator[mMiddleBlockMap[x]];
+            }
+        }
+
+        channelResultsBuffer.addChannelResults(processed);
+
+        mTopBlockIndicator = !mTopBlockIndicator;
+    }
+
+    /**
+     * Initializes the channelizer filter structures.
+     *
+     * @param coefficients of the prototype filter for this channelizer
+     */
+    private void init(float[] coefficients)
+    {
+        mFFT = new FloatFFT_1D(getChannelCount());
+        int channelCount = getChannelCount();
+        int bufferLength = getSubChannelCount() * mTapsPerChannel;
+        mSamplesPerBlock = getChannelCount(); //Same as subChannelCount / 2
+        mTopBlockMap = getTopBlockMap(channelCount);
+        mMiddleBlockMap = getMiddleBlockMap(channelCount);
+        mInlineFilter = getAlignedFilter(coefficients, channelCount, mTapsPerChannel);
+        mInlineSamples = new float[bufferLength];
+        mInlineInterimOutput = new float[bufferLength];
+        mFilterAccumulator = new float[getSubChannelCount()];
+    }
+
+    /**
+     * Separate threaded processor to receive and enqueue filtered channel results buffers, perform IFFT on each array
+     * as required to align the phase of each polyphase channel, and then dispatch the results to any registered
+     * sample consumer channels.
+     */
+    public class IFFTProcessor extends ContinuousBufferProcessor<ReusableChannelResultsBuffer>
+    {
+        public IFFTProcessor(int maximumSize, int resetThreshold)
+        {
+            super(maximumSize, resetThreshold);
+
+            //We create a listener interface to receive the buffers from the scheduled thread pool
+            //dispatcher thread that is part of this continuous buffer processor.  We perform an IFFT on each
+            //channel results array contained in each results buffer and then dispatch the buffer
+            //so that it can be distributed to each channel listener.
+            setListener(new Listener<List<ReusableChannelResultsBuffer>>()
+            {
+                @Override
+                public void receive(List<ReusableChannelResultsBuffer> buffers)
+                {
+                    for(ReusableChannelResultsBuffer buffer: buffers)
+                    {
+                        for(float[] channelResults: buffer.getChannelResults())
+                        {
+                            //Rotate each of the channels to the correct phase using the IFFT
+                            mFFT.complexInverse(channelResults, true);
+                        }
+
+                        dispatch(buffer);
+                    }
+                }
+            });
+
+            setOverflowListener(new IOverflowListener()
+            {
+                @Override
+                public void sourceOverflow(boolean overflow)
+                {
+                    mLog.debug("IFFTProcessor overflow changed - overflow:" + overflow);
+                }
+            });
+        }
+
+        /**
+         * Clears any buffers from the dispatch/processing queue.  Overrides the parent method so that we can set
+         * the user count to 0 to allow the buffer to be reclaimed.
+         */
+        protected Collection<ReusableChannelResultsBuffer> clearQueue()
+        {
+            Collection<ReusableChannelResultsBuffer> buffersToDispose = super.clearQueue();
+
+            for(ReusableChannelResultsBuffer buffer: buffersToDispose)
+            {
+                buffer.clearUserCount();
+            }
+
+            return buffersToDispose;
+        }
+    }
+}

src/main/java/io/github/dsheirer/dsp/filter/channelizer/ContinuousBufferProcessor.java

@@ -0,0 +1,208 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2017 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.filter.channelizer;
+
+import io.github.dsheirer.sample.IOverflowListener;
+import io.github.dsheirer.sample.Listener;
+import io.github.dsheirer.sample.OverflowableTransferQueue;
+import io.github.dsheirer.util.ThreadPool;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.concurrent.ScheduledFuture;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+public class ContinuousBufferProcessor<E> implements Listener<E>
+{
+    private final static Logger mLog = LoggerFactory.getLogger(ContinuousBufferProcessor.class);
+
+    private OverflowableTransferQueue<E> mQueue;
+    private Listener<List<E>> mListener;
+    private ScheduledFuture<?> mScheduledFuture;
+    private AtomicBoolean mRunning = new AtomicBoolean();
+
+    /**
+     * Scheduled Buffer Processor combines an internal overflowable buffer with a scheduled runnable processing task
+     * for periodically distributing internally queued elements to the registered listener.  This processor provides
+     * a convenient way to create a thread-safe buffer for receiving elements from one thread/runnable and then
+     * distributing those elements to a registered listener where distribution occurs on a separate scheduled thread
+     * pool runnable thread.  This allows the calling input thread to quickly return without incurring any subsequent
+     * processing workload.
+     *
+     * The internal queue is an overflowable queue implementation that allows a listener to be registered to receive
+     * notifications of overflow and reset state.  Queue sizing parameters are specified in the constructor.
+     *
+     * @param maximumSize of the internal queue (overflow happens when this is exceeded)
+     * @param resetThreshold of the internal queue (overflow reset happens once queue size falls below this threshold
+     */
+    public ContinuousBufferProcessor(int maximumSize, int resetThreshold)
+    {
+        this(new OverflowableTransferQueue<>(maximumSize, resetThreshold));
+    }
+
+    /**
+     * Scheduled Buffer Processor combines an internal overflowable buffer with a scheduled runnable processing task
+     * for periodically distributing internally queued elements to the registered listener.  This processor provides
+     * a convenient way to create a thread-safe buffer for receiving elements from one thread/runnable and then
+     * distributing those elements to a registered listener where distribution occurs on a separate scheduled thread
+     * pool runnable thread.  This allows the calling input thread to quickly return without incurring any subsequent
+     * processing workload.
+     *
+     * The internal queue is an overflowable queue implementation that allows a listener to be registered to receive
+     * notifications of overflow and reset state.  Queue sizing parameters are specified in the constructor.
+     *
+     * @param queue implmentation of an overflowable transfer queue
+     */
+    public ContinuousBufferProcessor(OverflowableTransferQueue<E> queue)
+    {
+        mQueue = queue;
+    }
+
+    /**
+     * Sets the listener to receive notifications of buffer overflow and/or reset.  Note: this method can also be
+     * invoked with a null argument to clear the previously registered overflow listener.
+     *
+     * @param listener to receive overflow/reset notifications.
+     */
+    public void setOverflowListener(IOverflowListener listener)
+    {
+        mQueue.setOverflowListener(listener);
+    }
+
+    /**
+     * Sets or changes the listener to receive buffers from this processor.
+     * @param listener to receive buffers
+     */
+    public void setListener(Listener<List<E>> listener)
+    {
+        mListener = listener;
+    }
+
+    /**
+     * Primary input method for adding buffers to this processor.  Note: incoming buffers will be ignored if this
+     * processor is in a stopped state.  You must invoke start() to allow incoming buffers and initiate buffer
+     * processing.
+     *
+     * @param e to enqueue for distribution to a registered listener
+     */
+    @Override
+    public void receive(E e)
+    {
+        mQueue.offer(e);
+    }
+
+    /**
+     * Starts this buffer processor and allows queuing of incoming buffers.
+     */
+    public void start()
+    {
+        if(mRunning.compareAndSet(false, true))
+        {
+            mScheduledFuture = ThreadPool.SCHEDULED.scheduleAtFixedRate(new Processor(), 0, 5, TimeUnit.MILLISECONDS);
+        }
+    }
+
+    /**
+     * Stops this buffer processor, stops queuing of incoming buffers and clears the internal buffer queue.
+     */
+    public void stop()
+    {
+        if(mRunning.compareAndSet(true, false))
+        {
+            if(mScheduledFuture != null)
+            {
+                mScheduledFuture.cancel(true);
+                mScheduledFuture = null;
+            }
+
+            clearQueue();
+        }
+    }
+
+    /**
+     * Stops this buffer processor,stops queuing of incoming buffers and flushes the internal buffer queue
+     * contents to the listener.
+     */
+    public void flushAndStop()
+    {
+        if(mRunning.compareAndSet(true, false))
+        {
+            if(mScheduledFuture != null)
+            {
+                mScheduledFuture.cancel(true);
+                mScheduledFuture = null;
+            }
+
+            process();
+        }
+    }
+
+    /**
+     * Distributes queued buffers to the listener
+     */
+    private void process()
+    {
+        List<E> buffers = new ArrayList<>();
+
+        try
+        {
+            mQueue.drainTo(buffers);
+
+            if(mListener != null)
+            {
+                mListener.receive(buffers);
+            }
+        }
+        catch(Throwable throwable)
+        {
+            mLog.error("Error while dispatching buffers to listener", throwable);
+        }
+    }
+
+    /**
+     * Clears any buffers from the queue
+     */
+    protected Collection<E> clearQueue()
+    {
+        Collection<E> clearedElements = new ArrayList<>();
+        mQueue.drainTo(clearedElements);
+        return clearedElements;
+    }
+
+    /**
+     * Indicates if this processor is currently running
+     */
+    public boolean isRunning()
+    {
+        return mRunning.get();
+    }
+
+    /**
+     * Processor to service the buffer queue and distribute the buffers to the registered listener
+     */
+    class Processor implements Runnable
+    {
+        @Override
+        public void run()
+        {
+            process();
+        }
+    }
+}

src/main/java/io/github/dsheirer/dsp/filter/channelizer/ContinuousReusableBufferProcessor.java

@@ -0,0 +1,41 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.filter.channelizer;
+
+import io.github.dsheirer.sample.buffer.AbstractReusableBuffer;
+import io.github.dsheirer.sample.buffer.OverflowableReusableBufferTransferQueue;
+
+public class ContinuousReusableBufferProcessor<T extends AbstractReusableBuffer> extends ContinuousBufferProcessor<T>
+{
+    /**
+     * Scheduled Reusable Buffer Processor combines an internal overflowable buffer with a scheduled runnable processing
+     * task for periodically distributing internally queued elements to the registered listener.  This processor
+     * provides a convenient way to create a thread-safe buffer for receiving elements from one thread/runnable and then
+     * distributing those elements to a registered listener where distribution occurs on a separate scheduled thread
+     * pool runnable thread.  This allows the calling input thread to quickly return without incurring any subsequent
+     * processing workload.
+     *
+     * The internal queue is an overflowable queue implementation that allows a listener to be registered to receive
+     * notifications of overflow and reset state.  Queue sizing parameters are specified in the constructor.
+     *
+     * @param maximumSize of the internal queue (overflow happens when this is exceeded)
+     * @param resetThreshold of the internal queue (overflow reset happens once queue size falls below this threshold
+     */
+    public ContinuousReusableBufferProcessor(int maximumSize, int resetThreshold)
+    {
+        super(new OverflowableReusableBufferTransferQueue<T>(maximumSize, resetThreshold));
+    }
+}

src/main/java/io/github/dsheirer/dsp/filter/channelizer/PolyphaseChannelManager.java

@@ -0,0 +1,606 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.filter.channelizer;
+
+import io.github.dsheirer.dsp.filter.FilterFactory;
+import io.github.dsheirer.dsp.filter.channelizer.output.IPolyphaseChannelOutputProcessor;
+import io.github.dsheirer.dsp.filter.channelizer.output.OneChannelOutputProcessor;
+import io.github.dsheirer.dsp.filter.channelizer.output.TwoChannelOutputProcessor;
+import io.github.dsheirer.dsp.filter.design.FilterDesignException;
+import io.github.dsheirer.sample.Broadcaster;
+import io.github.dsheirer.sample.Listener;
+import io.github.dsheirer.sample.buffer.IReusableComplexBufferProvider;
+import io.github.dsheirer.sample.buffer.ReusableComplexBuffer;
+import io.github.dsheirer.source.ISourceEventProcessor;
+import io.github.dsheirer.source.Source;
+import io.github.dsheirer.source.SourceEvent;
+import io.github.dsheirer.source.SourceException;
+import io.github.dsheirer.source.tuner.TunerController;
+import io.github.dsheirer.source.tuner.channel.TunerChannel;
+import io.github.dsheirer.source.tuner.channel.TunerChannelSource;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Queue;
+import java.util.SortedSet;
+import java.util.TreeSet;
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+/**
+ * Polyphase Channel Manager is a DDC channel manager and complex buffer queue/processor for a tuner.  This class
+ * provides DDC polyphase channel sources and wraps a polyphase channelizer processing sample buffers produced by
+ * the tuner and distributing channelized sample buffers to each allocated DDC polyphase channel source.  This
+ * class is responsible for monitoring the tuner for changes in center frequency and/or sample rate and updating
+ * active DDC polyphase channel sources accordingly.  This class also monitors source event requests and
+ * notifications received from active DDC polyphase channel sources to adjust sample streams as required.
+ *
+ * Channel bandwidth and channel count are determined by the sample rate of the baseband buffer stream provider.  This
+ * class is currently designed to provide channels each with a minimum usable bandwidth of 12.5 kHz and oversampled by
+ * 2.0 to a minimum of 25.0 kHz channel sample rate.  If the baseband stream provider sample rate is not evenly
+ * divisible by 12.5 kHz channels for an even number of channels, the channel bandwidth will be increased.
+ *
+ * Note: add this channel manager as a source event listener to the complex buffer provider to ensure this manager
+ * adapts to changes in source frequency and sample rate.
+ */
+public class PolyphaseChannelManager implements ISourceEventProcessor
+{
+    private final static Logger mLog = LoggerFactory.getLogger(PolyphaseChannelManager.class);
+    private static final double MINIMUM_CHANNEL_BANDWIDTH = 12500.0;
+    private static final double CHANNEL_OVERSAMPLING = 2.0;
+    private static final int POLYPHASE_CHANNELIZER_TAPS_PER_CHANNEL = 9;
+    private static final int POLYPHASE_SYNTHESIZER_TAPS_PER_CHANNEL = 9;
+
+    private Broadcaster<SourceEvent> mSourceEventBroadcaster = new Broadcaster<>();
+    private IReusableComplexBufferProvider mReusableBufferProvider;
+    private List<PolyphaseChannelSource> mChannelSources = new CopyOnWriteArrayList<>();
+    private ChannelCalculator mChannelCalculator;
+    private ComplexPolyphaseChannelizerM2 mPolyphaseChannelizer;
+    private ChannelSourceEventListener mChannelSourceEventListener = new ChannelSourceEventListener();
+    private BufferSourceEventMonitor mBufferSourceEventMonitor = new BufferSourceEventMonitor();
+    private ContinuousBufferProcessor<ReusableComplexBuffer> mBufferProcessor;
+    private Map<Integer,float[]> mOutputProcessorFilters = new HashMap<>();
+
+    /**
+     * Creates a polyphase channel manager instance.
+     *
+     * @param reusableComplexBufferProvider (ie tuner) that supports register/deregister for reusable baseband sample buffer
+     * streams
+     * @param frequency of the baseband complex buffer sample stream (ie center frequency)
+     * @param sampleRate of the baseband complex buffer sample stream
+     */
+    public PolyphaseChannelManager(IReusableComplexBufferProvider reusableComplexBufferProvider,
+                                   long frequency, double sampleRate)
+    {
+        if(reusableComplexBufferProvider == null)
+        {
+            throw new IllegalArgumentException("Complex buffer provider argument cannot be null");
+        }
+
+        mReusableBufferProvider = reusableComplexBufferProvider;
+
+        int channelCount = (int)(sampleRate / MINIMUM_CHANNEL_BANDWIDTH);
+
+        //Ensure channel count is an even integer since we're using a 2x oversampling polyphase channelizer
+        if(channelCount % 2 != 0)
+        {
+            channelCount--;
+        }
+
+        mChannelCalculator = new ChannelCalculator(sampleRate, channelCount, frequency, CHANNEL_OVERSAMPLING);
+
+        mBufferProcessor = new ContinuousBufferProcessor(200, 50);
+        mBufferProcessor.setListener(mBufferSourceEventMonitor);
+    }
+
+    /**
+     * Creates a polyphase channel manager for the tuner controller
+     *
+     * @param tunerController for a tuner that provides a baseband complex buffer stream.
+     */
+    public PolyphaseChannelManager(TunerController tunerController)
+    {
+        this(tunerController, tunerController.getFrequency(), tunerController.getSampleRate());
+    }
+
+    /**
+     * Current channel sample rate which is (2 * channel bandwidth).
+     */
+    public double getChannelSampleRate()
+    {
+        return mChannelCalculator.getChannelSampleRate();
+    }
+
+    /**
+     * Current channel bandwidth/spacing.
+     */
+    public double getChannelBandwidth()
+    {
+        return mChannelCalculator.getChannelBandwidth();
+    }
+
+    /**
+     * Provides a Digital Drop Channel (DDC) for the specified tuner channel or returns null if the channel can't be
+     * sourced due to the current center frequency and/or sample rate.
+     * @param tunerChannel specifying center frequency and bandwidth.
+     * @return source or null.
+     */
+    public TunerChannelSource getChannel(TunerChannel tunerChannel)
+    {
+        PolyphaseChannelSource channelSource = null;
+
+        try
+        {
+            List<Integer> polyphaseIndexes = mChannelCalculator.getChannelIndexes(tunerChannel);
+
+            IPolyphaseChannelOutputProcessor outputProcessor = getOutputProcessor(polyphaseIndexes);
+
+            if(outputProcessor != null)
+            {
+                long centerFrequency = mChannelCalculator.getCenterFrequencyForIndexes(polyphaseIndexes);
+
+                channelSource = new PolyphaseChannelSource(tunerChannel, outputProcessor, mChannelSourceEventListener,
+                    mChannelCalculator.getChannelSampleRate(), centerFrequency);
+
+                mChannelSources.add(channelSource);
+            }
+        }
+        catch(IllegalArgumentException iae)
+        {
+            mLog.info("Can't provide DDC for " + tunerChannel.toString() + " due to channelizer frequency [" +
+                mChannelCalculator.getCenterFrequency() + "] and sample rate [" +
+                (mChannelCalculator.getChannelCount() * mChannelCalculator.getChannelBandwidth()) + "]");
+        }
+
+        return channelSource;
+    }
+
+    /**
+     * Creates a processor to process the channelizer channel indexes into a composite output stream providing
+     * channelized complex sample buffers to a registered source listener.
+     * @param indexes to target by the output processor
+     * @return output processor compatible with the number of indexes to monitor
+     */
+    private IPolyphaseChannelOutputProcessor getOutputProcessor(List<Integer> indexes)
+    {
+        switch(indexes.size())
+        {
+            case 1:
+                return new OneChannelOutputProcessor(mChannelCalculator.getChannelSampleRate(), indexes,
+                    mChannelCalculator.getChannelCount());
+            case 2:
+                try
+                {
+                    float[] filter = getOutputProcessorFilter(2);
+                    return new TwoChannelOutputProcessor(mChannelCalculator.getChannelSampleRate(), indexes, filter,
+                        mChannelCalculator.getChannelCount());
+                }
+                catch(FilterDesignException fde)
+                {
+                    mLog.error("Error designing 2 channel synthesis filter for output processor");
+                }
+            default:
+                //TODO: create output processor for greater than 2 input channels
+                mLog.error("Request to create an output processor for unexpected channel index size:" + indexes.size());
+                mLog.info(mChannelCalculator.toString());
+                return null;
+        }
+    }
+
+    /**
+     * Starts/adds the channel source to receive channelized sample buffers, registering with the tuner to receive
+     * sample buffers when this is the first channel.
+     *
+     * @param channelSource to start
+     */
+    private void startChannelSource(PolyphaseChannelSource channelSource)
+    {
+        synchronized(mBufferProcessor)
+        {
+            //Note: the polyphase channel source has already been added to the mChannelSources in getChannel() method
+
+            checkChannelizerConfiguration();
+
+            mPolyphaseChannelizer.addChannel(channelSource);
+            mSourceEventBroadcaster.broadcast(SourceEvent.channelCountChange(getTunerChannelCount()));
+
+            //If this is the first channel, register to start the sample buffers flowing
+            if(mPolyphaseChannelizer.getRegisteredChannelCount() == 1)
+            {
+                mReusableBufferProvider.addBufferListener(mBufferProcessor);
+                mPolyphaseChannelizer.start();
+                mBufferProcessor.start();
+            }
+        }
+    }
+
+    /**
+     * Stops/removes the channel source from receiving channelized sample buffers and deregisters from the tuner
+     * when this is the last channel being sourced.
+     *
+     * @param channelSource to stop
+     */
+    private void stopChannelSource(PolyphaseChannelSource channelSource)
+    {
+        synchronized(mBufferProcessor)
+        {
+            mChannelSources.remove(channelSource);
+            mPolyphaseChannelizer.removeChannel(channelSource);
+            mSourceEventBroadcaster.broadcast(SourceEvent.channelCountChange(getTunerChannelCount()));
+
+            //If this is the last/only channel, deregister to stop the sample buffers
+            if(mPolyphaseChannelizer.getRegisteredChannelCount() == 0)
+            {
+                mReusableBufferProvider.removeBufferListener(mBufferProcessor);
+                mBufferProcessor.stop();
+                mPolyphaseChannelizer.stop();
+            }
+        }
+
+        try
+        {
+            //Broadcast a stop sample stream notification in case this was a forced-stop so consumers are aware
+            channelSource.process(SourceEvent.stopSampleStreamNotification(channelSource));
+        }
+        catch(SourceException se)
+        {
+            //Do nothing
+        }
+    }
+
+    /**
+     * Process source events received from the source (ie tuner controller) for frequency and sample rate change
+     * notifications.
+     * @param sourceEvent to process
+     * @throws SourceException
+     */
+    @Override
+    public void process(SourceEvent sourceEvent) throws SourceException
+    {
+        switch(sourceEvent.getEvent())
+        {
+            case NOTIFICATION_FREQUENCY_CHANGE:
+                //Update channel calculator immediately so that channels can be allocated
+                mChannelCalculator.setCenterFrequency(sourceEvent.getValue().longValue());
+
+                //Defer channelizer configuration changes to be handled on the buffer processor thread
+                mBufferSourceEventMonitor.receive(sourceEvent);
+                break;
+            case NOTIFICATION_SAMPLE_RATE_CHANGE:
+                //Update channel calculator immediately so that channels can be allocated
+                double sampleRate = sourceEvent.getValue().doubleValue();
+                int channelCount = ComplexPolyphaseChannelizerM2.getChannelCount(sampleRate);
+                mChannelCalculator.setRates(sampleRate, channelCount);
+                break;
+            case NOTIFICATION_FREQUENCY_AND_SAMPLE_RATE_LOCKED:
+            case NOTIFICATION_FREQUENCY_AND_SAMPLE_RATE_UNLOCKED:
+            case NOTIFICATION_FREQUENCY_CORRECTION_CHANGE:
+                //no-op
+                break;
+            default:
+                mLog.info("Unrecognized source event: " + sourceEvent.toString());
+                break;
+        }
+    }
+
+    /**
+     * Creates or updates the channelizer to process the incoming sample rate and updates any channel processors.
+     *
+     * Note: this method should only be invoked on the mBufferProcessor thread or prior to starting the mBufferProcessor.
+     * Sample rate source events will normally arrive via the incoming complex buffer stream from the mBufferProcessor
+     * and will be handled as they arrive.
+     */
+    private void checkChannelizerConfiguration()
+    {
+        //Channel calculator is always in sync with the tuner's current sample rate
+        double tunerSampleRate = mChannelCalculator.getSampleRate();
+
+        //If the channelizer is not setup, or setup to the wrong sample rate, recreate it
+        if(mPolyphaseChannelizer == null || Math.abs(mPolyphaseChannelizer.getSampleRate() - tunerSampleRate) > 0.5)
+        {
+            if(mPolyphaseChannelizer != null && mPolyphaseChannelizer.getRegisteredChannelCount() > 0)
+            {
+                throw new IllegalStateException("Polyphase Channelizer cannot be changed to a new sample rate while " +
+                    "channels are currently sourced.  Ensure you remove all tuner channels before changing tuner " +
+                    "sample rate.  Current channel count:" +
+                    (mPolyphaseChannelizer != null ? mPolyphaseChannelizer.getRegisteredChannelCount() : "0"));
+            }
+
+            try
+            {
+                mPolyphaseChannelizer = new ComplexPolyphaseChannelizerM2(tunerSampleRate,
+                    POLYPHASE_CHANNELIZER_TAPS_PER_CHANNEL);
+            }
+            catch(IllegalArgumentException iae)
+            {
+                mLog.error("Could not create polyphase channelizer for sample rate [" + tunerSampleRate + "]", iae);
+            }
+            catch(FilterDesignException fde)
+            {
+                mLog.error("Could not create filter for polyphase channelizer for sample rate [" + tunerSampleRate + "]", fde);
+            }
+
+            //Clear any previous channel synthesis filters so they can be recreated for the new channel sample rate
+            mOutputProcessorFilters.clear();
+        }
+    }
+
+    /**
+     * Updates each of the output processors for any changes in the tuner's center frequency or sample rate, which
+     * would cause the output processors to change the polyphase channelizer results channel(s) that the processor is
+     * consuming
+     *
+     * @param sourceEvent (optional-can be null) to broadcast to each output processor following the update
+     */
+    private void updateOutputProcessors(SourceEvent sourceEvent)
+    {
+        for(PolyphaseChannelSource channelSource: mChannelSources)
+        {
+            updateOutputProcessor(channelSource);
+
+            //Send the non-null source event to each channel source
+            if(sourceEvent != null)
+            {
+                try
+                {
+                    channelSource.process(sourceEvent);
+                }
+                catch(SourceException se)
+                {
+                    mLog.error("Error while notifying polyphase channel source of a source event", se);
+                }
+            }
+        }
+    }
+
+    /**
+     * Updates the polyphase channel source's output processor due to a change in the center frequency or sample
+     * rate for the source providing sample buffers to the polyphase channelizer, or whenever the DDC channel's
+     * center tuned frequency changes.
+     *
+     * @param channelSource that requires an update to its output processor
+     */
+    private void updateOutputProcessor(PolyphaseChannelSource channelSource)
+    {
+        try
+        {
+            //If a change in sample rate or center frequency makes this channel no longer viable, then the channel
+            //calculator will throw an IllegalArgException ... handled below
+            List<Integer> indexes = mChannelCalculator.getChannelIndexes(channelSource.getTunerChannel());
+
+            long centerFrequency = mChannelCalculator.getCenterFrequencyForIndexes(indexes);
+
+            //If the indexes size is the same then update the current processor, otherwise create a new one
+            IPolyphaseChannelOutputProcessor outputProcessor = channelSource.getPolyphaseChannelOutputProcessor();
+
+            if(outputProcessor != null && outputProcessor.getInputChannelCount() == indexes.size())
+            {
+                channelSource.getPolyphaseChannelOutputProcessor().setPolyphaseChannelIndices(indexes);
+                channelSource.setFrequency(centerFrequency);
+
+                if(indexes.size() > 1)
+                {
+                    try
+                    {
+                        float[] filter = getOutputProcessorFilter(indexes.size());
+                        channelSource.getPolyphaseChannelOutputProcessor().setSynthesisFilter(filter);
+                    }
+                    catch(FilterDesignException fde)
+                    {
+                        mLog.error("Error creating an updated synthesis filter for the channel output processor");
+                    }
+                }
+            }
+            else
+            {
+                channelSource.setPolyphaseChannelOutputProcessor(getOutputProcessor(indexes), centerFrequency);
+            }
+        }
+        catch(IllegalArgumentException iae)
+        {
+            mLog.error("Error updating polyphase channel source - can't determine output channel indexes for " +
+                "updated tuner center frequency and sample rate.  Stopping channel source", iae);
+
+            stopChannelSource(channelSource);
+        }
+    }
+
+    /**
+     * Sorted set of currently sourced tuner channels being provided by this channel manager.  The set is ordered by
+     * frequency (low to high).
+     */
+    public SortedSet<TunerChannel> getTunerChannels()
+    {
+        SortedSet<TunerChannel> tunerChannels = new TreeSet<>();
+
+        for(PolyphaseChannelSource channelSource: mChannelSources)
+        {
+            tunerChannels.add(channelSource.getTunerChannel());
+        }
+
+        return tunerChannels;
+    }
+
+    /**
+     * Count of currently sourced tuner channels
+     */
+    public int getTunerChannelCount()
+    {
+        return mChannelSources.size();
+    }
+
+    /**
+     * Adds the listener to receive source events
+     */
+    public void addSourceEventListener(Listener<SourceEvent> listener)
+    {
+        mSourceEventBroadcaster.addListener(listener);
+    }
+
+    /**
+     * Removes the listener from receiving source events
+     */
+    public void removeSourceEventListener(Listener<SourceEvent> listener)
+    {
+        mSourceEventBroadcaster.removeListener(listener);
+    }
+
+    /**
+     * Generates (or reuses) an output processor filter for the specified number of channels.  Each
+     * filter is created only once and stored in a map for reuse.  This map is cleared anytime that the
+     * input sample rate changes, so that the filters can be recreated with the new channel sample rate.
+     * @param channels count
+     * @return filter
+     * @throws FilterDesignException if the filter cannot be designed to specification (-6 dB band edge)
+     */
+    private float[] getOutputProcessorFilter(int channels) throws FilterDesignException
+    {
+        float[] taps = mOutputProcessorFilters.get(channels);
+
+        if(taps == null)
+        {
+            taps = FilterFactory.getSincM2Synthesizer(mChannelCalculator.getChannelSampleRate(),
+                mChannelCalculator.getChannelBandwidth(), channels, POLYPHASE_SYNTHESIZER_TAPS_PER_CHANNEL);
+
+            mOutputProcessorFilters.put(channels, taps);
+        }
+
+        return taps;
+    }
+
+    /**
+     * Internal class for handling requests for start/stop sample stream from polyphase channel sources
+     */
+    private class ChannelSourceEventListener implements Listener<SourceEvent>
+    {
+        @Override
+        public void receive(SourceEvent sourceEvent)
+        {
+            switch(sourceEvent.getEvent())
+            {
+                case REQUEST_START_SAMPLE_STREAM:
+                    if(sourceEvent.hasSource() && sourceEvent.getSource() instanceof PolyphaseChannelSource)
+                    {
+                        startChannelSource((PolyphaseChannelSource)sourceEvent.getSource());
+                    }
+                    else
+                    {
+                        mLog.error("Request to start sample stream for unrecognized source: " +
+                            (sourceEvent.hasSource() ? sourceEvent.getSource().getClass() : "null source"));
+                    }
+                    break;
+                case REQUEST_STOP_SAMPLE_STREAM:
+                    if(sourceEvent.hasSource() && sourceEvent.getSource() instanceof PolyphaseChannelSource)
+                    {
+                        stopChannelSource((PolyphaseChannelSource)sourceEvent.getSource());
+                    }
+                    else
+                    {
+                        mLog.error("Request to stop sample stream for unrecognized source: " +
+                            (sourceEvent.hasSource() ? sourceEvent.getSource().getClass() : "null source"));
+                    }
+                    break;
+                case REQUEST_SOURCE_DISPOSE:
+                    Source source = sourceEvent.getSource();
+
+                    if(source instanceof PolyphaseChannelSource)
+                    {
+                        source.dispose();
+                    }
+                    break;
+                case NOTIFICATION_FREQUENCY_CORRECTION_CHANGE:
+                    //ignore
+                    break;
+                case NOTIFICATION_MEASURED_FREQUENCY_ERROR_SYNC_LOCKED:
+                    //Rebroadcast so that the tuner source can process this event
+                    mSourceEventBroadcaster.broadcast(sourceEvent);
+                    break;
+                default:
+                    mLog.error("Received unrecognized source event from polyphase channel source [" +
+                        sourceEvent.getEvent() + "]");
+                    break;
+            }
+        }
+    }
+
+    /**
+     * Processes the incoming buffer stream from the provider and transfers the buffers to the polyphase channelizer.
+     *
+     * This monitor incorporates a queue for receiving source events that affect configuration of the channelizer so
+     * that they can be processed on the buffer processor calling thread, avoiding unnecessary locks on the channelizer
+     * and/or the channel sources and output processors.
+     */
+    public class BufferSourceEventMonitor implements Listener<List<ReusableComplexBuffer>>
+    {
+        private Queue<SourceEvent> mQueuedSourceEvents = new ConcurrentLinkedQueue<>();
+
+        /**
+         * Queues the source event for deferred execution on the buffer processing thread.
+         * @param event that affects configuration of the channelizer (frequency or sample rate change events)
+         */
+        public void receive(SourceEvent event)
+        {
+            mQueuedSourceEvents.offer(event);
+        }
+
+        @Override
+        public void receive(List<ReusableComplexBuffer> reusableComplexBuffers)
+        {
+            try
+            {
+                //Process any queued source events before processing the buffers
+                SourceEvent queuedSourceEvent = mQueuedSourceEvents.poll();
+
+                while(queuedSourceEvent != null)
+                {
+                    switch(queuedSourceEvent.getEvent())
+                    {
+                        case NOTIFICATION_FREQUENCY_CHANGE:
+                            //Don't send the tuner's frequency change event down to the channels - it would cause chaos
+                            updateOutputProcessors(null);
+                            break;
+                    }
+
+                    queuedSourceEvent = mQueuedSourceEvents.poll();
+                }
+
+                for(ReusableComplexBuffer reusableComplexBuffer: reusableComplexBuffers)
+                {
+                    if(mPolyphaseChannelizer != null)
+                    {
+                        //User count management is handled by the channelizer
+                        mPolyphaseChannelizer.receive(reusableComplexBuffer);
+                    }
+                    else
+                    {
+                        reusableComplexBuffer.decrementUserCount();
+                    }
+                }
+            }
+            catch(Throwable throwable)
+            {
+                mLog.error("Error", throwable);
+                for(ReusableComplexBuffer buffer: reusableComplexBuffers)
+                {
+                    buffer.decrementUserCount();
+                }
+            }
+        }
+    }
+}

src/main/java/io/github/dsheirer/dsp/filter/channelizer/PolyphaseChannelSource.java

@@ -0,0 +1,251 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.filter.channelizer;
+
+import io.github.dsheirer.dsp.filter.channelizer.output.IPolyphaseChannelOutputProcessor;
+import io.github.dsheirer.sample.Listener;
+import io.github.dsheirer.sample.buffer.ReusableChannelResultsBuffer;
+import io.github.dsheirer.sample.buffer.ReusableComplexBuffer;
+import io.github.dsheirer.sample.buffer.ReusableComplexBufferAssembler;
+import io.github.dsheirer.source.SourceEvent;
+import io.github.dsheirer.source.tuner.channel.TunerChannel;
+import io.github.dsheirer.source.tuner.channel.TunerChannelSource;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class PolyphaseChannelSource extends TunerChannelSource
+{
+    private final static Logger mLog = LoggerFactory.getLogger(PolyphaseChannelSource.class);
+
+    private ReusableComplexBufferAssembler mReusableComplexBufferAssembler;
+    private IPolyphaseChannelOutputProcessor mPolyphaseChannelOutputProcessor;
+    private double mChannelSampleRate;
+    private long mIndexCenterFrequency;
+    private long mChannelFrequencyCorrection;
+
+    /**
+     * Polyphase channelizer tuner channel source implementation.  Adapts the channel array output samples from the
+     * polyphase channelizer into a single channel, or a channel synthesized from two adjacent channels that is
+     * frequency translated and decimated to a single channel.
+     *
+     * @param tunerChannel describing the desired channel frequency and bandwidth/minimum sample rate
+     * @param outputProcessor - to process polyphase channelizer channel results into a channel stream
+     * @param producerSourceEventListener to receive source event requests (e.g. start/stop sample stream)
+     * @param channelSampleRate for the downstream sample output
+     * @param centerFrequency of the incoming polyphase channel(s)
+     */
+    public PolyphaseChannelSource(TunerChannel tunerChannel, IPolyphaseChannelOutputProcessor outputProcessor,
+                                  Listener<SourceEvent> producerSourceEventListener, double channelSampleRate,
+                                  long centerFrequency)
+    {
+        super(producerSourceEventListener, tunerChannel);
+        mPolyphaseChannelOutputProcessor = outputProcessor;
+        mChannelSampleRate = channelSampleRate;
+        mReusableComplexBufferAssembler = new ReusableComplexBufferAssembler(2500, mChannelSampleRate);
+        setFrequency(centerFrequency);
+    }
+
+    /**
+     * Registers the listener to receive complex sample buffers from this channel source
+     */
+    @Override
+    public void setListener(final Listener<ReusableComplexBuffer> listener)
+    {
+        mReusableComplexBufferAssembler.setListener(listener);
+   }
+
+    /**
+     * Removes the listener from receiving complex sample buffers from this channel source
+     */
+    @Override
+    public void removeListener(Listener<ReusableComplexBuffer> listener)
+    {
+        mReusableComplexBufferAssembler.setListener(null);
+    }
+
+    /**
+     * Channel output processor used by this channel source to convert polyphase channel results into a specific
+     * channel complex buffer output stream.
+     */
+    public IPolyphaseChannelOutputProcessor getPolyphaseChannelOutputProcessor()
+    {
+        return mPolyphaseChannelOutputProcessor;
+    }
+
+    /**
+     * Sets/updates the output processor for this channel source, replacing the existing output processor.
+     *
+     * @param outputProcessor to use
+     * @param frequency center for the channels processed by the output processor
+     */
+    public void setPolyphaseChannelOutputProcessor(IPolyphaseChannelOutputProcessor outputProcessor, long frequency)
+    {
+        //Lock on the channel output processor to block the channel results processor thread from servicing the
+        //channel output processor's buffer while we change out the processors.
+        synchronized(mPolyphaseChannelOutputProcessor)
+        {
+            IPolyphaseChannelOutputProcessor existingProcessor = mPolyphaseChannelOutputProcessor;
+
+            //Swap out the processor so that incoming samples can accumulate in the new channel output processor
+            mPolyphaseChannelOutputProcessor = outputProcessor;
+
+            //Remove the buffer overflow listener and clear any previous buffer overflow state
+            existingProcessor.setSourceOverflowListener(null);
+            broadcastOverflowState(false);
+
+            //Register to receive buffer overflow notifications so we can push them up through the source chain
+            mPolyphaseChannelOutputProcessor.setSourceOverflowListener(this);
+
+            //Fully process the residual channel results buffer of the previous channel output processor
+            if(existingProcessor != null)
+            {
+                existingProcessor.processChannelResults(mReusableComplexBufferAssembler);
+            }
+
+            //Finally, setup the frequency offset for the output processor and reset the frequency correction value
+            //to allow consumers to adjust and calculate a new frequency correction value, if needed.
+            mIndexCenterFrequency = frequency;
+            mChannelFrequencyCorrection = 0;
+            mPolyphaseChannelOutputProcessor.setFrequencyOffset(getFrequencyOffset());
+            broadcastConsumerSourceEvent(SourceEvent.frequencyCorrectionChange(mChannelFrequencyCorrection));
+        }
+    }
+
+    /**
+     * Primary method for receiving channel results output from a polyphase channelizer.  The results buffer will be
+     * queued for processing to extract the target channel samples, process them for frequency correction and/or
+     * channel aggregation, and dispatch the results to the downstream sample listener/consumer.
+     *
+     * @param channelResultsBuffer containing an array of polyphase channelizer outputs.
+     */
+    public void receiveChannelResults(ReusableChannelResultsBuffer channelResultsBuffer)
+    {
+        mReusableComplexBufferAssembler.updateTimestamp(channelResultsBuffer.getTimestamp());
+
+        if(mPolyphaseChannelOutputProcessor != null)
+        {
+            mPolyphaseChannelOutputProcessor.receiveChannelResults(channelResultsBuffer);
+        }
+    }
+
+    /**
+     * Downstream channel sample rate
+     *
+     * @return sample rate in Hertz
+     */
+    @Override
+    public double getSampleRate()
+    {
+        return mChannelSampleRate;
+    }
+
+    /**
+     * Sets the downstream channel sample rate
+     * @param sampleRate in hertz
+     */
+    @Override
+    protected void setSampleRate(double sampleRate)
+    {
+        mChannelSampleRate = sampleRate;
+    }
+
+    @Override
+    public void dispose()
+    {
+        if(mReusableComplexBufferAssembler != null)
+        {
+            mReusableComplexBufferAssembler.dispose();
+        }
+
+        if(mPolyphaseChannelOutputProcessor != null)
+        {
+            mPolyphaseChannelOutputProcessor.dispose();
+            mPolyphaseChannelOutputProcessor = null;
+        }
+    }
+
+    @Override
+    public long getChannelFrequencyCorrection()
+    {
+        return mChannelFrequencyCorrection;
+    }
+
+    /**
+     * Adjusts the frequency correction value that is being applied to the channelized output stream by the
+     * polyphase channel output processor.
+     *
+     * @param value to apply for frequency correction in hertz
+     */
+    protected void setChannelFrequencyCorrection(long value)
+    {
+        mChannelFrequencyCorrection = value;
+        updateFrequencyOffset();
+        broadcastConsumerSourceEvent(SourceEvent.frequencyCorrectionChange(mChannelFrequencyCorrection));
+    }
+
+    /**
+     * Sets the center frequency for this channel.frequency for the incoming sample stream channel results and resets frequency correction to zero.
+     * @param frequency in hertz
+     */
+    @Override
+    public void setFrequency(long frequency)
+    {
+        mIndexCenterFrequency = frequency;
+
+        //Set frequency correction to zero to trigger an update to the mixer and allow downstream monitors to
+        //recalculate the frequency error correction again
+        setChannelFrequencyCorrection(0);
+    }
+
+    @Override
+    protected void processSamples()
+    {
+        //Lock on the output processor so that it can't be changed in the middle of processing
+        synchronized(mPolyphaseChannelOutputProcessor)
+        {
+            mPolyphaseChannelOutputProcessor.processChannelResults(mReusableComplexBufferAssembler);
+        }
+    }
+
+    /**
+     * Calculates the frequency offset required to mix the incoming signal to center the desired frequency
+     * within the channel
+     */
+    private long getFrequencyOffset()
+    {
+        return mIndexCenterFrequency - getTunerChannel().getFrequency() + mChannelFrequencyCorrection;
+    }
+
+    /**
+     * Updates the frequency offset being applied by the output processor.  Calculates the offset using the center
+     * frequency of the incoming polyphase channel results and the desired output channel frequency adjusted by any
+     * requested frequency correction value.
+     */
+    private void updateFrequencyOffset()
+    {
+        synchronized(mPolyphaseChannelOutputProcessor)
+        {
+            mPolyphaseChannelOutputProcessor.setFrequencyOffset(getFrequencyOffset());
+        }
+    }
+
+    @Override
+    public String toString()
+    {
+        return "POLYPHASE [" + mPolyphaseChannelOutputProcessor.getInputChannelCount() + "] " +
+            getTunerChannel().getFrequency();
+    }
+}

src/main/java/io/github/dsheirer/dsp/filter/channelizer/SampleTimestampManager.java

@@ -0,0 +1,83 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.filter.channelizer;
+
+public class SampleTimestampManager
+{
+    private long mReferenceTimestamp = System.currentTimeMillis();
+    private double mSamplesPerMilliSecond;
+    private long mSampleCount;
+
+    /**
+     * Tracks the number of samples produced relative to a reference timestamp to derive a current reference timestamp
+     * for use in generating sample buffers.
+     *
+     * @param sampleRate per second
+     */
+    public SampleTimestampManager(double sampleRate)
+    {
+    }
+
+    /**
+     * Updates the internal reference timestamp and resets the sample counter to zero.
+     *
+     * @param referenceTimestamp in milli-seconds since epoch
+     */
+    public void setReferenceTimestamp(long referenceTimestamp)
+    {
+        mReferenceTimestamp = referenceTimestamp;
+        mSampleCount = 0;
+    }
+
+    /**
+     * Updates the sample rate that is used in calculating the reference timestamp
+     *
+     * @param sampleRate
+     */
+    public void setSampleRate(double sampleRate)
+    {
+        //Convert to samples per milli-second for compatibility with reference timestamp
+        mSamplesPerMilliSecond = sampleRate / 1000.0d;
+    }
+
+    /**
+     * Increments the internal count of dispatched samples to use in calculating an accurate reference timestamp.
+     */
+    public void increment()
+    {
+        mSampleCount++;
+    }
+
+    /**
+     * Increments the internal count of dispatched samples to use in calculating an accurate reference timestamp.
+     *
+     * @param value to add to the sample count
+     */
+    public void increment(int value)
+    {
+        mSampleCount += value;
+    }
+
+    public long getCurrentTimestamp()
+    {
+        if(mSampleCount > 0)
+        {
+            return mReferenceTimestamp + (long)((double)mSampleCount / mSamplesPerMilliSecond);
+        }
+
+        return mReferenceTimestamp;
+    }
+}

src/main/java/io/github/dsheirer/dsp/filter/channelizer/TwoChannelSynthesizerM2.java

@@ -0,0 +1,191 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.filter.channelizer;
+
+import io.github.dsheirer.sample.buffer.ReusableComplexBuffer;
+import io.github.dsheirer.sample.buffer.ReusableComplexBufferQueue;
+import org.jtransforms.fft.FloatFFT_1D;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Implements a two-channel polyphase filer synthesizer.  This class is intended to be used with an M2 polyphase
+ * channelizer in order to recover a signal that overlaps the boundary between two channels.  This synthesizer will
+ * rejoin the two M2 neighboring channels, mix the signal of interest to baseband, and filter the output stream to
+ * half of the sample rate, producing an overall M2 output sample rate.
+ *
+ * The synthesizer concept is modeled on the structure described by Fred Harris et al, in 'Interleaving Different
+ * Bandwidth Narrowband Channels in Perfect Reconstruction Cascade Polyphase Filter Banks for Efficient Flexible
+ * Variable Bandwidth Filters in Wideband Digital Transceivers'.
+ *
+ * The data buffers and sub-filter kernels bear some resemblance to the structures defined in the paper.  The data and
+ * filter structures in this class are organized to take advantage of Java's ability to leverage SIMD processor
+ * intrinsics for optimal efficiency in processing.  The paper specifies splitting the filter kernel into N polyphase
+ * partitions and creating N data buffers.  This class organizes the data buffer as a contiguous sample
+ * array and creates an I/Q interleaved filter kernel.  Instead of calculating the dot-product for each sub-filter,
+ * we calculate the product of the full data array against the filter and then accumulate each sub-filter.  This allows
+ * java to use SIMD for the array product and then normal processing for the accumulation.  Since this is a two-channel
+ * processor and the results of each filter accumulation are added, we use a single accumulator across both filters.
+ *
+ */
+public class TwoChannelSynthesizerM2
+{
+    private final static Logger mLog = LoggerFactory.getLogger(TwoChannelSynthesizerM2.class);
+
+    private ReusableComplexBufferQueue mReusableComplexBufferQueue = new ReusableComplexBufferQueue("Two Channel Synthesizer M2");
+    private float[] mSerpentineDataBuffer;
+    private float[] mIQInterleavedFilter;
+    private float[] mFilterVectorProduct;
+    private float[] mIFFTBuffer = new float[4];
+    private float mIAccumulator;
+    private float mQAccumulator;
+    private FloatFFT_1D mFFT = new FloatFFT_1D(2);
+    private boolean mTopBlockFlag = true;
+
+    /**
+     * Polyphase synthesizer for mixing two M2 oversampled channels into a composite channel using perfect
+     * reconstruction filters (-6db at band edge).  Output sample rate is the same as the input sample rate of one of
+     * the channels.
+     */
+    public TwoChannelSynthesizerM2(float[] filter)
+    {
+        init(filter);
+    }
+
+    /**
+     * Initializes the synthesizer filter and data buffers for operation.
+     *
+     * @param filter to use for polyphase synthesis of two channels.
+     */
+    private void init(float[] filter)
+    {
+        int tapsPerChannel = (int)Math.ceil(filter.length / 2);
+
+        mIQInterleavedFilter = getInterleavedFilter(filter, tapsPerChannel);
+        mSerpentineDataBuffer = new float[mIQInterleavedFilter.length];
+        mFilterVectorProduct = new float[mIQInterleavedFilter.length];
+    }
+
+    /**
+     * Synthesizes a new channel from the channel 1 and channel 2 sample arrays that are arranged as
+     * i0, q0, i1, q1 ... iN-1, qN-1
+     *
+     * @param channelBuffer1 input channel
+     * @param channelBuffer2 input channel
+     * @return synthesized channel results of the same length as both channel 1/2 input arrays.
+     */
+    public ReusableComplexBuffer process(ReusableComplexBuffer channelBuffer1, ReusableComplexBuffer channelBuffer2)
+    {
+        if(channelBuffer1.getSamples().length != channelBuffer1.getSamples().length)
+        {
+            throw new IllegalArgumentException("Channel 1 and 2 array length must be equal");
+        }
+
+        float[] channel1 = channelBuffer1.getSamples();
+        float[] channel2 = channelBuffer2.getSamples();
+
+        ReusableComplexBuffer synthesizedComplexBuffer = mReusableComplexBufferQueue.getBuffer(channel1.length);
+
+        float[] output = synthesizedComplexBuffer.getSamples();
+
+        for(int x = 0; x < channel1.length; x += 2)
+        {
+            //Load samples from each channel into buffer for IFFT
+            mIFFTBuffer[0] = channel1[x];     //i
+            mIFFTBuffer[1] = channel1[x + 1]; //q
+            mIFFTBuffer[2] = channel2[x];     //i
+            mIFFTBuffer[3] = channel2[x + 1]; //q
+
+            //Perform Inverse FFT (IFFT)
+            mFFT.complexInverse(mIFFTBuffer, true);
+
+            //Perform serpentine shift of data blocks in the data buffer - make room for 4 new samples
+            System.arraycopy(mSerpentineDataBuffer, 0, mSerpentineDataBuffer, 4, mSerpentineDataBuffer.length - 4);
+
+            //Top Block - load samples into data buffer in normal order
+            if(mTopBlockFlag)
+            {
+                System.arraycopy(mIFFTBuffer, 0, mSerpentineDataBuffer, 0, mIFFTBuffer.length);
+            }
+            //Bottom Block - swap samples via data loading to account for phase shift
+            else
+            {
+                System.arraycopy(mIFFTBuffer, 0, mSerpentineDataBuffer, 2, 2);
+                System.arraycopy(mIFFTBuffer, 2, mSerpentineDataBuffer, 0, 2);
+            }
+
+            //Note: in order to use Java's ability to leverage SIMD intrinsics, we perform filtering in two steps
+            //(multiply then accumulate) since our filter and data are structured with I and Q vectors interleaved.
+            //This approach allows the Hotspot compiler to more easily recognize the scalor operations.
+
+            //Multiply data samples by the I/Q interleaved filter to form the vector product
+            for(int y = 0; y < mSerpentineDataBuffer.length; y++)
+            {
+                mFilterVectorProduct[y] = mSerpentineDataBuffer[y] * mIQInterleavedFilter[y];
+            }
+
+            //Accumulate output I/Q samples from vector product
+            mIAccumulator = 0.0f;
+            mQAccumulator = 0.0f;
+
+            for(int y = 0; y < mFilterVectorProduct.length; y += 2)
+            {
+                mIAccumulator += mFilterVectorProduct[y];
+                mQAccumulator += mFilterVectorProduct[y + 1];
+            }
+
+            output[x] = mIAccumulator;
+            output[x + 1] = mQAccumulator;
+
+            mTopBlockFlag = !mTopBlockFlag;
+        }
+
+        channelBuffer1.decrementUserCount();
+        channelBuffer2.decrementUserCount();
+
+        return synthesizedComplexBuffer;
+    }
+
+    /**
+     * Creates an interleaved I/Q filter where each coefficient from the filter argument is duplicated and the returned
+     * filter is twice the length of the original filter.
+     *
+     * Note: the returned filter array is sized to:  2 * channel count * taps per channel, which may be slightly more
+     * than twice the length of the original filter.  Any Added filter array elements will contain zero values.
+     *
+     * @param coefficients to create an interleaved filter
+     * @param tapsPerChannel count
+     * @return
+     */
+    private static float[] getInterleavedFilter(float[] coefficients, int tapsPerChannel)
+    {
+        int channelCount = 2;
+
+        float[] filter = new float[channelCount * tapsPerChannel * 2];
+
+        int coefficientPointer = 0;
+        int filterPointer = 0;
+
+        //Create a new filter that duplicates each tap to produce an interleaved I/Q filter
+        while(coefficientPointer < coefficients.length)
+        {
+            filter[filterPointer++] = coefficients[coefficientPointer];
+            filter[filterPointer++] = coefficients[coefficientPointer++];
+        }
+
+        return filter;
+    }
+}

src/main/java/io/github/dsheirer/dsp/filter/channelizer/output/ChannelOutputProcessor.java

@@ -0,0 +1,174 @@
+/*******************************************************************************
+ * sdrtrunk
+ * Copyright (C) 2014-2017 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.filter.channelizer.output;
+
+import io.github.dsheirer.dsp.mixer.IOscillator;
+import io.github.dsheirer.dsp.mixer.Oscillator;
+import io.github.dsheirer.sample.IOverflowListener;
+import io.github.dsheirer.sample.buffer.OverflowableReusableBufferTransferQueue;
+import io.github.dsheirer.sample.buffer.ReusableChannelResultsBuffer;
+import io.github.dsheirer.sample.buffer.ReusableComplexBufferAssembler;
+import io.github.dsheirer.source.Source;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public abstract class ChannelOutputProcessor implements IPolyphaseChannelOutputProcessor
+{
+    private final static Logger mLog = LoggerFactory.getLogger(ChannelOutputProcessor.class);
+
+    private OverflowableReusableBufferTransferQueue<ReusableChannelResultsBuffer> mChannelResultsQueue;
+    private List<ReusableChannelResultsBuffer> mChannelResultsToProcess = new ArrayList<>();
+    private int mMaxResultsToProcess;
+
+    private int mInputChannelCount;
+    private IOscillator mFrequencyCorrectionMixer;
+    private boolean mFrequencyCorrectionEnabled;
+    private double mGain = 1.0;
+
+    /**
+     * Base class for polyphase channelizer output channel processing.  Provides built-in frequency translation
+     * oscillator support to apply frequency correction to the channel sample stream as requested by sample consumer.
+     *
+     * @param inputChannelCount is the number of input channels for this output processor
+     * @param sampleRate of the output channel.  This is used to match the oscillator's sample rate to the output
+     * channel sample rate for frequency translation/correction.
+     */
+    public ChannelOutputProcessor(int inputChannelCount, double sampleRate, double gain)
+    {
+        mInputChannelCount = inputChannelCount;
+        mGain = gain;
+
+//TODO: swap this out and use the LowPhaseNoiseOscillator
+        mFrequencyCorrectionMixer = new Oscillator(0, sampleRate);
+        mMaxResultsToProcess = (int)(sampleRate / 10) * 2;  //process at 100 millis interval, twice the expected inflow rate
+
+        mChannelResultsQueue = new OverflowableReusableBufferTransferQueue<>((int)(sampleRate * 3), (int)(sampleRate * 0.5));
+    }
+
+    protected double getGain()
+    {
+        return mGain;
+    }
+
+    @Override
+    public int getPolyphaseChannelIndexCount()
+    {
+        return mInputChannelCount;
+    }
+
+    public void dispose()
+    {
+        if(mChannelResultsQueue != null)
+        {
+            mChannelResultsQueue.dispose();
+            mChannelResultsQueue = null;
+        }
+    }
+
+    /**
+     * Sets the frequency offset to apply to the incoming samples to mix the desired signal to baseband.
+     * @param frequencyOffset in hertz
+     */
+    @Override
+    public void setFrequencyOffset(long frequencyOffset)
+    {
+        mFrequencyCorrectionMixer.setFrequency(frequencyOffset);
+        mFrequencyCorrectionEnabled = (frequencyOffset != 0);
+    }
+
+    /**
+     * Oscillator/mixer to use for frequency correction against incoming sample stream
+     */
+    protected IOscillator getFrequencyCorrectionMixer()
+    {
+        return mFrequencyCorrectionMixer;
+    }
+
+    @Override
+    public void receiveChannelResults(ReusableChannelResultsBuffer channelResults)
+    {
+        mChannelResultsQueue.offer(channelResults);
+    }
+
+    /**
+     * Processes all enqueued polyphase channelizer results until the internal queue is empty
+     * @param reusableComplexBufferAssembler to receive the processed channel results
+     */
+    @Override
+    public void processChannelResults(ReusableComplexBufferAssembler reusableComplexBufferAssembler)
+    {
+        try
+        {
+            int toProcess = mChannelResultsQueue.drainTo(mChannelResultsToProcess, mMaxResultsToProcess);
+
+            if(toProcess > 0)
+            {
+                process(mChannelResultsToProcess, reusableComplexBufferAssembler);
+            }
+        }
+        catch(Throwable throwable)
+        {
+            mLog.error("Error while processing polyphase channel samples", throwable);
+        }
+
+        mChannelResultsToProcess.clear();
+    }
+
+    /**
+     * Sub-class implementation to process one polyphase channelizer result array.
+     * @param channelResults to process
+     * @param reusableComplexBufferAssembler to receive the processed channelizer results
+     */
+    public abstract void process(List<ReusableChannelResultsBuffer> channelResults,
+                                 ReusableComplexBufferAssembler reusableComplexBufferAssembler);
+
+
+    /**
+     * Sets the overflow listener to monitor the internal channelizer channel results queue overflow state
+     */
+    public void setSourceOverflowListener(Source source)
+    {
+        mChannelResultsQueue.setSourceOverflowListener(source);
+    }
+
+    /**
+     * Removes the overflow listener from monitoring the internal channelizer channel results queue overflow state
+     */
+    public void removeOverflowListener(IOverflowListener listener)
+    {
+        mChannelResultsQueue.setOverflowListener(null);
+    }
+
+    @Override
+    public int getInputChannelCount()
+    {
+        return mInputChannelCount;
+    }
+
+    /**
+     * Indicates if this channel has a frequency correction offset
+     */
+    public boolean hasFrequencyCorrection()
+    {
+        return mFrequencyCorrectionEnabled;
+    }
+}

src/main/java/io/github/dsheirer/dsp/filter/channelizer/output/IPolyphaseChannelOutputProcessor.java

@@ -0,0 +1,81 @@
+/*******************************************************************************
+ * sdrtrunk
+ * Copyright (C) 2014-2017 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.filter.channelizer.output;
+
+import io.github.dsheirer.sample.buffer.ReusableChannelResultsBuffer;
+import io.github.dsheirer.sample.buffer.ReusableComplexBufferAssembler;
+import io.github.dsheirer.source.Source;
+
+import java.util.List;
+
+public interface IPolyphaseChannelOutputProcessor
+{
+    /**
+     * Receive and enqueue output results from the polyphase analysis channelizer
+     * @param channelResultsBuffer to enqueue
+     */
+    void receiveChannelResults(ReusableChannelResultsBuffer channelResultsBuffer);
+
+    /**
+     * Process the channel output channel results queue and deliver the output to the listener
+     *
+     * @param reusableComplexBufferAssembler to receive the processed channel results
+     */
+    void processChannelResults(ReusableComplexBufferAssembler reusableComplexBufferAssembler);
+
+    /**
+     * Sets the desired frequency offset from center.  The samples will be mixed with an oscillator set to this offset
+     * frequency to produce an output where the desired signal is centered in the passband.
+     *
+     * @param frequency in hertz
+     */
+    void setFrequencyOffset(long frequency);
+
+    /**
+     * Indicates the number of input channels processed by this output processor
+     * @return
+     */
+    int getInputChannelCount();
+
+    /**
+     * Updates the input polyphase channel index(es) used by this output processor
+     * @param indexes
+     */
+    void setPolyphaseChannelIndices(List<Integer> indexes);
+
+    /**
+     * List of current polyphase channel indices for the output processor
+     */
+    int getPolyphaseChannelIndexCount();
+
+    /**
+     * Updates the synthesis filter taps for this output processor
+     * @param filter
+     */
+    void setSynthesisFilter(float[] filter);
+
+    /**
+     * Sets the listener to receive buffer overflow notifications
+     * @param source to receive overflow notifications
+     */
+    void setSourceOverflowListener(Source source);
+
+
+    void dispose();
+}

src/main/java/io/github/dsheirer/dsp/filter/channelizer/output/OneChannelOutputProcessor.java

@@ -0,0 +1,107 @@
+/*******************************************************************************
+ * sdrtrunk
+ * Copyright (C) 2014-2017 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.filter.channelizer.output;
+
+import io.github.dsheirer.sample.buffer.ReusableChannelResultsBuffer;
+import io.github.dsheirer.sample.buffer.ReusableComplexBuffer;
+import io.github.dsheirer.sample.buffer.ReusableComplexBufferAssembler;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.List;
+
+public class OneChannelOutputProcessor extends ChannelOutputProcessor
+{
+    private final static Logger mLog = LoggerFactory.getLogger(OneChannelOutputProcessor.class);
+
+    private int mChannelOffset;
+
+    /**
+     * Processor to extract a single channel from a polyphase channelizer and produce an output I/Q complex sample
+     * from each polyphase channelizer output results array.
+     *
+     * @param sampleRate of the output sample stream.
+     * @param channelIndexes containing a single channel index.
+     * @param gain value to apply.  Typically this is the same as the channelizer's channel count.
+     */
+    public OneChannelOutputProcessor(double sampleRate, List<Integer> channelIndexes, double gain)
+    {
+        super(1, sampleRate, gain);
+        setPolyphaseChannelIndices(channelIndexes);
+    }
+
+    @Override
+    public void setSynthesisFilter(float[] filter)
+    {
+        throw new IllegalArgumentException("The one channel output processor does not support filter updates");
+    }
+
+    /**
+     * Updates this processor to extract a single, specified channel index.
+     * @param indexes containing a single channel index value.
+     * @throws IllegalArgumentException if the list of indexes does not contain a single channel index.
+     */
+    public void setPolyphaseChannelIndices(List<Integer> indexes)
+    {
+        if(indexes.size() != 1)
+        {
+            throw new IllegalArgumentException("Single channel output processor requires a single index to " +
+                "process - provided indexes " + indexes.toString());
+        }
+
+        //Set the channelized output results offset to twice the channel index to account for each channel having
+        //an I/Q pair
+        mChannelOffset = indexes.get(0) * 2;
+    }
+
+    /**
+     * Extract the channel from the channel results array, apply frequency translation, and deliver the
+     * extracted frequency-corrected channel I/Q sample set to the complex sample listener.
+     *
+     * @param channelResults to process containing a list of channel array of I/Q sample pairs (I0,Q0,I1,Q1...In,Qn)
+     * @param reusableComplexBufferAssembler to receive the extracted, frequency-translated channel results
+     */
+    @Override
+    public void process(List<ReusableChannelResultsBuffer> channelResults,
+                        ReusableComplexBufferAssembler reusableComplexBufferAssembler)
+    {
+        for(ReusableChannelResultsBuffer channelResultsBuffer: channelResults)
+        {
+            try
+            {
+                ReusableComplexBuffer channelBuffer = channelResultsBuffer.getChannel(mChannelOffset);
+
+                if(hasFrequencyCorrection())
+                {
+                    getFrequencyCorrectionMixer().mixComplex(channelBuffer.getSamples());
+                }
+
+                channelBuffer.applyGain(getGain());
+
+                reusableComplexBufferAssembler.receive(channelBuffer);
+            }
+            catch(IllegalArgumentException iae)
+            {
+                mLog.error("Error extracting channel samples from polyphase channel results buffer");
+            }
+
+            channelResultsBuffer.decrementUserCount();
+        }
+    }
+}

src/main/java/io/github/dsheirer/dsp/filter/channelizer/output/TwoChannelOutputProcessor.java

@@ -0,0 +1,187 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.filter.channelizer.output;
+
+import io.github.dsheirer.dsp.filter.channelizer.TwoChannelSynthesizerM2;
+import io.github.dsheirer.dsp.filter.design.FilterDesignException;
+import io.github.dsheirer.dsp.filter.fir.FIRFilterSpecification;
+import io.github.dsheirer.dsp.filter.fir.complex.ComplexFIRFilter2;
+import io.github.dsheirer.dsp.filter.fir.remez.RemezFIRFilterDesigner;
+import io.github.dsheirer.dsp.mixer.FS4DownConverter;
+import io.github.dsheirer.sample.buffer.ReusableChannelResultsBuffer;
+import io.github.dsheirer.sample.buffer.ReusableComplexBuffer;
+import io.github.dsheirer.sample.buffer.ReusableComplexBufferAssembler;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class TwoChannelOutputProcessor extends ChannelOutputProcessor
+{
+    private final static Logger mLog = LoggerFactory.getLogger(TwoChannelOutputProcessor.class);
+
+    private static Map<Integer,float[]> sLowPassFilterKernelMap = new HashMap<>();
+    private TwoChannelSynthesizerM2 mSynthesizer;
+    private FS4DownConverter mFS4DownConverter = new FS4DownConverter();
+    private ComplexFIRFilter2 mLowPassFilter;
+
+    private int mChannelOffset1;
+    private int mChannelOffset2;
+
+    /**
+     * Processor to extract two channels from a polyphase channelizer, synthesize/recombine the channels, apply
+     * frequency translation and frequency correction, down-sample by a factor of two and output an I/Q complex sample.
+     *
+     * @param sampleRate of the output sample stream.
+     * @param channelIndexes containing two channel indices.
+     * @param gain to apply to output.  Typically this is equal to the channelizer's channel count.
+     */
+    public TwoChannelOutputProcessor(double sampleRate, List<Integer> channelIndexes, float[] filter, double gain)
+    {
+        //Set the frequency correction oscillator to 2 x output sample rate since we'll be correcting the frequency
+        //after synthesizing both input channels
+        super(2, sampleRate, gain);
+        setPolyphaseChannelIndices(channelIndexes);
+        setSynthesisFilter(filter);
+
+        float[] lowPassFilter = sLowPassFilterKernelMap.get((int)sampleRate);
+
+        if(lowPassFilter == null)
+        {
+            try
+            {
+                lowPassFilter = getLowPassFilter(sampleRate);
+                sLowPassFilterKernelMap.put((int)sampleRate, lowPassFilter);
+            }
+            catch(FilterDesignException fde)
+            {
+                mLog.error("Couldn't design a low-pass filter for 2-channel synthesizer", fde);
+                throw new IllegalStateException("Cannot design low-pass filter for 2 channel synthesizer", fde);
+            }
+        }
+
+        mLowPassFilter = new ComplexFIRFilter2(lowPassFilter, 1.0f);
+    }
+
+    /**
+     * Sets the frequency offset to apply to the incoming samples to mix the desired signal to baseband.
+     * @param frequencyOffset in hertz
+     */
+    @Override
+    public void setFrequencyOffset(long frequencyOffset)
+    {
+        super.setFrequencyOffset(frequencyOffset);
+    }
+
+
+    @Override
+    public void setSynthesisFilter(float[] filter)
+    {
+        mSynthesizer = new TwoChannelSynthesizerM2(filter);
+    }
+
+    /**
+     * Updates this processor to extract the two specified channel indexes.
+     *
+     * @param indexes containing a single channel index value.
+     * @throws IllegalArgumentException if the list of indexes does not contain a single channel index.
+     */
+    public void setPolyphaseChannelIndices(List<Integer> indexes)
+    {
+        if(indexes.size() != 2)
+        {
+            throw new IllegalArgumentException("Double channel output processor requires two indexes to " +
+                "process - provided indexes " + indexes.toString());
+        }
+
+        //Set the channelized output results offsets to twice the channel index to account for each channel having
+        //an I/Q pair
+        mChannelOffset1 = indexes.get(0) * 2;
+        mChannelOffset2 = indexes.get(1) * 2;
+    }
+
+    /**
+     * Extract the channel from the channel results array, apply frequency translation, and deliver the
+     * extracted frequency-corrected channel I/Q sample set to the complex sample listener.
+     *
+     * @param channelResultsBuffers to process containing an array of channel I/Q sample pairs (I0,Q0,I1,Q1...In,Qn)
+     * @param reusableComplexBufferAssembler to receive the extracted, frequency-translated channel results
+     */
+    @Override
+    public void process(List<ReusableChannelResultsBuffer> channelResultsBuffers,
+                        ReusableComplexBufferAssembler reusableComplexBufferAssembler)
+    {
+        for(ReusableChannelResultsBuffer buffer: channelResultsBuffers)
+        {
+            ReusableComplexBuffer channel1 = buffer.getChannel(mChannelOffset1);
+            ReusableComplexBuffer channel2 = buffer.getChannel(mChannelOffset2);
+
+            //Join the two channels using the synthesizer
+            ReusableComplexBuffer synthesized = mSynthesizer.process(channel1, channel2);
+
+            //The synthesized channels are centered at +FS/4 ... downconvert to center the spectrum
+            mFS4DownConverter.mixComplex(synthesized.getSamples());
+
+            //Apply offset and frequency correction to center the signal of interest within the synthesized channel
+            getFrequencyCorrectionMixer().mixComplex(synthesized.getSamples());
+
+            ReusableComplexBuffer lowPassFiltered = mLowPassFilter.filter(synthesized);
+
+            lowPassFiltered.applyGain(getGain());
+
+            reusableComplexBufferAssembler.receive(lowPassFiltered);
+
+            buffer.decrementUserCount();
+        }
+    }
+
+    /**
+     * Creates a low-pass filter kernel for the specified sample rate.
+     * @param sampleRate for the channel
+     * @return filter
+     * @throws FilterDesignException if the filter cannot be designed
+     */
+    private static float[] getLowPassFilter(double sampleRate) throws FilterDesignException
+    {
+        double cutoff = sampleRate / 4.0;
+        int passBandCutoff = (int)(cutoff * 0.92);
+        int stopBandStart = (int)(cutoff * 1.08);
+
+        FIRFilterSpecification specification = FIRFilterSpecification.lowPassBuilder()
+            .sampleRate(sampleRate)
+            .gridDensity(16)
+            .oddLength(true)
+            .passBandCutoff((int)passBandCutoff)
+            .passBandAmplitude(1.0)
+            .passBandRipple(0.01)
+            .stopBandStart((int)stopBandStart)
+            .stopBandAmplitude(0.0)
+            .stopBandRipple(0.005) //Approximately 94 dB attenuation
+            .build();
+
+        RemezFIRFilterDesigner designer = new RemezFIRFilterDesigner(specification);
+
+        if(designer.isValid())
+        {
+            return designer.getImpulseResponse();
+        }
+
+        throw new FilterDesignException("Couldn't design low-pass filter for sample rate: " + sampleRate +
+            " Pass End:" + passBandCutoff + " Stop Begin:" + stopBandStart);
+    }
+}

src/main/java/io/github/dsheirer/dsp/filter/cic/ComplexPrimeCICDecimate.java

@@ -1,82 +1,119 @@
 /*******************************************************************************
- * sdrtrunk
- * Copyright (C) 2014-2017 Dennis Sheirer
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
  *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
  *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
  *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
  *
  ******************************************************************************/
 package io.github.dsheirer.dsp.filter.cic;
 
-import io.github.dsheirer.dsp.filter.FilterFactory;
-import io.github.dsheirer.dsp.filter.Filters;
-import io.github.dsheirer.dsp.filter.Window;
-import io.github.dsheirer.dsp.filter.fir.complex.ComplexFIRFilter_CB_CB;
-import io.github.dsheirer.dsp.filter.halfband.complex.HalfBandFilter_CB_CB;
+import io.github.dsheirer.dsp.filter.design.FilterDesignException;
+import io.github.dsheirer.dsp.filter.fir.FIRFilterSpecification;
+import io.github.dsheirer.dsp.filter.fir.complex.ComplexFIRFilter2;
+import io.github.dsheirer.dsp.filter.fir.remez.RemezFIRFilterDesigner;
 import io.github.dsheirer.sample.Listener;
-import io.github.dsheirer.sample.complex.ComplexBuffer;
+import io.github.dsheirer.sample.buffer.ReusableComplexBuffer;
+import io.github.dsheirer.sample.buffer.ReusableComplexBufferAssembler;
 import io.github.dsheirer.sample.complex.ComplexSampleListener;
-import io.github.dsheirer.sample.complex.ComplexToComplexBufferAssembler;
 import io.github.dsheirer.sample.decimator.ComplexDecimator;
 import org.apache.commons.lang3.Validate;
 
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
-public class ComplexPrimeCICDecimate implements Listener<ComplexBuffer>
+/**
+ * Non-Recursive Prime-Factor CIC Filter.
+ *
+ * Implements the CIC filter described in Understanding Digital Signal Processing, 3e, Lyons, on page 769.  This
+ * filter is comprised of multiple decimating stages each with a prime factor decimation rate.  Multiple stages are
+ * cascaded to achieve the overall decimation rate.
+ *
+ * This filter currently supports a maximum decimation rate of 2801.  Higher decimation rates can be added by
+ * adding additional prime factors to the PRIMES array.
+ */
+public class ComplexPrimeCICDecimate implements Listener<ReusableComplexBuffer>
 {
+//    private final static Logger mLog = LoggerFactory.getLogger(ComplexPrimeCICDecimate.class);
+
+    /**
+     * PRIME numbers to use for decimation stage sizing.  This list contains values that should
+     * support input sample rates up to 70 MHz with an output channel rate of at least 25 kHz.
+     */
     public static int[] PRIMES = {2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53,
         59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151,
         157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251,
         257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359,
         367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463,
         467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593,
-        599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691};
+        599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701,
+        709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827,
+        829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947, 953,
+        967, 971, 977, 983, 991, 997, 997, 1009, 1013, 1019, 1021, 1031, 1033, 1039, 1049, 1051,
+        1061, 1063, 1069, 1087, 1091, 1093, 1097, 1103, 1109, 1117, 1123, 1129, 1151, 1153, 1163,
+        1171, 1181, 1187, 1193, 1201, 1213, 1217, 1223, 1229, 1231, 1237, 1249, 1259, 1277, 1279,
+        1283, 1289, 1291, 1297, 1301, 1303, 1307, 1319, 1321, 1327, 1361, 1367, 1373, 1381, 1399,
+        1409, 1423, 1427, 1429, 1433, 1439, 1447, 1451, 1453, 1459, 1471, 1481, 1483, 1487, 1489,
+        1493, 1499, 1511, 1523, 1531, 1543, 1549, 1553, 1559, 1567, 1571, 1579, 1583, 1597, 1601,
+        1607, 1609, 1613, 1619, 1621, 1627, 1637, 1657, 1663, 1667, 1669, 1693, 1697, 1699, 1709,
+        1721, 1723, 1733, 1741, 1747, 1753, 1759, 1777, 1783, 1787, 1789, 1801, 1811, 1823, 1831,
+        1847, 1861, 1867, 1871, 1873, 1877, 1879, 1889, 1901, 1907, 1913, 1931, 1933, 1949, 1951,
+        1973, 1979, 1987, 1993, 1997, 1999, 2003, 2011, 2017, 2027, 2029, 2039, 2053, 2063, 2069,
+        2081, 2083, 2087, 2089, 2099, 2111, 2113, 2129, 2131, 2137, 2141, 2143, 2153, 2161, 2179,
+        2203, 2207, 2213, 2221, 2237, 2239, 2243, 2251, 2267, 2269, 2273, 2281, 2287, 2293, 2297,
+        2309, 2311, 2333, 2339, 2341, 2347, 2351, 2357, 2371, 2377, 2381, 2383, 2389, 2393, 2399,
+        2411, 2417, 2423, 2437, 2441, 2447, 2459, 2467, 2473, 2477, 2503, 2521, 2531, 2539, 2543,
+        2549, 2551, 2557, 2579, 2591, 2593, 2609, 2617, 2621, 2633, 2647, 2657, 2659, 2663, 2671,
+        2677, 2683, 2687, 2689, 2693, 2699, 2707, 2711, 2713, 2719, 2729, 2731, 2741, 2749, 2753,
+        2767, 2777, 2789, 2791, 2797, 2801
+    };
 
-    private ArrayList<DecimatingStage> mDecimatingStages =
-        new ArrayList<DecimatingStage>();
+    private static Map<Integer,float[]> sLowPassFilters = new HashMap();
+    private static Map<Integer,List<Integer>> sPrimeFactors = new HashMap();
 
+    private List<DecimatingStage> mDecimatingStages = new ArrayList<DecimatingStage>();
     private DecimatingStage mFirstDecimatingStage;
-
     private Output mOutput;
 
     /**
-     * Non-Recursive Prime-Factor CIC Filter with float sample array inputs and
-     * decimated, single paired i/q float sample output.
+     * Constructs a new decimation filter.
      *
-     * Implements the CIC filter described in Understanding Digital Signal
-     * Processing, 3e, Lyons, on page 769.  This filter is comprised of multiple
-     * decimating stages each with a prime factor decimation rate.  Multiple
-     * stages are cascaded to achieve the overall decimation rate.
+     * An example setup for a 2.4 MHz input sample rate and 25 kHz output channel rate with a desired 12.5 kHz channel
+     * pass band might be:
+     * sampleRate = 2,400,000.0
+     * decimation = 96
+     * passFrequency = 6250 (1/4 of the channel rate)
+     * stopFrequency = 7000
      *
-     * This filter supports a maximum decimation rate of 700.  This filter can
-     * be adapted to higher decimation rates by adding additional prime factors
-     * to the PRIMES array.
+     * Note: the transition bandwidth (stop - start) directly impacts the size of the low-pass cleanup filter,
+     * where smaller transition bandwidth creates a longer filter that requires more processing effort.
      *
+     * @param sampleRate of the input sample stream
      * @param decimation - overall decimation rate
-     * @param order - filter order
+     * @param passFrequency for the final cleanup filter
+     * @param stopFrequency for the final cleanup filter
+     * @throws FilterDesignException if a final low-pass cleanup filter cannot be created for the output channel rate
+     *                               and specified pass/stop frequencies.
      */
-    public ComplexPrimeCICDecimate(int decimation, int order,
-                                   int passFrequency, int attenuation, Window.WindowType windowType)
+    public ComplexPrimeCICDecimate(double sampleRate, int decimation, double passFrequency, double stopFrequency)
+        throws FilterDesignException
     {
-        Validate.isTrue(decimation <= 700);
-
+        Validate.isTrue(decimation <= PRIMES[PRIMES.length - 1]);
 
         List<Integer> stageSizes = getPrimeFactors(decimation);
 
         for(int x = 0; x < stageSizes.size(); x++)
         {
-            DecimatingStage stage = new DecimatingStage(stageSizes.get(x), order);
+            DecimatingStage stage = new DecimatingStage(stageSizes.get(x), 1);
 
             mDecimatingStages.add(stage);
 
@@ -87,15 +124,16 @@ public class ComplexPrimeCICDecimate implements Listener<ComplexBuffer>
             }
             else
             {
-				/* Wire the current stage to the previous stage */
+                /* Wire the current stage to the previous stage */
                 mDecimatingStages.get(x - 1).setListener(stage);
             }
         }
 
-        mOutput = new Output(48000, passFrequency, attenuation, windowType);
+        double channelRate = sampleRate / (double)decimation;
 
-        mDecimatingStages.get(mDecimatingStages.size() - 1)
-            .setListener(mOutput);
+        mOutput = new Output(channelRate, passFrequency, stopFrequency);
+
+        mDecimatingStages.get(mDecimatingStages.size() - 1).setListener(mOutput);
     }
 
     public void dispose()
@@ -116,7 +154,7 @@ public class ComplexPrimeCICDecimate implements Listener<ComplexBuffer>
     /**
      * Adds a listener to receive the output of this CIC decimation filter
      */
-    public void setListener(Listener<ComplexBuffer> listener)
+    public void setListener(Listener<ReusableComplexBuffer> listener)
     {
         mOutput.setListener(listener);
     }
@@ -130,16 +168,26 @@ public class ComplexPrimeCICDecimate implements Listener<ComplexBuffer>
     }
 
     /**
-     * Calculates the prime factors of the decimation rate up to a maximum
-     * decimation rate of 700.  If you wish to have decimation rates higher
-     * than 700, then add additional prime factors to the PRIMES array.
+     * Calculates the prime factors of the decimation rate.  If you wish to have decimation rates higher than the
+     * highest rate listed in the PRIMES array, then add additional prime factors to the PRIMES array.
      *
      * @param decimation - integral decimation rate
      * @return - ordered list (smallest to largest) of prime factors
      */
     public static List<Integer> getPrimeFactors(int decimation)
     {
-        ArrayList<Integer> stages = new ArrayList<Integer>();
+        if(decimation > PRIMES[PRIMES.length - 1])
+        {
+            throw new IllegalArgumentException("Decimation rates higher than [" + PRIMES[PRIMES.length - 1] +
+                "] are not supported.  Update the PRIMES array to add support for higher decimation rates");
+        }
+
+        if(sPrimeFactors.containsKey(decimation))
+        {
+            return sPrimeFactors.get(decimation);
+        }
+
+        List<Integer> primeFactors = new ArrayList<Integer>();
 
         int pointer = 0;
 
@@ -149,8 +197,7 @@ public class ComplexPrimeCICDecimate implements Listener<ComplexBuffer>
 
             if(decimation % prime == 0)
             {
-                stages.add(prime);
-
+                primeFactors.add(prime);
                 decimation /= prime;
             }
             else
@@ -159,14 +206,16 @@ public class ComplexPrimeCICDecimate implements Listener<ComplexBuffer>
             }
         }
 
-        return stages;
+        sPrimeFactors.put(decimation, primeFactors);
+
+        return primeFactors;
     }
 
     /**
      * Primary input method for receiving sample arrays composed as I,Q,I,Q, etc.
      */
     @Override
-    public void receive(ComplexBuffer buffer)
+    public void receive(ReusableComplexBuffer buffer)
     {
         if(mFirstDecimatingStage != null)
         {
@@ -177,6 +226,8 @@ public class ComplexPrimeCICDecimate implements Listener<ComplexBuffer>
                 mFirstDecimatingStage.receive(samples[x], samples[x + 1]);
             }
         }
+
+        buffer.decrementUserCount();
     }
 
     /**
@@ -186,7 +237,7 @@ public class ComplexPrimeCICDecimate implements Listener<ComplexBuffer>
      */
     public class DecimatingStage implements ComplexSampleListener
     {
-        private ArrayList<Stage> mStages = new ArrayList<Stage>();
+        private List<Stage> mStages = new ArrayList<Stage>();
         private Stage mFirstStage;
         private ComplexDecimator mDecimator;
 
@@ -218,7 +269,6 @@ public class ComplexPrimeCICDecimate implements Listener<ComplexBuffer>
             }
 
             mDecimator = new ComplexDecimator(size);
-
             mStages.get(mStages.size() - 1).setListener(mDecimator);
         }
 
@@ -249,9 +299,8 @@ public class ComplexPrimeCICDecimate implements Listener<ComplexBuffer>
     }
 
     /**
-     * Single non-decimating CIC stage component.  Uses a circular buffer and a
-     * running average internally to implement the stage so that stage size has
-     * essentially no impact on the computational requirements of the stage
+     * Single non-decimating CIC stage component.  Uses a circular buffer and a running average internally to implement
+     * the stage so that stage size has essentially no impact on the computational requirements of the stage
      */
     public class Stage implements ComplexSampleListener
     {
@@ -268,7 +317,7 @@ public class ComplexPrimeCICDecimate implements Listener<ComplexBuffer>
 
         protected float mGain;
 
-        public Stage()
+        protected Stage()
         {
         }
 
@@ -279,7 +328,8 @@ public class ComplexPrimeCICDecimate implements Listener<ComplexBuffer>
             mISamples = new float[mSize];
             mQSamples = new float[mSize];
 
-            mGain = 1.0f / (float)size;
+            float baseGain = 1.0f / (float)size;
+            mGain = baseGain * (1.0f / (1.0f - baseGain));
         }
 
         public void dispose()
@@ -289,11 +339,11 @@ public class ComplexPrimeCICDecimate implements Listener<ComplexBuffer>
 
         public void receive(float i, float q)
         {
-			/* Subtract the oldest sample and add back in the newest */
+            /* Subtract the oldest sample and add in the newest sample */
             mISum = mISum - mISamples[mSamplePointer] + i;
             mQSum = mQSum - mQSamples[mSamplePointer] + q;
 
-			/* Overwrite the oldest sample with the newest */
+            /* Overwrite the oldest sample with the newest */
             mISamples[mSamplePointer] = i;
             mQSamples[mSamplePointer] = q;
 
@@ -317,30 +367,24 @@ public class ComplexPrimeCICDecimate implements Listener<ComplexBuffer>
     }
 
     /**
-     * Size 2 stage that removes the unnecessary circular buffer management for
-     * a two-stage.
+     * Size 2 stage that eliminates the unnecessary circular buffer management for a two-stage.
      */
     public class TwoStage extends Stage
     {
         public TwoStage()
         {
-            super();
-
             mGain = 0.5f;
         }
 
         public void receive(float i, float q)
         {
-            float iSum = mISum + i;
-            float qSum = mQSum + q;
+            if(mListener != null)
+            {
+                mListener.receive(((mISum + i) * mGain), ((mQSum + q) * mGain));
+            }
 
             mISum = i;
             mQSum = q;
-
-            if(mListener != null)
-            {
-                mListener.receive((iSum * mGain), (qSum * mGain));
-            }
         }
     }
 
@@ -351,62 +395,99 @@ public class ComplexPrimeCICDecimate implements Listener<ComplexBuffer>
      */
     public class Output implements ComplexSampleListener
     {
-        /* Decimated output buffers will contain 1024 samples */
-        private ComplexToComplexBufferAssembler mAssembler =
-            new ComplexToComplexBufferAssembler(2048);
+        /* Decimated output buffers will contain 1024 complex samples */
+        private ReusableComplexBufferAssembler mBufferAssembler;
+        private ComplexFIRFilter2 mLowPassFilter;
+        private Listener<ReusableComplexBuffer> mReusableComplexBufferListener;
 
-        private ComplexFIRFilter_CB_CB mCleanupFilter;
-        private HalfBandFilter_CB_CB mHalfBandFilter = new HalfBandFilter_CB_CB(
-            Filters.FIR_HALF_BAND_31T_ONE_EIGHTH_FCO.getCoefficients(), 0.4f, false);
-
-        public Output(int outputSampleRate, int passFrequency, int attenuation,
-                      Window.WindowType windowType)
+        public Output(double outputSampleRate, double passFrequency, double stopFrequency) throws FilterDesignException
         {
-            mCleanupFilter = new ComplexFIRFilter_CB_CB(FilterFactory
-                .getCICCleanupFilter(outputSampleRate,
-                    passFrequency,
-                    attenuation,
-                    windowType), 0.4f);
+            mBufferAssembler = new ReusableComplexBufferAssembler(2400, outputSampleRate);
 
-            //Bypassing the CIC cleanup filter for now
-            mAssembler.setListener(mHalfBandFilter);
+            //This may throw an exception if we can't design a filter for the sample rate and pass/stop frequencies
+            float[] filterCoefficients = getLowPassFilter(outputSampleRate, passFrequency, stopFrequency);
+            mLowPassFilter = new ComplexFIRFilter2(filterCoefficients, 1.0f);
 
-//			mAssembler.setListener( mCleanupFilter );
-//			mCleanupFilter.setListener( mHalfBandFilter );
+            mBufferAssembler.setListener(new Listener<ReusableComplexBuffer>()
+            {
+                @Override
+                public void receive(ReusableComplexBuffer reusableComplexBuffer)
+                {
+                    if(mReusableComplexBufferListener != null)
+                    {
+                        ReusableComplexBuffer filteredBuffer = mLowPassFilter.filter(reusableComplexBuffer);
+                        mReusableComplexBufferListener.receive(filteredBuffer);
+//                        mReusableComplexBufferListener.receive(reusableComplexBuffer);
+                    }
+                    else
+                    {
+                        reusableComplexBuffer.decrementUserCount();
+                    }
+                }
+            });
         }
 
         public void dispose()
         {
-            mAssembler.dispose();
-            mCleanupFilter.dispose();
-            mHalfBandFilter.dispose();
+            mBufferAssembler.dispose();
+            mLowPassFilter.dispose();
         }
 
         /**
-         * Receiver method for the output adapter to receive a filtered,
-         * decimated sample, apply gain correction, apply cleanup filtering
-         * and output the sample values as a complex sample.
+         * Interface for receiving CIC decimated output samples
          */
         @Override
         public void receive(float inphase, float quadrature)
         {
-            mAssembler.receive(inphase, quadrature);
+            mBufferAssembler.receive(inphase, quadrature);
         }
 
-        /**
-         * Adds a listener to receive output samples
-         */
-        public void setListener(Listener<ComplexBuffer> listener)
+        public void setListener(Listener<ReusableComplexBuffer> listener)
         {
-            mHalfBandFilter.setListener(listener);
+            mReusableComplexBufferListener = listener;
         }
 
-        /**
-         * Removes the listener from receiving output samples
-         */
         public void removeListener()
         {
-            mHalfBandFilter.removeListener();
+            mReusableComplexBufferListener = null;
+        }
+
+        /**
+         * Creates a low-pass filter to use as the final cleanup filter for the decimated output stream
+         *
+         * @param sampleRate for the final output channel rate
+         * @param passFrequency for half of the desired channel rate
+         * @param stopFrequency for the attenuated band
+         * @return a newly designed filter or a previously designed (cached) filter
+         * @throws FilterDesignException
+         */
+        private float[] getLowPassFilter(double sampleRate, double passFrequency, double stopFrequency) throws FilterDesignException
+        {
+            //Use existing filter if we've already designed one
+            if(sLowPassFilters.containsKey((int)sampleRate))
+            {
+                return sLowPassFilters.get((int)sampleRate);
+            }
+
+            FIRFilterSpecification specification = FIRFilterSpecification.lowPassBuilder()
+                .sampleRate(sampleRate)
+                .gridDensity(16)
+                .passBandCutoff(passFrequency)
+                .passBandAmplitude(1.0)
+                .passBandRipple(0.01)
+                .stopBandStart(stopFrequency)
+                .stopBandAmplitude(0.0)
+                .stopBandRipple(0.01)
+                .build();
+
+            RemezFIRFilterDesigner designer = new RemezFIRFilterDesigner(specification);
+
+            //This will throw an exception if the filter cannot be designed
+            float[] taps = designer.getImpulseResponse();
+
+            sLowPassFilters.put((int)sampleRate, taps);
+
+            return taps;
         }
     }
 }

src/main/java/io/github/dsheirer/dsp/filter/cic/RealPrimeCICDecimate.java

@@ -1,17 +1,17 @@
 /*******************************************************************************
  *     SDR Trunk 
  *     Copyright (C) 2015 Dennis Sheirer
- * 
+ *
  *     This program is free software: you can redistribute it and/or modify
  *     it under the terms of the GNU General Public License as published by
  *     the Free Software Foundation, either version 3 of the License, or
  *     (at your option) any later version.
- * 
+ *
  *     This program is distributed in the hope that it will be useful,
  *     but WITHOUT ANY WARRANTY; without even the implied warranty of
  *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  *     GNU General Public License for more details.
- * 
+ *
  *     You should have received a copy of the GNU General Public License
  *     along with this program.  If not, see <http://www.gnu.org/licenses/>
  ******************************************************************************/
@@ -20,13 +20,13 @@ package io.github.dsheirer.dsp.filter.cic;
 import io.github.dsheirer.dsp.filter.FilterFactory;
 import io.github.dsheirer.dsp.filter.Filters;
 import io.github.dsheirer.dsp.filter.Window.WindowType;
-import io.github.dsheirer.dsp.filter.fir.real.RealFIRFilter_RB_RB;
-import io.github.dsheirer.dsp.filter.halfband.real.HalfBandFilter_RB_RB;
+import io.github.dsheirer.dsp.filter.fir.real.RealFIRFilter2;
+import io.github.dsheirer.dsp.filter.halfband.real.HalfBandFilter;
 import io.github.dsheirer.sample.Listener;
+import io.github.dsheirer.sample.buffer.ReusableBufferAssembler;
+import io.github.dsheirer.sample.buffer.ReusableFloatBuffer;
 import io.github.dsheirer.sample.decimator.RealDecimator;
-import io.github.dsheirer.sample.real.RealBuffer;
 import io.github.dsheirer.sample.real.RealSampleListener;
-import io.github.dsheirer.sample.real.RealToRealBufferAssembler;
 import org.apache.commons.lang3.Validate;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -34,381 +34,389 @@ import org.slf4j.LoggerFactory;
 import java.util.ArrayList;
 import java.util.List;
 
-public class RealPrimeCICDecimate 
+public class RealPrimeCICDecimate
 {
-	private final static Logger mLog = 
-			LoggerFactory.getLogger( RealPrimeCICDecimate.class );
-	
-	public static int[] PRIMES = { 2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,
-		59,61,67,71,73,79,83,89,97,101,103,107,109,113,127,131,137,139,149,151,
-		157,163,167,173,179,181,191,193,197,199,211,223,227,229,233,239,241,251,
-		257,263,269,271,277,281,283,293,307,311,313,317,331,337,347,349,353,359,
-		367,373,379,383,389,397,401,409,419,421,431,433,439,443,449,457,461,463,
-		467,479,487,491,499,503,509,521,523,541,547,557,563,569,571,577,587,593,
-		599,601,607,613,617,619,631,641,643,647,653,659,661,673,677,683,691 };
-	
-	private ArrayList<DecimatingStage> mDecimatingStages = 
-				new ArrayList<DecimatingStage>();
-	
-	private DecimatingStage mFirstDecimatingStage;
+    private final static Logger mLog = LoggerFactory.getLogger(RealPrimeCICDecimate.class);
 
-	private Output mOutput;
-	
-	private int mOutputBufferSize = 2048;
+    public static int[] PRIMES = {2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53,
+        59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151,
+        157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251,
+        257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359,
+        367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463,
+        467, 479, 487, 491, 499, 503, 509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593,
+        599, 601, 607, 613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691};
 
-	/**
-	 * Non-Recursive Prime-Factor CIC Filter with float sample array inputs and
-	 * decimated float sample output.
-	 * 
-	 * Implements the CIC filter described in Understanding Digital Signal
-	 * Processing, 3e, Lyons, on page 769.  This filter is comprised of multiple
-	 * decimating stages each with a prime factor decimation rate.  Multiple 
-	 * stages are cascaded to achieve the overall decimation rate.
-	 * 
-	 * This filter supports a maximum decimation rate of 700.  This filter can
-	 * be adapted to higher decimation rates by adding additional prime factors
-	 * to the PRIMES array.
-	 * 
-	 * @param decimation - overall decimation rate
-	 * @param order - filter order
-	 */
-	public RealPrimeCICDecimate( int decimation, int order, int passFrequency, 
-			int attenuation, WindowType windowType )
-	{
-		this( decimation, order, passFrequency, attenuation, windowType, 2048 );
-	}
-	
-	public RealPrimeCICDecimate( int decimation, int order, int passFrequency, 
-			int attenuation, WindowType windowType, int outputBufferSize )
-	{
-		Validate.isTrue(decimation <= 700);
+    private List<DecimatingStage> mDecimatingStages = new ArrayList<DecimatingStage>();
+    private DecimatingStage mFirstDecimatingStage;
+    private Output mOutput;
 
-		mOutputBufferSize = outputBufferSize;
+    private int mOutputBufferSize = 2048;
 
-		List<Integer> stageSizes = getPrimeFactors( decimation );
-		
-		for( int x = 0; x < stageSizes.size(); x++ )
-		{
-			DecimatingStage stage = new DecimatingStage( stageSizes.get( x ), order );
-			
-			mDecimatingStages.add( stage );
-			
-			if( x == 0 )
-			{
-				/* Reference to first stage -- will receive all samples */
-				mFirstDecimatingStage = stage;
-			}
-			else
-			{
-				/* Wire the current stage to the previous stage */
-				mDecimatingStages.get( x - 1 ).setListener( stage );
-			}
-		}
-		
-		mOutput = new Output( 48000, passFrequency, attenuation, windowType, 
-				outputBufferSize );
-		
-		mDecimatingStages.get( mDecimatingStages.size() - 1 )
-							.setListener( mOutput );
-	}
-	
-	public void dispose()
-	{
-		for( DecimatingStage stage: mDecimatingStages )
-		{
-			stage.dispose();
-		}
-		
-		mDecimatingStages.clear();
-		mDecimatingStages = null;
-		mFirstDecimatingStage = null;
-		
-		mOutput.dispose();
-		mOutput = null;
-	}
-	
-	/**
-	 * Adds a listener to receive the output of this CIC decimation filter
-	 */
-	public void setListener( Listener<RealBuffer> listener )
-	{
-		mOutput.setListener( listener );
-	}
-	
-	/**
-	 * Removes listener from output of this CIC decimation filter
-	 */
-	public void removeListener()
-	{
-		mOutput.removeListener();
-	}
-
-	/**
-	 * Calculates the prime factors of the decimation rate up to a maximum 
-	 * decimation rate of 700.  If you wish to have decimation rates higher 
-	 * than 700, then add additional prime factors to the PRIMES array.
-	 * 
-	 * @param decimation - integral decimation rate
-	 * @return - ordered list (smallest to largest) of prime factors
-	 */
-	public static List<Integer> getPrimeFactors( int decimation )
-	{
-		ArrayList<Integer> stages = new ArrayList<Integer>();
-
-		int pointer = 0;
-		
-		while( decimation > 0 && pointer < PRIMES.length )
-		{
-			int prime = PRIMES[ pointer ];
-			
-			if( decimation % prime == 0 )
-			{
-				stages.add( prime );
-				
-				decimation /= prime;
-			}
-			else
-			{
-				pointer++;
-			}
-		}
-
-		return stages;
-	}
-
-	/**
-	 * Primary input method for receiving real buffers.
-	 */
-    public void receive( RealBuffer buffer )
+    /**
+     * Non-Recursive Prime-Factor CIC Filter with float sample array inputs and
+     * decimated float sample output.
+     *
+     * Implements the CIC filter described in Understanding Digital Signal
+     * Processing, 3e, Lyons, on page 769.  This filter is comprised of multiple
+     * decimating stages each with a prime factor decimation rate.  Multiple
+     * stages are cascaded to achieve the overall decimation rate.
+     *
+     * This filter supports a maximum decimation rate of 700.  This filter can
+     * be adapted to higher decimation rates by adding additional prime factors
+     * to the PRIMES array.
+     *
+     * @param decimation - overall decimation rate
+     * @param order - filter order
+     */
+    public RealPrimeCICDecimate(int decimation, int order, int passFrequency, int attenuation, WindowType windowType)
     {
-    	if( mFirstDecimatingStage != null )
-    	{
-    		for( float sample: buffer.getSamples() )
-    		{
-    			mFirstDecimatingStage.receive( sample );
-    		}
-    	}
+        this(decimation, order, passFrequency, attenuation, windowType, 2048);
     }
-	
-	/**
-	 * Decimating stage combines multiple CIC stages with a decimator.  The 
-	 * number of stages is indicated by the order value and the size indicates
-	 * the decimation rate of this stage.
-	 */
-	public class DecimatingStage implements RealSampleListener
-	{
-		private ArrayList<Stage> mStages = new ArrayList<Stage>();
-		private Stage mFirstStage;
-		private RealDecimator mDecimator;
-		
-		public DecimatingStage( int size, int order )
-		{
-			for( int x = 0; x < order; x++ )
-			{
-				Stage stage;
-				
-				if( size == 2 )
-				{
-					stage = new TwoStage();
-				}
-				else
-				{
-					stage = new Stage( size );
-				}
-				
-				mStages.add( stage );
-				
-				if( x == 0 )
-				{
-					mFirstStage = stage;
-				}
-				else
-				{
-					mStages.get( x - 1 ).setListener( stage );
-				}
-			}
-			
-			mDecimator = new RealDecimator( size );
-			
-			mStages.get( mStages.size() - 1 ).setListener( mDecimator );
-		}
-		
-		public void dispose()
-		{
-			for( Stage stage: mStages )
-			{
-				stage.dispose();
-			}
-			
-			mStages.clear();
-			mDecimator.dispose();
-			mDecimator = null;
-			mFirstStage = null;
-			mStages = null;
-		}
 
-		@Override
-        public void receive( float sample )
+    public RealPrimeCICDecimate(int decimation, int order, int passFrequency, int attenuation, WindowType windowType, int outputBufferSize)
+    {
+        Validate.isTrue(decimation <= 700);
+
+        mOutputBufferSize = outputBufferSize;
+
+        List<Integer> stageSizes = getPrimeFactors(decimation);
+
+        for(int x = 0; x < stageSizes.size(); x++)
         {
-			mFirstStage.receive( sample );
-        }
-		
-		public void setListener( RealSampleListener listener )
-		{
-			mDecimator.setListener( listener );
-		}
-	}
-	
-	/**
-	 * Single non-decimating CIC stage component.  Uses a circular buffer and a
-	 * running average internally to implement the stage so that stage size has 
-	 * essentially no impact on the computational requirements of the stage 
-	 */
-	public class Stage implements RealSampleListener
-	{
-		protected RealSampleListener mListener;
-		
-		private float[] mSamples;
-		
-		protected float mSum;
-		
-		private int mSamplePointer = 0;
-		private int mSize;
-	
-		protected float mGain;
-		
-		public Stage()
-		{
-		}
+            DecimatingStage stage = new DecimatingStage(stageSizes.get(x), order);
 
-		public Stage( int size )
-		{
-			mSize = size - 1;
-			
-			mSamples = new float[ mSize ];
-			
-			mGain = 1.0f / (float)size;
-		}
-		
-		public void dispose()
-		{
-			mListener = null;
-		}
-		
-		public void receive( float sample )
-		{
-			/* Subtract the oldest sample and add back in the newest */
-			mSum = mSum - mSamples[ mSamplePointer ] + sample;
+            mDecimatingStages.add(stage);
 
-			/* Overwrite the oldest sample with the newest */
-			mSamples[ mSamplePointer ] = sample;
-			
-			mSamplePointer++;
-			
-			if( mSamplePointer >= mSize )
-			{
-				mSamplePointer = 0;
-			}
-
-			if( mListener != null )
-			{
-				mListener.receive( mSum * mGain );
-			}
-		}
-		
-		public void setListener( RealSampleListener listener )
-		{
-			mListener = listener;
-		}
-	}
-	
-	/**
-	 * Size 2 stage that removes the unnecessary circular buffer management for
-	 * a two-stage.
-	 */
-	public class TwoStage extends Stage
-	{
-		public TwoStage()
-		{
-			super();
-			
-			mGain = 0.5f;
-		}
-		
-		public void receive( float sample )
-		{
-			float sum = mSum + sample;
-			
-			mSum = sample;
-			
-			if( mListener != null )
-			{
-				mListener.receive( sum * mGain );
-			}
-		}
-	}
-
-	/**
-	 * Output adapter - applies gain correction, applies cleanup filter, casts
-	 * double-valued samples into float-valued complex sample and sends the
-	 * result to the registered listener.
-	 */
-	public class Output implements RealSampleListener
-	{
-		/* Decimated output buffers will contain 1024 samples */
-		private RealToRealBufferAssembler mAssembler;
-
-		private RealFIRFilter_RB_RB mCleanupFilter;
-		private HalfBandFilter_RB_RB mHalfBandFilter = new HalfBandFilter_RB_RB(
-			Filters.FIR_HALF_BAND_31T_ONE_EIGHTH_FCO.getCoefficients(), 0.4f, false );
-
-		public Output( int outputSampleRate, int passFrequency, int attenuation, 
-				WindowType windowType, int outputBufferSize )
-		{
-			mCleanupFilter = new RealFIRFilter_RB_RB( FilterFactory
-					.getCICCleanupFilter( outputSampleRate, 
-										  passFrequency,
-										  attenuation,
-										  windowType ), 0.4f );
-			
-			mAssembler = new RealToRealBufferAssembler( outputBufferSize );
-			mAssembler.setListener( mCleanupFilter );
-			mCleanupFilter.setListener( mHalfBandFilter );
-			
-		}
-		
-		public void dispose()
-		{
-			mAssembler.dispose();
-			mCleanupFilter.dispose();
-			mHalfBandFilter.dispose();
-		}
-
-		/**
-		 * Receiver method for the output adapter to receive a filtered,
-		 * decimated sample, apply gain correction, apply cleanup filtering
-		 * and output the sample values as a complex sample.
-		 */
-		@Override
-        public void receive( float sample )
-        {
-			mAssembler.receive( sample * 32.0f );
-        }
-		
-		/**
-		 * Adds a listener to receive output samples
-		 */
-        public void setListener( Listener<RealBuffer> listener )
-        {
-			mHalfBandFilter.setListener( listener );
+            if(x == 0)
+            {
+                /* Reference to first stage -- will receive all samples */
+                mFirstDecimatingStage = stage;
+            }
+            else
+            {
+                /* Wire the current stage to the previous stage */
+                mDecimatingStages.get(x - 1).setListener(stage);
+            }
         }
 
-		/**
-		 * Removes the listener from receiving output samples
-		 */
+        mOutput = new Output(48000, passFrequency, attenuation, windowType,
+            outputBufferSize);
+
+        mDecimatingStages.get(mDecimatingStages.size() - 1)
+            .setListener(mOutput);
+    }
+
+    public void dispose()
+    {
+        for(DecimatingStage stage : mDecimatingStages)
+        {
+            stage.dispose();
+        }
+
+        mDecimatingStages.clear();
+        mDecimatingStages = null;
+        mFirstDecimatingStage = null;
+
+        mOutput.dispose();
+        mOutput = null;
+    }
+
+    /**
+     * Adds a listener to receive the output of this CIC decimation filter
+     */
+    public void setListener(Listener<ReusableFloatBuffer> listener)
+    {
+        mOutput.setListener(listener);
+    }
+
+    /**
+     * Removes listener from output of this CIC decimation filter
+     */
+    public void removeListener()
+    {
+        mOutput.removeListener();
+    }
+
+    /**
+     * Calculates the prime factors of the decimation rate up to a maximum
+     * decimation rate of 700.  If you wish to have decimation rates higher
+     * than 700, then add additional prime factors to the PRIMES array.
+     *
+     * @param decimation - integral decimation rate
+     * @return - ordered list (smallest to largest) of prime factors
+     */
+    public static List<Integer> getPrimeFactors(int decimation)
+    {
+        ArrayList<Integer> stages = new ArrayList<Integer>();
+
+        int pointer = 0;
+
+        while(decimation > 0 && pointer < PRIMES.length)
+        {
+            int prime = PRIMES[pointer];
+
+            if(decimation % prime == 0)
+            {
+                stages.add(prime);
+
+                decimation /= prime;
+            }
+            else
+            {
+                pointer++;
+            }
+        }
+
+        return stages;
+    }
+
+    /**
+     * Primary input method for receiving real buffers.
+     */
+    public void receive(ReusableFloatBuffer buffer)
+    {
+        if(mFirstDecimatingStage != null)
+        {
+            for(float sample : buffer.getSamples())
+            {
+                mFirstDecimatingStage.receive(sample);
+            }
+        }
+
+        buffer.decrementUserCount();
+    }
+
+    /**
+     * Decimating stage combines multiple CIC stages with a decimator.  The
+     * number of stages is indicated by the order value and the size indicates
+     * the decimation rate of this stage.
+     */
+    public class DecimatingStage implements RealSampleListener
+    {
+        private ArrayList<Stage> mStages = new ArrayList<Stage>();
+        private Stage mFirstStage;
+        private RealDecimator mDecimator;
+
+        public DecimatingStage(int size, int order)
+        {
+            for(int x = 0; x < order; x++)
+            {
+                Stage stage;
+
+                if(size == 2)
+                {
+                    stage = new TwoStage();
+                }
+                else
+                {
+                    stage = new Stage(size);
+                }
+
+                mStages.add(stage);
+
+                if(x == 0)
+                {
+                    mFirstStage = stage;
+                }
+                else
+                {
+                    mStages.get(x - 1).setListener(stage);
+                }
+            }
+
+            mDecimator = new RealDecimator(size);
+
+            mStages.get(mStages.size() - 1).setListener(mDecimator);
+        }
+
+        public void dispose()
+        {
+            for(Stage stage : mStages)
+            {
+                stage.dispose();
+            }
+
+            mStages.clear();
+            mDecimator.dispose();
+            mDecimator = null;
+            mFirstStage = null;
+            mStages = null;
+        }
+
+        @Override
+        public void receive(float sample)
+        {
+            mFirstStage.receive(sample);
+        }
+
+        public void setListener(RealSampleListener listener)
+        {
+            mDecimator.setListener(listener);
+        }
+    }
+
+    /**
+     * Single non-decimating CIC stage component.  Uses a circular buffer and a
+     * running average internally to implement the stage so that stage size has
+     * essentially no impact on the computational requirements of the stage
+     */
+    public class Stage implements RealSampleListener
+    {
+        protected RealSampleListener mListener;
+
+        private float[] mSamples;
+
+        protected float mSum;
+
+        private int mSamplePointer = 0;
+        private int mSize;
+
+        protected float mGain;
+
+        public Stage()
+        {
+        }
+
+        public Stage(int size)
+        {
+            mSize = size - 1;
+
+            mSamples = new float[mSize];
+
+            mGain = 1.0f / (float)size;
+        }
+
+        public void dispose()
+        {
+            mListener = null;
+        }
+
+        public void receive(float sample)
+        {
+            /* Subtract the oldest sample and add back in the newest */
+            mSum = mSum - mSamples[mSamplePointer] + sample;
+
+            /* Overwrite the oldest sample with the newest */
+            mSamples[mSamplePointer] = sample;
+
+            mSamplePointer++;
+
+            if(mSamplePointer >= mSize)
+            {
+                mSamplePointer = 0;
+            }
+
+            if(mListener != null)
+            {
+                mListener.receive(mSum * mGain);
+            }
+        }
+
+        public void setListener(RealSampleListener listener)
+        {
+            mListener = listener;
+        }
+    }
+
+    /**
+     * Size 2 stage that removes the unnecessary circular buffer management for
+     * a two-stage.
+     */
+    public class TwoStage extends Stage
+    {
+        public TwoStage()
+        {
+            super();
+
+            mGain = 0.5f;
+        }
+
+        public void receive(float sample)
+        {
+            float sum = mSum + sample;
+
+            mSum = sample;
+
+            if(mListener != null)
+            {
+                mListener.receive(sum * mGain);
+            }
+        }
+    }
+
+    /**
+     * Output adapter - applies gain correction, applies cleanup filter, casts
+     * double-valued samples into float-valued complex sample and sends the
+     * result to the registered listener.
+     */
+    public class Output implements RealSampleListener
+    {
+        /* Decimated output buffers will contain 1024 samples */
+        private ReusableBufferAssembler mAssembler;
+        private Listener<ReusableFloatBuffer> mReusableBufferListener;
+
+        private RealFIRFilter2 mCleanupFilter;
+        private HalfBandFilter mHalfBandFilter = new HalfBandFilter(
+            Filters.FIR_HALF_BAND_31T_ONE_EIGHTH_FCO.getCoefficients(), 0.4f, false);
+
+        public Output(int outputSampleRate, int passFrequency, int attenuation, WindowType windowType, int outputBufferSize)
+        {
+            mCleanupFilter = new RealFIRFilter2(FilterFactory.getCICCleanupFilter(outputSampleRate, passFrequency,
+                attenuation, windowType), 0.4f);
+
+            mAssembler = new ReusableBufferAssembler(outputBufferSize);
+            mAssembler.setListener(new Listener<ReusableFloatBuffer>()
+            {
+                @Override
+                public void receive(ReusableFloatBuffer reusableFloatBuffer)
+                {
+
+                    if(mReusableBufferListener != null)
+                    {
+                        ReusableFloatBuffer cleanupFiltered = mCleanupFilter.filter(reusableFloatBuffer);
+                        ReusableFloatBuffer halfBandFiltered = mHalfBandFilter.filter(cleanupFiltered);
+                        mReusableBufferListener.receive(halfBandFiltered);
+                    }
+                    else
+                    {
+                        reusableFloatBuffer.decrementUserCount();
+                    }
+                }
+            });
+        }
+
+        public void dispose()
+        {
+            mAssembler.dispose();
+            mCleanupFilter.dispose();
+            mHalfBandFilter.dispose();
+        }
+
+        /**
+         * Receiver method for the output adapter to receive a filtered,
+         * decimated sample, apply gain correction, apply cleanup filtering
+         * and output the sample values as a complex sample.
+         */
+        @Override
+        public void receive(float sample)
+        {
+            mAssembler.receive(sample * 32.0f);
+        }
+
+        /**
+         * Adds a listener to receive output samples
+         */
+        public void setListener(Listener<ReusableFloatBuffer> listener)
+        {
+            mReusableBufferListener = listener;
+        }
+
+        /**
+         * Removes the listener from receiving output samples
+         */
         public void removeListener()
         {
-			mHalfBandFilter.removeListener();
+            mReusableBufferListener = null;
         }
-	}
+    }
 }

src/main/java/io/github/dsheirer/dsp/filter/correction/IQCorrectionFilter.java

@@ -0,0 +1,58 @@
+/*******************************************************************************
+ * sdrtrunk
+ * Copyright (C) 2014-2017 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.filter.correction;
+
+import io.github.dsheirer.sample.buffer.ReusableComplexBuffer;
+import io.github.dsheirer.sample.buffer.ReusableComplexBufferQueue;
+
+public class IQCorrectionFilter
+{
+    private float mRatio = 0.00001f;
+    private float mAverageInphase = 0.0f;
+    private float mAverageQuadrature = 0.0f;
+    private ReusableComplexBufferQueue mReusableComplexBufferQueue = new ReusableComplexBufferQueue("IQCorrectionFilter");
+
+    public IQCorrectionFilter(float ratio)
+    {
+        mRatio = ratio;
+    }
+
+    public IQCorrectionFilter()
+    {
+    }
+
+    public ReusableComplexBuffer filter(ReusableComplexBuffer buffer)
+    {
+        float[] samples = buffer.getSamples();
+
+        ReusableComplexBuffer filtered = mReusableComplexBufferQueue.getBuffer(samples.length);
+        float[] filteredSamples = filtered.getSamples();
+
+        for(int x = 0; x < samples.length; x += 2)
+        {
+            mAverageInphase = mAverageInphase + (mRatio * (samples[x] - mAverageInphase));
+            filteredSamples[x] = samples[x] - mAverageInphase;
+
+            mAverageQuadrature = mAverageQuadrature + (mRatio * (samples[x + 1] - mAverageQuadrature));
+            filteredSamples[x + 1] = samples[x + 1] - mAverageQuadrature;
+        }
+
+        return filtered;
+    }
+}

src/main/java/io/github/dsheirer/dsp/filter/dc/BufferDCFilter.java

@@ -0,0 +1,98 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package io.github.dsheirer.dsp.filter.dc;
+
+import io.github.dsheirer.sample.buffer.ReusableBufferQueue;
+import io.github.dsheirer.sample.buffer.ReusableFloatBuffer;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class BufferDCFilter
+{
+    private final static Logger mLog = LoggerFactory.getLogger(BufferDCFilter.class);
+    private ReusableBufferQueue mReusableBufferQueue = new ReusableBufferQueue("Buffer DC Filter");
+    private double mAccumulator;
+
+    /**
+     * Calculates the DC offset present in the samples and subtracts the offset from all samples.
+     */
+    public void filterReal(float[] samples)
+    {
+        float adjustment = getOffset(samples);
+
+        for(int x = 0; x < samples.length; x++)
+        {
+            samples[x] = samples[x] - adjustment;
+        }
+    }
+
+    private float getOffset(float[] samples)
+    {
+        mAccumulator = 0.0;
+
+        for(int x = 0; x < samples.length; x++)
+        {
+            mAccumulator += samples[x];
+        }
+
+        return (float)(mAccumulator / (double)samples.length);
+    }
+
+    /**
+     * Calculates the DC offset present in the samples and subtracts the offset from all samples.
+     */
+    public static void filterComplex(float[] samples)
+    {
+        double iAccumulator = 0.0;
+        double qAccumulator = 0.0;
+
+        for(int x = 0; x < samples.length; x += 2)
+        {
+            iAccumulator += samples[x];
+            qAccumulator += samples[x + 1];
+        }
+
+        double half = (double)samples.length / 2.0;
+
+        float iAdjustment = (float)(iAccumulator / half);
+        float qAdjustment = (float)(qAccumulator / half);
+
+        for(int x = 0; x < samples.length; x += 2)
+        {
+            samples[x] = samples[x] - iAdjustment;
+            samples[x + 1] = samples[x + 1] - qAdjustment;
+        }
+    }
+
+    public ReusableFloatBuffer filter(ReusableFloatBuffer unfilteredBuffer)
+    {
+        float[] unfilteredSamples = unfilteredBuffer.getSamples();
+
+        ReusableFloatBuffer filteredBuffer = mReusableBufferQueue.getBuffer(unfilteredSamples.length);
+        float[] filteredSamples = filteredBuffer.getSamples();
+
+        float offset = getOffset(unfilteredSamples);
+
+        for(int x = 0; x < unfilteredSamples.length; x++)
+        {
+            filteredSamples[x] = unfilteredSamples[x] - offset;
+        }
+
+        unfilteredBuffer.decrementUserCount();
+
+        return filteredBuffer;
+    }
+}

src/main/java/io/github/dsheirer/dsp/filter/dc/DCRemovalFilter.java

@@ -1,41 +1,96 @@
 /*******************************************************************************
- *     SDR Trunk 
- *     Copyright (C) 2014,2015 Dennis Sheirer
- * 
- *     This program is free software: you can redistribute it and/or modify
- *     it under the terms of the GNU General Public License as published by
- *     the Free Software Foundation, either version 3 of the License, or
- *     (at your option) any later version.
- * 
- *     This program is distributed in the hope that it will be useful,
- *     but WITHOUT ANY WARRANTY; without even the implied warranty of
- *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *     GNU General Public License for more details.
- * 
- *     You should have received a copy of the GNU General Public License
- *     along with this program.  If not, see <http://www.gnu.org/licenses/>
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
  ******************************************************************************/
 package io.github.dsheirer.dsp.filter.dc;
 
+import io.github.dsheirer.sample.buffer.ReusableBufferQueue;
+import io.github.dsheirer.sample.buffer.ReusableFloatBuffer;
+
+/**
+ * DC removal filter for removing any DC offset that may be present when a signal is not aligned within the
+ * demodulated channel.
+ */
 public class DCRemovalFilter
 {
-	protected float mAverage;
-	protected float mRatio;
+    private ReusableBufferQueue mReusableBufferQueue = new ReusableBufferQueue("DC Removal Filter");
+    protected float mAverage;
+    protected float mRatio;
 
-	public DCRemovalFilter( float ratio )
-	{
-		mRatio = ratio;
-	}
+    /**
+     * Creates a DC removal filter.
+     *
+     * @param ratio
+     */
+    public DCRemovalFilter(float ratio)
+    {
+        mRatio = ratio;
+    }
 
-	public void reset()
-	{
-		mAverage = 0.0f;
-	}
+    /**
+     * Resets the running average to zero.
+     */
+    public void reset()
+    {
+        mAverage = 0.0f;
+    }
 
-	public float filter( float sample )
-	{
-		float filtered = sample - mAverage;
-		mAverage += mRatio * filtered;
-		return filtered;
-	}
+    /**
+     * Filters the sample and returns a filtered (ie DC-removed) sample.
+     * @param sample to filter
+     * @return filtered sample
+     */
+    public float filter(float sample)
+    {
+        float filtered = sample - mAverage;
+        mAverage += mRatio * filtered;
+        return filtered;
+    }
+
+    public float[] filter( float[] samples )
+    {
+        for( int x = 0; x < samples.length; x++ )
+        {
+            samples[ x ] = filter( samples[ x ] );
+        }
+
+        return samples;
+    }
+
+    /**
+     * Filters the buffer samples and returns a new reusable buffer with the filtered samples.
+     *
+     * Note: this method automatically manages the user accounting between the buffer argument and the new returned
+     * filtered sample buffer.
+     *
+     * @param unfilteredBuffer containing samples to filter
+     * @return a new reusable buffer containing the filtered samples with the user count set to 1.
+     */
+    public ReusableFloatBuffer filter(ReusableFloatBuffer unfilteredBuffer)
+    {
+        ReusableFloatBuffer filteredBuffer = mReusableBufferQueue.getBuffer(unfilteredBuffer.getSampleCount());
+
+        float[] unfilteredSamples = unfilteredBuffer.getSamples();
+        float[] filteredSamples = filteredBuffer.getSamples();
+
+        for(int x = 0; x < unfilteredSamples.length; x++)
+        {
+            filteredSamples[x] = filter(unfilteredSamples[x]);
+        }
+
+        unfilteredBuffer.decrementUserCount();
+
+        return filteredBuffer;
+    }
 }

src/main/java/io/github/dsheirer/dsp/filter/dc/DCRemovalFilter_CB.java

@@ -1,71 +0,0 @@
-/*******************************************************************************
- *     SDR Trunk 
- *     Copyright (C) 2014 Dennis Sheirer
- * 
- *     This program is free software: you can redistribute it and/or modify
- *     it under the terms of the GNU General Public License as published by
- *     the Free Software Foundation, either version 3 of the License, or
- *     (at your option) any later version.
- * 
- *     This program is distributed in the hope that it will be useful,
- *     but WITHOUT ANY WARRANTY; without even the implied warranty of
- *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *     GNU General Public License for more details.
- * 
- *     You should have received a copy of the GNU General Public License
- *     along with this program.  If not, see <http://www.gnu.org/licenses/>
- ******************************************************************************/
-package io.github.dsheirer.dsp.filter.dc;
-
-import io.github.dsheirer.sample.Listener;
-import io.github.dsheirer.sample.complex.ComplexBuffer;
-
-public class DCRemovalFilter_CB implements Listener<ComplexBuffer>
-{
-	private Listener<ComplexBuffer> mListener;
-	private DCRemovalFilter mIFilter;
-	private DCRemovalFilter mQFilter;
-	
-	public DCRemovalFilter_CB( float ratio )
-	{
-		mIFilter = new DCRemovalFilter( ratio );
-		mQFilter = new DCRemovalFilter( ratio );
-	}
-	
-	public void dispose()
-	{
-		mListener = null;
-	}
-	
-	public float[] filter( float[] samples )
-	{
-		for( int x = 0; x < samples.length; x += 2 )
-		{
-			samples[ x ] = mIFilter.filter( samples[ x ] );
-			samples[ x + 1 ] = mQFilter.filter( samples[ x + 1 ] );
-		}
-
-		return samples;
-	}
-	
-	public ComplexBuffer filter( ComplexBuffer buffer )
-	{
-		filter( buffer.getSamples() );
-		
-		return buffer;
-	}
-	
-	@Override
-	public void receive( ComplexBuffer buffer )
-	{
-		if( mListener != null )
-		{
-			mListener.receive( filter( buffer ) );
-		}
-	}
-	
-	public void setListener( Listener<ComplexBuffer> listener )
-	{
-		mListener = listener;
-	}
-}

src/main/java/io/github/dsheirer/dsp/filter/dc/DCRemovalFilter_RB.java

@@ -1,61 +0,0 @@
-package io.github.dsheirer.dsp.filter.dc;
-
-import io.github.dsheirer.sample.Listener;
-import io.github.dsheirer.sample.real.RealBuffer;
-
-public class DCRemovalFilter_RB extends DCRemovalFilter 
-					implements Listener<RealBuffer>
-{
-	protected Listener<RealBuffer> mListener;
-	
-	public DCRemovalFilter_RB( float ratio )
-	{
-		super( ratio );
-	}
-	
-	public void setListener( Listener<RealBuffer> listener )
-	{
-		mListener = listener;
-	}
-	
-	public void removeListener()
-	{
-		mListener = null;
-	}
-	
-	public void dispose()
-	{
-		mListener = null;
-	}
-	
-	public float[] filter( float[] samples )
-	{
-		for( int x = 0; x < samples.length; x++ )
-		{
-			samples[ x ] = filter( samples[ x ] );
-		}
-		
-		return samples;
-	}
-	
-	public RealBuffer filter( RealBuffer buffer )
-	{
-		float[] samples = buffer.getSamples();
-		
-		for( int x = 0; x < samples.length; x++ )
-		{
-			samples[ x ] = filter( samples[ x ] );
-		}
-
-		return buffer;
-	}
-
-	@Override
-	public void receive( RealBuffer buffer )
-	{
-		if( mListener != null )
-		{
-			mListener.receive( filter( buffer ) );
-		}
-	}
-}

src/main/java/io/github/dsheirer/dsp/filter/dc/DCRemovalFilter_R_R.java

@@ -1,54 +0,0 @@
-/*******************************************************************************
- *     SDR Trunk 
- *     Copyright (C) 2014 Dennis Sheirer
- * 
- *     This program is free software: you can redistribute it and/or modify
- *     it under the terms of the GNU General Public License as published by
- *     the Free Software Foundation, either version 3 of the License, or
- *     (at your option) any later version.
- * 
- *     This program is distributed in the hope that it will be useful,
- *     but WITHOUT ANY WARRANTY; without even the implied warranty of
- *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *     GNU General Public License for more details.
- * 
- *     You should have received a copy of the GNU General Public License
- *     along with this program.  If not, see <http://www.gnu.org/licenses/>
- ******************************************************************************/
-package io.github.dsheirer.dsp.filter.dc;
-
-import io.github.dsheirer.sample.real.RealSampleListener;
-
-public class DCRemovalFilter_R_R extends DCRemovalFilter implements RealSampleListener
-{
-	RealSampleListener mListener;
-	
-	public DCRemovalFilter_R_R( float ratio )
-	{
-		super( ratio );
-	}
-	
-	public void dispose()
-	{
-		mListener = null;
-	}
-
-	@Override
-    public void receive( float sample )
-    {
-		if( mListener != null )
-		{
-			mListener.receive( filter( sample ) );
-		}
-    }
-
-    public void setListener( RealSampleListener listener )
-    {
-		mListener = listener;
-    }
-    
-    public void removeListener()
-    {
-    	mListener = null;
-    }
-}

src/main/java/io/github/dsheirer/dsp/filter/dc/DCRemovalFilter_RealBuffer.java

@@ -1,60 +0,0 @@
-package io.github.dsheirer.dsp.filter.dc;
-
-import io.github.dsheirer.sample.Listener;
-import io.github.dsheirer.sample.real.RealBuffer;
-
-public class DCRemovalFilter_RealBuffer implements Listener<RealBuffer>
-{
-	private Listener<RealBuffer> mListener;
-	/**
-	 * Removes DC bias present across the samples in the buffer by calculating
-	 * the mean DC component and subtracting that component from each of the 
-	 * samples.
-	 */
-	public DCRemovalFilter_RealBuffer()
-	{
-	}
-	
-	public void dispose()
-	{
-		mListener = null;
-	}
-	
-	public RealBuffer filter( RealBuffer buffer )
-	{
-		double accumulator = 0.0d;
-		
-		for( float sample: buffer.getSamples() )
-		{
-			accumulator += sample;
-		}
-
-		float mean = (float)( accumulator / (double)buffer.getSamples().length );
-
-		for( float sample: buffer.getSamples() )
-		{
-			sample -= mean;
-		}
-		
-		return buffer;
-	}
-
-	@Override
-	public void receive( RealBuffer buffer )
-	{
-		if( mListener != null )
-		{
-			mListener.receive( filter( buffer ) );
-		}
-	}
-	
-	public void setListener( Listener<RealBuffer> listener )
-	{
-		mListener = listener;
-	}
-	
-	public void removeListener()
-	{
-		mListener = null;
-	}
-}

src/main/java/io/github/dsheirer/dsp/filter/dc/IIRSinglePoleDCRemovalFilter.java

@@ -1,45 +1,105 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
 package io.github.dsheirer.dsp.filter.dc;
 
+import io.github.dsheirer.sample.buffer.ReusableBufferQueue;
+import io.github.dsheirer.sample.buffer.ReusableFloatBuffer;
 import io.github.dsheirer.sample.real.RealSampleListener;
 
 public class IIRSinglePoleDCRemovalFilter implements RealSampleListener
 {
-	private float mAlpha;
-	private float mPreviousInput = 0.0f;
-	private float mPreviousOutput = 0.0f;
+    private ReusableBufferQueue mReusableBufferQueue = new ReusableBufferQueue("IIR DC Filter");
+    private float mAlpha;
+    private float mPreviousInput = 0.0f;
+    private float mPreviousOutput = 0.0f;
+    private float mCurrentOutput = 0.0f;
 
-	private RealSampleListener mListener;
-	
-	/**
-	 * IIR single-pole DC removal filter, as described by J M de Freitas in
-	 * 29Jan2007 paper at: 
-	 * 
-	 * http://www.mathworks.com/matlabcentral/fileexchange/downloads/72134/download
-	 * 
-	 * @param alpha 0.0 - 1.0 float - the closer alpha is to unity, the closer
-	 * the cutoff frequency is to DC.
-	 */
-	public IIRSinglePoleDCRemovalFilter( float alpha )
-	{
-		mAlpha = alpha;
-	}
-	@Override
-    public void receive( float currentInput )
+    private RealSampleListener mListener;
+
+    /**
+     * IIR single-pole DC removal filter, as described by J M de Freitas in
+     * 29Jan2007 paper at:
+     *
+     * http://www.mathworks.com/matlabcentral/fileexchange/downloads/72134/download
+     *
+     * @param alpha 0.0 - 1.0 float - the closer alpha is to unity, the closer
+     * the cutoff frequency is to DC.
+     */
+    public IIRSinglePoleDCRemovalFilter(float alpha)
     {
-		float currentOutput = ( currentInput - mPreviousInput ) + 
-							  ( mAlpha * mPreviousOutput );
-		
-		if( mListener != null )
-		{
-			mListener.receive( currentOutput );
-		}
-		
-		mPreviousInput = currentInput;
-		mPreviousOutput = currentOutput;
+        mAlpha = alpha;
     }
 
-	public void setListener( RealSampleListener listener )
-	{
-		mListener = listener;
-	}
+    /**
+     * Filters the sample
+     * @param sample to filter
+     * @return filtered output sample
+     */
+    public float filter(float sample)
+    {
+        mCurrentOutput = (sample - mPreviousInput) + (mAlpha * mPreviousOutput);
+
+        mPreviousInput = sample;
+        mPreviousOutput = mCurrentOutput;
+
+        return mCurrentOutput;
+    }
+
+    /**
+     * Filters the input buffer and returns a new filtered output buffer.
+     *
+     * Buffer user accounting is handled by this method where the input buffer user count is decremented and the
+     * returned output buffer has the user count incremented to one.
+     *
+     * @param inputBuffer to filter
+     * @return filtered samples in a new (ie reused) output buffer
+     */
+    public ReusableFloatBuffer filter(ReusableFloatBuffer inputBuffer)
+    {
+        ReusableFloatBuffer outputBuffer = mReusableBufferQueue.getBuffer(inputBuffer.getSampleCount());
+        float[] inputSamples = inputBuffer.getSamples();
+        float[] outputSamples = outputBuffer.getSamples();
+
+        for(int x = 0; x < inputSamples.length; x++)
+        {
+            outputSamples[x] = filter(inputSamples[x]);
+        }
+
+        inputBuffer.decrementUserCount();
+
+        return outputBuffer;
+    }
+
+    /**
+     * Implements the RealSampleListener interface for single sample streams.
+     */
+    @Override
+    public void receive(float sample)
+    {
+        if(mListener != null)
+        {
+            mListener.receive(filter(sample));
+        }
+    }
+
+    /**
+     * Assigns the listener to receive filtered samples processed by the RealSampleListener interface
+     */
+    public void setListener(RealSampleListener listener)
+    {
+        mListener = listener;
+    }
 }

src/main/java/io/github/dsheirer/dsp/filter/dc/IIRSinglePoleDCRemovalFilter_RB.java

@@ -1,69 +0,0 @@
-package io.github.dsheirer.dsp.filter.dc;
-
-import io.github.dsheirer.sample.Listener;
-import io.github.dsheirer.sample.real.RealBuffer;
-
-public class IIRSinglePoleDCRemovalFilter_RB implements Listener<RealBuffer>
-{
-	private float mAlpha;
-	private float mPreviousInput = 0.0f;
-	private float mPreviousOutput = 0.0f;
-	private Listener<RealBuffer> mListener;
-
-	/**
-	 * IIR single-pole DC removal filter, as described by J M de Freitas in
-	 * 29Jan2007 paper at: 
-	 * 
-	 * http://www.mathworks.com/matlabcentral/fileexchange/downloads/72134/download
-	 * 
-	 * @param alpha 0.0 - 1.0 float - the closer alpha is to unity, the closer
-	 * the cutoff frequency is to DC.
-	 */
-	public IIRSinglePoleDCRemovalFilter_RB( float alpha )
-	{
-		mAlpha = alpha;
-	}
-	
-	@Override
-	public void receive( RealBuffer buffer )
-	{
-		if( mListener != null )
-		{
-			mListener.receive( filter( buffer ) );
-		}
-	}
-	
-	public RealBuffer filter( RealBuffer buffer )
-	{
-		float[] samples = buffer.getSamples();
-		
-		for( int x = 0; x < samples.length; x++ )
-		{
-			samples[ x ] = filter( samples[ x ] );
-		}
-
-		return buffer;
-	}
-
-    public float filter( float sample )
-    {
-		float currentOutput = ( sample - mPreviousInput ) + 
-							  ( mAlpha * mPreviousOutput );
-		
-		mPreviousInput = sample;
-		mPreviousOutput = currentOutput;
-		
-		return currentOutput;
-    }
-
-	public void reset()
-	{
-		mPreviousInput = 0.0f;
-		mPreviousOutput = 0.0f;
-	}
-	
-	public void setListener( Listener<RealBuffer> listener )
-	{
-		mListener = listener;
-	}
-}

src/main/java/io/github/dsheirer/dsp/filter/design/FilterView.java

@@ -1,3 +1,18 @@
+/*******************************************************************************
+ * sdr-trunk
+ * Copyright (C) 2014-2018 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
+ * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License  along with this program.
+ * If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
 package io.github.dsheirer.dsp.filter.design;
 
 import io.github.dsheirer.gui.control.CurveFittedAreaChart;
@@ -58,16 +73,6 @@ public class FilterView extends BorderPane
         mImpulseChart.setAlternativeColumnFillVisible(false);
         mImpulseChart.setAlternativeRowFillVisible(false);
 
-        URL cssURL = FilterView.class.getResource("FilterView.css");
-
-        String css = null;
-
-        if(cssURL != null)
-        {
-            css = cssURL.toExternalForm();
-
-        }
-
         hbox.getChildren().add(mImpulseChart);
         HBox.setHgrow(mImpulseChart, Priority.ALWAYS);
 
@@ -81,8 +86,12 @@ public class FilterView extends BorderPane
         mDFTChart.setAlternativeColumnFillVisible(false);
         mDFTChart.setAlternativeRowFillVisible(false);
 
-        if(css != null)
+
+        URL url = getClass().getResource("/../resources/FilterView.css");
+
+        if(url != null)
         {
+            String css = url.toExternalForm();
             mImpulseChart.getStylesheets().add(css);
             mDFTChart.getStylesheets().add(css);
         }

src/main/java/io/github/dsheirer/dsp/filter/design/FilterViewer.java

@@ -40,52 +40,49 @@ public class FilterViewer extends Application
     private float[] getFilter()
     {
 //        FIRFilterSpecification specification = FIRFilterSpecification.lowPassBuilder()
-//            .sampleRate(48000)
+//            .sampleRate(8000)
 //            .gridDensity(16)
-//            .passBandCutoff(2500)
+//            .oddLength(true)
+//            .passBandCutoff(300)
 //            .passBandAmplitude(1.0)
 //            .passBandRipple(0.01)
-//            .stopBandStart(4000)
+//            .stopBandStart(500)
 //            .stopBandAmplitude(0.0)
-//            .stopBandRipple(0.008)
+//            .stopBandRipple(0.03) //Approximately 60 dB attenuation
 //            .build();
+//
+//        FIRFilterSpecification specification = FIRFilterSpecification.highPassBuilder()
+//            .sampleRate(8000)
+//            .stopBandCutoff(200)
+//            .stopBandAmplitude(0.0)
+//            .stopBandRipple(0.025)
+//            .passBandStart(300)
+//            .passBandAmplitude(1.0)
+//            .passBandRipple(0.01)
+//            .build();
+
         FIRFilterSpecification specification = FIRFilterSpecification.lowPassBuilder()
-            .sampleRate(48000)
-            .passBandCutoff(5100)
+            .sampleRate(50000.0)
+            .gridDensity(16)
+            .passBandCutoff(6000)
             .passBandAmplitude(1.0)
             .passBandRipple(0.01)
+            .stopBandStart(6700)
             .stopBandAmplitude(0.0)
-            .stopBandStart(6500)
             .stopBandRipple(0.01)
             .build();
 
-//        FIRFilterSpecification specification = FIRFilterSpecification.highPassBuilder()
-//            .sampleRate(24000)
-//            .stopBandCutoff(800)
-//            .stopBandAmplitude(0.0)
-//            .stopBandRipple(0.03)
-//            .passBandStart(1000)
-//            .passBandAmplitude(1.0)
-//            .passBandRipple(0.08)
-//            .build();
-
-//		FIRFilterSpecification specification = FIRFilterSpecification.bandPassBuilder()
-//	        .sampleRate( 48000 )
-//	        .stopFrequency1( 200 )
-//	        .passFrequencyBegin( 400 )
-//	        .passFrequencyEnd( 3200 )
-//	        .stopFrequency2( 3400 )
-//	        .stopRipple( 0.0003 )
-//	        .passRipple( 0.008)
-//	        .build();
-
         float[] taps = null;
 
-//        taps = FilterFactory.getSinc(6000, 1920, 47, Window.WindowType.BLACKMAN);
-
-//        taps = FilterFactory.getRootRaisedCosine(10, 10, 0.2f);
-//        taps = FilterFactory.getLowPass(48000, 6750, 7500, 60,
-//            Window.WindowType.HAMMING, true);
+//        try
+//        {
+//            taps = FilterFactory.getSincM2Synthesizer(12500.0, 2, 19);
+//            taps = FilterFactory.getSincFilter(25000.0, 12500.0, 2, 19, Window.WindowType.BLACKMAN_HARRIS_7, true);
+//        }
+//        catch(FilterDesignException fde)
+//        {
+//            mLog.error("Error");
+//        }
 
         try
         {
@@ -101,6 +98,11 @@ public class FilterViewer extends Application
             mLog.error("Filter design error", fde);
         }
 
+        if(taps == null)
+        {
+            throw new IllegalStateException("Couldn't design filter");
+        }
+
         return taps;
     }
 }

src/main/java/io/github/dsheirer/dsp/filter/fir/complex/ComplexFIRFilter.java

@@ -1,90 +0,0 @@
-/*******************************************************************************
- * sdr-trunk
- * Copyright (C) 2014-2018 Dennis Sheirer
- *
- * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
- * License as published by  the Free Software Foundation, either version 3 of the License, or  (at your option) any
- * later version.
- *
- * This program is distributed in the hope that it will be useful,  but WITHOUT ANY WARRANTY; without even the implied
- * warranty of  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License  along with this program.
- * If not, see <http://www.gnu.org/licenses/>
- *
- ******************************************************************************/
-package io.github.dsheirer.dsp.filter.fir.complex;
-
-import io.github.dsheirer.dsp.filter.fir.FIRFilter;
-import io.github.dsheirer.dsp.filter.fir.real.RealFIRFilter;
-import io.github.dsheirer.sample.complex.Complex;
-import io.github.dsheirer.sample.complex.ComplexBuffer;
-
-public class ComplexFIRFilter extends FIRFilter
-{
-    private RealFIRFilter mIFilter;
-    private RealFIRFilter mQFilter;
-
-    /**
-     * Complex FIR Filter for processing complex sample pairs.  Wraps two real
-     * FIR filters for processing each of the inphase and quadrature samples.
-     *
-     * @param coefficients - filter taps
-     * @param gain - gain to apply to filtered outputs - use 1.0f for no gain
-     */
-    public ComplexFIRFilter(float[] coefficients, float gain)
-    {
-        mIFilter = new RealFIRFilter(coefficients, gain);
-        mQFilter = new RealFIRFilter(coefficients, gain);
-    }
-
-    public float[] getCoefficients()
-    {
-        return mIFilter.getCoefficients();
-    }
-
-    public float filterInphase(float sample)
-    {
-        return mIFilter.filter(sample);
-    }
-
-    public float filterQuadrature(float sample)
-    {
-        return mQFilter.filter(sample);
-    }
-
-    public Complex filter(Complex sample)
-    {
-        float i = filterInphase(sample.inphase());
-        float q = filterQuadrature(sample.quadrature());
-
-        return new Complex(i, q);
-    }
-
-    /**
-     * Filters the complex samples from the buffer and returns a new complex buffer with the filtered output
-     *
-     * @param buffer with complex samples to filter
-     * @return new buffer containing filtered complex samples
-     */
-    public ComplexBuffer filter(ComplexBuffer buffer)
-    {
-        float[] samples = buffer.getSamples();
-        float[] filtered = new float[samples.length];
-
-        for(int x = 0; x < samples.length; x += 2)
-        {
-            filtered[x] = filterInphase(samples[x]);
-            filtered[x + 1] = filterQuadrature(samples[x + 1]);
-        }
-
-        return new ComplexBuffer(filtered);
-    }
-
-    @Override
-    public void dispose()
-    {
-        mIFilter.dispose();
-        mQFilter.dispose();
-    }
-}