Merge pull request #225 from DSheirer/222-spectral-display-of-frequency-correction-offset

Frequency change event handling in the processing chain

src/audio/AudioManager.java

@@ -86,6 +86,9 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
         loadSettings();
     }
 
+    /**
+     * Loads the saved mixer configuration or a default configuration for audio playback.
+     */
     private void loadSettings()
     {
         MixerChannelConfiguration configuration = null;
@@ -132,6 +135,9 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
         }
     }
 
+    /**
+     * Creates a default audio playback configuration with a mono audio playback channel.
+     */
     private MixerChannelConfiguration getDefaultConfiguration()
     {
         /* Use the system default mixer and mono channel as default startup */
@@ -161,6 +167,9 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
         mAudioOutputConnections.clear();
     }
 
+    /**
+     * Primary ingest point for audio produced by all decoding channels, for distribution to audio playback devices.
+     */
     @Override
     public synchronized void receive(AudioPacket packet)
     {
@@ -176,11 +185,11 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
 
         for(AudioOutputConnection connection : mAudioOutputConnections)
         {
-            if(connection.isInactive() &&
+            if(connection.isInactive() && mChannelConnectionMap.containsKey(connection.getChannelMetadataID()))
-                mChannelConnectionMap.containsKey(connection.getChannelMetadataID()))
             {
                 mChannelConnectionMap.remove(connection.getChannelMetadataID());
                 connection.disconnect();
+                mAvailableConnectionCount++;
                 changed = true;
             }
         }
@@ -192,7 +201,7 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
     }
 
     /**
-     * Identifies the lowest priority channel connection
+     * Identifies the lowest priority channel connection where the a higher value indicates a lower priority.
      */
     private void updateLowestPriorityAssignment()
     {
@@ -201,19 +210,32 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
         for(AudioOutputConnection connection : mAudioOutputConnections)
         {
             if(connection.isConnected() &&
-                (mLowestPriorityConnection == null || mLowestPriorityConnection.getPriority() > connection.getPriority()))
+                (mLowestPriorityConnection == null || mLowestPriorityConnection.getPriority() < connection.getPriority()))
             {
                 mLowestPriorityConnection = connection;
             }
         }
     }
 
+    /**
+     * Configures audio playback to use the configuration specified in the entry argument.
+     *
+     * @param entry to use in configuring the audio playback setup.
+     * @throws AudioException if there is an error
+     */
     @Override
     public void setMixerChannelConfiguration(MixerChannelConfiguration entry) throws AudioException
     {
         setMixerChannelConfiguration(entry, true);
     }
 
+    /**
+     * Configures audio playback to use the configuration specified in the entry argument.
+     *
+     * @param entry to use in configuring the audio playback setup.
+     * @param saveSettings to save the audio playback configuration settings in the properties file.
+     * @throws AudioException if there is an error
+     */
     public void setMixerChannelConfiguration(MixerChannelConfiguration entry, boolean saveSettings) throws AudioException
     {
         if(entry != null && (entry.getMixerChannel() == MixerChannel.MONO || entry.getMixerChannel() == MixerChannel.STEREO))
@@ -266,9 +288,8 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
     }
 
     /**
-     * Clears all channel assignments and terminates all audio outputs in
+     * Clears all channel assignments and terminates all audio outputs in preparation for complete shutdown or change
-     * preparation for complete shutdown or change to another mixer/channel
+     * to another mixer/channel configuration
-     * configuration
      */
     private void disposeCurrentConfiguration()
     {
@@ -288,12 +309,18 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
         mLowestPriorityConnection = null;
     }
 
+    /**
+     * Current audio playback mixer channel configuration setting.
+     */
     @Override
     public MixerChannelConfiguration getMixerChannelConfiguration() throws AudioException
     {
         return mMixerChannelConfiguration;
     }
 
+    /**
+     * List of audio outputs available for the current mixer channel configuration
+     */
     @Override
     public List<AudioOutput> getAudioOutputs()
     {
@@ -311,12 +338,18 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
         return outputs;
     }
 
+    /**
+     * Adds an audio event listener to receive audio event notifications.
+     */
     @Override
     public void addControllerListener(Listener<AudioEvent> listener)
     {
         mControllerBroadcaster.addListener(listener);
     }
 
+    /**
+     * Removes an audio event listener from receiving audio event notifications.
+     */
     @Override
     public void removeControllerListener(Listener<AudioEvent> listener)
     {
@@ -324,16 +357,15 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
     }
 
     /**
-     * Returns an audio output connection for the packet if one is
+     * Returns an audio output connection for the packet if one is available, or overrides an existing lower priority
-     * available, or overrides an existing lower priority connection.
+     * connection. Returns null if no connection is available for the audio packet.
-     * Returns null if no connection is available for the audio packet.
      *
-     * @param packet from a source
+     * @param audioPacket from a decoding channel source
      * @return an audio output connection or null
      */
-    private AudioOutputConnection getConnection(AudioPacket packet)
+    private AudioOutputConnection getConnection(AudioPacket audioPacket)
     {
-        int channelMetadataID = packet.getMetadata().getMetadataID();
+        int channelMetadataID = audioPacket.getMetadata().getMetadataID();
 
         //Use an existing connection
         if(mChannelConnectionMap.containsKey(channelMetadataID))
@@ -341,37 +373,35 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
             return mChannelConnectionMap.get(channelMetadataID);
         }
 
-        //Connect to and use an available connection
+        //Connect to an unused, available connection
         if(mAvailableConnectionCount > 0)
         {
             for(AudioOutputConnection connection : mAudioOutputConnections)
             {
                 if(connection.isDisconnected())
                 {
-                    connection.connect(channelMetadataID);
+                    connection.connect(channelMetadataID, audioPacket.getMetadata().getAudioPriority());
                     mChannelConnectionMap.put(channelMetadataID, connection);
+                    mAvailableConnectionCount--;
                     return connection;
                 }
             }
         }
-        //Preempt an existing connection and connect it to this higher priority source
+        //Preempt an existing lower priority connection and connect when this is a higher priority packet
-        else //Check for a channel priority override
+        else
         {
-            int priority = packet.getMetadata().getAudioPriority();
+            int priority = audioPacket.getMetadata().getAudioPriority();
 
-            if(mLowestPriorityConnection != null &&
-                priority < mLowestPriorityConnection.getPriority())
-            {
             AudioOutputConnection connection = mLowestPriorityConnection;
 
+            if(connection != null && priority < connection.getPriority())
+            {
                 mChannelConnectionMap.remove(connection.getChannelMetadataID());
 
-                connection.connect(channelMetadataID);
+                connection.connect(channelMetadataID, priority);
 
                 mChannelConnectionMap.put(channelMetadataID, connection);
 
-                updateLowestPriorityAssignment();
-
                 return connection;
             }
         }
@@ -494,9 +524,11 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
          * Connects this assignment to the indicated source so that audio
          * packets from this source can be sent to the audio output
          */
-        public void connect(int source)
+        public void connect(int source, int priority)
         {
             mChannelMetadataID = source;
+            mPriority = priority;
+            updateLowestPriorityAssignment();
 
             mAudioOutput.updateTimestamp();
         }

src/channel/metadata/ChannelMetadataModel.java

@@ -32,7 +32,7 @@ import java.util.Map;
 
 public class ChannelMetadataModel extends AbstractTableModel implements Listener<MutableMetadataChangeEvent>
 {
-    private final DecimalFormat FREQUENCY_FORMATTER = new DecimalFormat( "#.0000" );
+    private final DecimalFormat FREQUENCY_FORMATTER = new DecimalFormat( "#.00000" );
 
     public static final int COLUMN_STATE = 0;
     public static final int COLUMN_DECODER = 1;

src/channel/state/ChannelState.java

@@ -36,14 +36,19 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import sample.Listener;
 import sample.real.IOverflowListener;
+import source.tuner.frequency.FrequencyChangeEvent;
+import source.tuner.frequency.IFrequencyChangeListener;
 
 import java.util.concurrent.RejectedExecutionException;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.TimeUnit;
 
+import static source.tuner.frequency.FrequencyChangeEvent.Event.NOTIFICATION_FREQUENCY_CHANGE;
+
 public class ChannelState extends Module implements ICallEventProvider, IDecoderStateEventListener,
-    IDecoderStateEventProvider, ISquelchStateProvider, IAttributeChangeRequestListener, IOverflowListener
+    IDecoderStateEventProvider, IFrequencyChangeListener, ISquelchStateProvider, IAttributeChangeRequestListener,
+    IOverflowListener
 {
     private final static Logger mLog = LoggerFactory.getLogger(ChannelState.class);
 
@@ -61,6 +66,7 @@ public class ChannelState extends Module implements ICallEventProvider, IDecoder
     private ChannelType mChannelType;
     private TrafficChannelManager mTrafficChannelEndListener;
     private CallEvent mTrafficChannelCallEvent;
+    private FrequencyChangeListener mFrequencyChangeListener;
 
     private boolean mSquelchLocked = false;
     private boolean mSelected = false;
@@ -189,6 +195,17 @@ public class ChannelState extends Module implements ICallEventProvider, IDecoder
         mStateMonitor = null;
     }
 
+    @Override
+    public Listener<FrequencyChangeEvent> getFrequencyChangeListener()
+    {
+        if(mFrequencyChangeListener == null)
+        {
+            mFrequencyChangeListener = new FrequencyChangeListener();
+        }
+
+        return mFrequencyChangeListener;
+    }
+
     private boolean isStandardChannel()
     {
         return mChannelType == ChannelType.STANDARD;
@@ -532,6 +549,23 @@ public class ChannelState extends Module implements ICallEventProvider, IDecoder
         broadcast(mTrafficChannelCallEvent);
     }
 
+    /**
+     * Listener to receive frequency change events and rebroadcast them to the decoder states
+     */
+    public class FrequencyChangeListener implements Listener<FrequencyChangeEvent>
+    {
+        @Override
+        public void receive(FrequencyChangeEvent frequencyChangeEvent)
+        {
+            if(frequencyChangeEvent.getEvent() == NOTIFICATION_FREQUENCY_CHANGE)
+            {
+                long frequency = frequencyChangeEvent.getValue().longValue();
+
+                broadcast(new DecoderStateEvent(this, Event.SOURCE_FREQUENCY, getState(), frequency));
+            }
+        }
+    }
+
     /**
      * DecoderStateEvent receiver wrapper
      */

src/controller/channel/Channel.java

@@ -1,6 +1,6 @@
 /*******************************************************************************
- *     SDR Trunk 
+ * sdrtrunk
- *     Copyright (C) 2014-2016 Dennis Sheirer
+ * 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
@@ -14,15 +14,11 @@
  *
  * 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 controller.channel;
 
-import javax.xml.bind.annotation.XmlAttribute;
+import controller.config.Configuration;
-import javax.xml.bind.annotation.XmlElement;
-import javax.xml.bind.annotation.XmlRootElement;
-import javax.xml.bind.annotation.XmlSeeAlso;
-import javax.xml.bind.annotation.XmlTransient;
-
 import module.decode.DecoderFactory;
 import module.decode.DecoderType;
 import module.decode.config.AuxDecodeConfiguration;
@@ -31,6 +27,7 @@ import module.log.EventLogType;
 import module.log.config.EventLogConfiguration;
 import record.RecorderType;
 import record.config.RecordConfiguration;
+import sample.Listener;
 import source.SourceType;
 import source.config.SourceConfigFactory;
 import source.config.SourceConfigRecording;
@@ -40,15 +37,24 @@ import source.tuner.TunerChannel;
 import source.tuner.TunerChannel.Type;
 import source.tuner.frequency.FrequencyChangeEvent;
 import source.tuner.frequency.FrequencyChangeEvent.Event;
-import source.tuner.frequency.IFrequencyChangeProcessor;
+
-import controller.config.Configuration;
+import javax.xml.bind.annotation.XmlAttribute;
+import javax.xml.bind.annotation.XmlElement;
+import javax.xml.bind.annotation.XmlRootElement;
+import javax.xml.bind.annotation.XmlSeeAlso;
+import javax.xml.bind.annotation.XmlTransient;
 
 @XmlSeeAlso({Configuration.class})
 @XmlRootElement(name = "channel")
-public class Channel extends Configuration implements IFrequencyChangeProcessor
+public class Channel extends Configuration implements Listener<FrequencyChangeEvent>
 {
     // Standard channels are persisted and traffic channels are temporary
-	public enum ChannelType { STANDARD, TRAFFIC };
+    public enum ChannelType
+    {
+        STANDARD, TRAFFIC
+    }
+
+    ;
 
 
     // Static unique channel identifier tracking
@@ -278,7 +284,7 @@ public class Channel extends Configuration implements IFrequencyChangeProcessor
      * Note: this method is package private and is intended to be managed
      * by a co-package central processing manager
      *
-	 * @see controller.ChannelProcessingManager
+     * @see controller.channel.ChannelProcessingManager
      */
     void setEnabled(boolean enabled)
     {
@@ -436,8 +442,7 @@ public class Channel extends Configuration implements IFrequencyChangeProcessor
     {
         TunerChannel tunerChannel = getTunerChannel();
 
-		return tunerChannel != null &&
+        return tunerChannel != null && tunerChannel.overlaps(minimum, maximum);
-			   tunerChannel.overlaps( minimum, maximum );
     }
 
     /**
@@ -447,7 +452,7 @@ public class Channel extends Configuration implements IFrequencyChangeProcessor
      * be used to visually show in the spectral display.
      */
     @Override
-	public void frequencyChanged( FrequencyChangeEvent event )
+    public void receive(FrequencyChangeEvent event)
     {
         if(event.getEvent() == Event.NOTIFICATION_CHANNEL_FREQUENCY_CORRECTION_CHANGE)
         {
@@ -455,9 +460,21 @@ public class Channel extends Configuration implements IFrequencyChangeProcessor
         }
     }
 
+    /**
+     * Current channel frequency correction value (when this channel is processing)
+     * @return
+     */
     @XmlTransient
     public int getChannelFrequencyCorrection()
     {
         return mChannelFrequencyCorrection;
     }
+
+    /**
+     * Resets frequency correction value to 0
+     */
+    public void resetFrequencyCorrection()
+    {
+        mChannelFrequencyCorrection = 0;
+    }
 }

src/controller/channel/ChannelProcessingManager.java

@@ -231,7 +231,7 @@ public class ChannelProcessingManager implements ChannelEventListener
 
         if(processingChain == null)
         {
-            processingChain = new ProcessingChain(channel.getName(), channel.getChannelType());
+            processingChain = new ProcessingChain(channel.getChannelType());
 
 			/* Register global listeners */
             for(Listener<AudioPacket> listener : mAudioPacketListeners)
@@ -244,6 +244,9 @@ public class ChannelProcessingManager implements ChannelEventListener
                 processingChain.addMessageListener(listener);
             }
 
+            //Register channel to receive frequency correction events to show in the spectral display (hack!)
+            processingChain.addFrequencyChangeListener(channel);
+
 			/* Processing Modules */
             List<Module> modules = DecoderFactory.getModules(mChannelModel, mChannelMapModel, this,
                 mAliasModel, channel, processingChain.getChannelState().getMutableMetadata());
@@ -347,6 +350,9 @@ public class ChannelProcessingManager implements ChannelEventListener
 
             processingChain.removeRecordingModules();
 
+            //Deregister channel from receive frequency correction events to show in the spectral display (hack!)
+            processingChain.removeFrequencyChangeListener(channel);
+            channel.resetFrequencyCorrection();
 
             mChannelModel.broadcast(new ChannelEvent(channel, Event.NOTIFICATION_PROCESSING_STOP));
 

src/dsp/filter/cic/ComplexPrimeCICDecimate.java

@@ -1,6 +1,6 @@
 /*******************************************************************************
- *     SDR Trunk 
+ * sdrtrunk
- *     Copyright (C) 2015 Dennis Sheirer
+ * 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
@@ -14,23 +14,24 @@
  *
  * 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 dsp.filter.cic;
 
-import java.util.ArrayList;
+import dsp.filter.FilterFactory;
-import java.util.List;
+import dsp.filter.Filters;
-
+import dsp.filter.Window.WindowType;
+import dsp.filter.fir.complex.ComplexFIRFilter_CB_CB;
+import dsp.filter.halfband.complex.HalfBandFilter_CB_CB;
 import org.apache.commons.lang3.Validate;
 import sample.Listener;
 import sample.complex.ComplexBuffer;
 import sample.complex.ComplexSampleListener;
 import sample.complex.ComplexToComplexBufferAssembler;
 import sample.decimator.ComplexDecimator;
-import dsp.filter.FilterFactory;
+
-import dsp.filter.Filters;
+import java.util.ArrayList;
-import dsp.filter.Window.WindowType;
+import java.util.List;
-import dsp.filter.fir.complex.ComplexFIRFilter_CB_CB;
-import dsp.filter.halfband.complex.HalfBandFilter_CB_CB;
 
 public class ComplexPrimeCICDecimate implements Listener<ComplexBuffer>
 {
@@ -367,8 +368,11 @@ public class ComplexPrimeCICDecimate implements Listener<ComplexBuffer>
                     attenuation,
                     windowType), 0.4f);
 
-			mAssembler.setListener( mCleanupFilter );
+            //Bypassing the CIC cleanup filter for now
-			mCleanupFilter.setListener( mHalfBandFilter );
+            mAssembler.setListener(mHalfBandFilter);
+
+//			mAssembler.setListener( mCleanupFilter );
+//			mCleanupFilter.setListener( mHalfBandFilter );
         }
 
         public void dispose()

src/instrument/InstrumentableProcessingChain.java

@@ -1,21 +1,38 @@
+/*******************************************************************************
+ * 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 instrument;
 
+import controller.channel.Channel.ChannelType;
 import instrument.tap.Tap;
 import instrument.tap.TapGroup;
-
-import java.util.ArrayList;
-import java.util.List;
-
 import module.Module;
 import module.ProcessingChain;
 import source.Source;
-import controller.channel.Channel.ChannelType;
+
+import java.util.ArrayList;
+import java.util.List;
 
 public class InstrumentableProcessingChain extends ProcessingChain implements Instrumentable
 {
     public InstrumentableProcessingChain()
     {
-		super( "instrumented", ChannelType.STANDARD );
+        super(ChannelType.STANDARD);
     }
 
     public void setSource(Source source) throws IllegalStateException

src/module/ProcessingChain.java

@@ -108,7 +108,6 @@ public class ProcessingChain implements IChannelEventListener
     private Broadcaster<RealBuffer> mUnFilteredRealBufferBroadcaster = new Broadcaster<>();
     private Broadcaster<SquelchState> mSquelchStateBroadcaster = new Broadcaster<>();
 
-    private String mName;
     private AtomicBoolean mRunning = new AtomicBoolean();
 
     protected Source mSource;
@@ -120,13 +119,10 @@ public class ProcessingChain implements IChannelEventListener
     /**
      * Creates a processing chain for managing a set of modules
      *
-     * @param name for thread pool naming each thread
      * @param channelType
      */
-    public ProcessingChain(String name, ChannelType channelType)
+    public ProcessingChain(ChannelType channelType)
     {
-        mName = name;
-
         mChannelState = new ChannelState(channelType);
         addModule(mChannelState);
 
@@ -211,6 +207,8 @@ public class ProcessingChain implements IChannelEventListener
         }
 
         mSource = source;
+
+        addModule(mSource);
     }
 
     /**
@@ -557,25 +555,6 @@ public class ProcessingChain implements IChannelEventListener
                             + "sample type - cannot start processing chain");
                 }
 				
-				/* If this is a tuner source, broadcast the frequency to all 
-				 * of the decoder state's and start the samples flowing */
-                if(mSource instanceof TunerChannelSource)
-                {
-                    TunerChannelSource tcs = (TunerChannelSource) mSource;
-
-                    try
-                    {
-                        long frequency = tcs.getFrequency();
-
-                        mDecoderStateEventBroadcaster.broadcast(
-                            new DecoderStateEvent(this, Event.SOURCE_FREQUENCY, State.IDLE, frequency));
-                    }
-                    catch(SourceException e)
-                    {
-                        mLog.error("Error getting frequency from tuner channel source", e);
-                    }
-                }
-
 				/* Start each of the modules */
                 for(Module module : mModules)
                 {
@@ -588,8 +567,6 @@ public class ProcessingChain implements IChannelEventListener
                         mLog.error("Error starting module", e);
                     }
                 }
-
-                mSource.start(ThreadPool.SCHEDULED);
             }
             else
             {
@@ -606,9 +583,16 @@ public class ProcessingChain implements IChannelEventListener
     {
         if(mRunning.compareAndSet(true, false))
         {
+			/* Stop each of the modules */
+            for(Module module : mModules)
+            {
+                module.stop();
+            }
+
             if(mSource != null)
             {
-                mSource.stop();
+                removeModule(mSource);
+
                 mSource.setOverflowListener(null);
 
                 switch(mSource.getSampleType())
@@ -629,11 +613,6 @@ public class ProcessingChain implements IChannelEventListener
                 mSource = null;
             }
 			
-			/* Stop each of the modules */
-            for(Module module : mModules)
-            {
-                module.stop();
-            }
         }
     }
 
@@ -760,6 +739,24 @@ public class ProcessingChain implements IChannelEventListener
         mMessageBroadcaster.removeListener(listener);
     }
 
+    /**
+     * Adds the listener to receive frequency change events from the processing chain
+     * @param listener to receive events
+     */
+    public void addFrequencyChangeListener(Listener<FrequencyChangeEvent> listener)
+    {
+        mFrequencyChangeEventBroadcaster.addListener(listener);
+    }
+
+    /**
+     * Removes the listener from receiving frequency change events
+     * @param listener to remove
+     */
+    public void removeFrequencyChangeListener(Listener<FrequencyChangeEvent> listener)
+    {
+        mFrequencyChangeEventBroadcaster.removeListener(listener);
+    }
+
     /**
      * Adds the listener to receive call events from all modules.
      */

src/module/decode/p25/C4FMSymbolFilter.java

@@ -9,19 +9,19 @@ import instrument.tap.stream.FloatTap;
 import java.util.ArrayList;
 import java.util.List;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import sample.Listener;
 import sample.real.RealBuffer;
 import sample.real.RealSampleListener;
 import sample.real.RealSampleProvider;
+import source.tuner.TunerChannelSource;
 import source.tuner.frequency.FrequencyChangeEvent;
 import source.tuner.frequency.FrequencyChangeEvent.Event;
 import source.tuner.frequency.IFrequencyChangeListener;
 import dsp.gain.DirectGainControl;
 
-public class C4FMSymbolFilter implements Listener<RealBuffer>, 
+public class C4FMSymbolFilter implements Listener<RealBuffer>, IFrequencyChangeListener, RealSampleProvider, Instrumentable
-										 IFrequencyChangeListener,
-										 RealSampleProvider,
-										 Instrumentable
 {
 	private static final float TAPS[][] =
 	{ 
@@ -198,8 +198,7 @@ public class C4FMSymbolFilter implements Listener<RealBuffer>,
 	
 	private RealSampleListener mListener;
 	
-	private DirectGainControl mGainController = 
+	private DirectGainControl mGainController = new DirectGainControl( 15.0f, 0.1f, 35.0f, 0.3f );
-			new DirectGainControl( 15.0f, 0.1f, 35.0f, 0.3f );
 
 	private int mFrequencyAdjustmentRequested = 0;
 	private int mFrequencyCorrection = 0;
@@ -258,8 +257,7 @@ public class C4FMSymbolFilter implements Listener<RealBuffer>,
 				correction = -mFrequencyCorrectionMaximum;
 			}
 
-			broadcast( new FrequencyChangeEvent( 
+			broadcast( new FrequencyChangeEvent(Event.REQUEST_CHANNEL_FREQUENCY_CORRECTION_CHANGE, correction ) );
-				Event.REQUEST_CHANNEL_FREQUENCY_CORRECTION_CHANGE, correction ) );
 
 			mFrequencyAdjustmentRequested = 0;
 		}
@@ -452,6 +450,10 @@ public class C4FMSymbolFilter implements Listener<RealBuffer>,
 		}
     }
 
+    /**
+     * Broadcasts a frequency change event to the registered listener
+     * @param event
+     */
 	public void broadcast( FrequencyChangeEvent event )
 	{
 		if( mFrequencyChangeListener != null )
@@ -460,6 +462,10 @@ public class C4FMSymbolFilter implements Listener<RealBuffer>,
 		}
 	}
 
+    /**
+     * Sets the listener for frequency change events.
+     * @param listener
+     */
 	public void setFrequencyChangeListener( Listener<FrequencyChangeEvent> listener )
 	{
 		mFrequencyChangeListener = listener;

src/module/decode/p25/P25Decoder.java

@@ -4,8 +4,10 @@ import alias.AliasList;
 import instrument.Instrumentable;
 import module.decode.Decoder;
 import module.decode.DecoderType;
+import source.tuner.frequency.IFrequencyChangeListener;
+import source.tuner.frequency.IFrequencyChangeProvider;
 
-public abstract class P25Decoder extends Decoder implements Instrumentable
+public abstract class P25Decoder extends Decoder implements IFrequencyChangeListener, IFrequencyChangeProvider, Instrumentable
 {
 	private P25MessageProcessor mMessageProcessor;
 	

src/module/decode/p25/P25MessageFramer.java

@@ -689,8 +689,7 @@ public class P25MessageFramer implements Listener<Dibit>
     	private LSMDemodulator mDemodulator;
     	private double mCorrection;
     	
-    	public CostasPhaseErrorDetector( FrameSync frameSync, 
+    	public CostasPhaseErrorDetector( FrameSync frameSync, LSMDemodulator demodulator, double correction )
-    			LSMDemodulator demodulator, double correction )
     	{
     		super( frameSync.getSync() );
 

src/module/decode/p25/P25_C4FMDecoder.java

@@ -1,6 +1,6 @@
 /*******************************************************************************
- *     SDR Trunk 
+ * sdrtrunk
- *     Copyright (C) 2014,2015 Dennis Sheirer
+ * 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
@@ -14,6 +14,7 @@
  *
  * 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 module.decode.p25;
 
@@ -41,8 +42,7 @@ import dsp.filter.FilterFactory;
 import dsp.filter.Window.WindowType;
 import dsp.filter.fir.real.RealFIRFilter_RB_RB;
 
-public class P25_C4FMDecoder extends P25Decoder 
+public class P25_C4FMDecoder extends P25Decoder implements IFilteredRealBufferListener
-	implements IFrequencyChangeListener, IFrequencyChangeProvider,IFilteredRealBufferListener
 {
 	private final static Logger mLog = LoggerFactory.getLogger( P25_C4FMDecoder.class );
 	

src/module/decode/p25/P25_LSMDecoder.java

@@ -42,6 +42,7 @@ import dsp.filter.fir.complex.ComplexFIRFilter_CB_CB;
 import dsp.gain.ComplexFeedForwardGainControl;
 import dsp.psk.LSMDemodulator;
 import dsp.psk.QPSKPolarSlicer;
+import source.tuner.frequency.FrequencyChangeEvent;
 
 public class P25_LSMDecoder extends P25Decoder implements IComplexBufferListener
 {
@@ -56,8 +57,7 @@ public class P25_LSMDecoder extends P25Decoder implements IComplexBufferListener
 	private List<TapGroup> mAvailableTaps;
 	
 	private ComplexFIRFilter_CB_CB mBasebandFilter;
-	private ComplexBufferToStreamConverter mStreamConverter = 
+	private ComplexBufferToStreamConverter mStreamConverter = new ComplexBufferToStreamConverter();
-							new ComplexBufferToStreamConverter();
 	private ComplexFeedForwardGainControl mAGC = 
 							new ComplexFeedForwardGainControl( 32 );
 	private LSMDemodulator mLSMDemodulator = new LSMDemodulator();
@@ -108,6 +108,29 @@ public class P25_LSMDecoder extends P25Decoder implements IComplexBufferListener
 		mMessageFramer = null;
 	}
 
+    @Override
+    public void setFrequencyChangeListener(Listener<FrequencyChangeEvent> listener)
+    {
+    }
+
+    @Override
+    public void removeFrequencyChangeListener()
+    {
+    }
+
+    @Override
+    public Listener<FrequencyChangeEvent> getFrequencyChangeListener()
+    {
+        return new Listener<FrequencyChangeEvent>()
+        {
+            @Override
+            public void receive(FrequencyChangeEvent frequencyChangeEvent)
+            {
+                //Ignored
+            }
+        };
+    }
+
     @Override
 	public Listener<ComplexBuffer> getComplexBufferListener()
 	{

src/sample/Broadcaster.java

@@ -58,6 +58,11 @@ public class Broadcaster<T> implements Listener<T>
 	
 	public void addListener( Listener<T> listener )
 	{
+	    if(listener == null)
+        {
+            throw new IllegalArgumentException("Listener cannot be null");
+        }
+
 		mListeners.add( listener );
 	}
 	

src/source/Source.java

@@ -20,11 +20,13 @@ package source;
 import module.Module;
 import sample.SampleType;
 import sample.real.IOverflowListener;
+import source.tuner.frequency.IFrequencyChangeListener;
+import source.tuner.frequency.IFrequencyChangeProvider;
 
 /**
  * Abstract class to define the minimum functionality of a sample data provider.
  */
-public abstract class Source extends Module
+public abstract class Source extends Module implements IFrequencyChangeListener, IFrequencyChangeProvider
 {
     protected SampleType mSampleType;
     protected IOverflowListener mOverflowListener;

src/source/mixer/RealMixerSource.java

@@ -36,11 +36,11 @@ import sample.real.RealBuffer;
 import source.RealSource;
 import source.SourceException;
 import dsp.gain.AutomaticGainControl;
+import source.tuner.frequency.FrequencyChangeEvent;
 
 public class RealMixerSource extends RealSource
 {
-	private final static Logger mLog = 
+	private final static Logger mLog = LoggerFactory.getLogger( RealMixerSource.class );
-			LoggerFactory.getLogger( RealMixerSource.class );
 
 	private long mFrequency = 0;
 	private int mBufferSize = 16384;
@@ -48,13 +48,11 @@ public class RealMixerSource extends RealSource
 	private BufferReader mBufferReader = new BufferReader();
 	private TargetDataLine mTargetDataLine;
 	private AudioFormat mAudioFormat;
-	private String mDisplayName;
 	private int mBytesPerFrame = 0;
 	private ISampleAdapter mSampleAdapter;
 	private AutomaticGainControl mAGC = new AutomaticGainControl();
 	
-	CopyOnWriteArrayList<Listener<RealBuffer>> mSampleListeners = 
+	CopyOnWriteArrayList<Listener<RealBuffer>> mSampleListeners = new CopyOnWriteArrayList<Listener<RealBuffer>>();
-					new CopyOnWriteArrayList<Listener<RealBuffer>>();
     
 	/**
 	 * Real Mixer Source - constructs a reader on the mixer/sound card target 
@@ -81,6 +79,25 @@ public class RealMixerSource extends RealSource
         mSampleAdapter = sampleAdapter;
     }
 
+	@Override
+	public void setFrequencyChangeListener(Listener<FrequencyChangeEvent> listener)
+	{
+		//Not implemented
+	}
+
+	@Override
+	public void removeFrequencyChangeListener()
+	{
+		//Not implemented
+	}
+
+	@Override
+	public Listener<FrequencyChangeEvent> getFrequencyChangeListener()
+	{
+		//Not implemented
+		return null;
+	}
+
 	@Override
 	public void reset()
 	{
@@ -133,23 +150,15 @@ public class RealMixerSource extends RealSource
 			 * buffer, otherwise send him a copy of the buffer */
 			if( it.hasNext() )
 			{
-//				next.receive( mAGC.process( samples.copyOf() ) );
 				next.receive( samples.copyOf() );
 			}
 			else
 			{
-//				next.receive( mAGC.process( samples ) );
 				next.receive( samples );
 			}
 		}
     }
     
-	@Override
-	public String toString()
-	{
-		return mDisplayName;
-	}
-	
     public int getSampleRate()
     {
 		if( mTargetDataLine != null )

src/source/tuner/TunerChannelSource.java

@@ -34,7 +34,9 @@ import source.ComplexSource;
 import source.SourceException;
 import source.tuner.frequency.FrequencyChangeEvent;
 import source.tuner.frequency.FrequencyChangeEvent.Event;
+import source.tuner.frequency.IFrequencyChangeListener;
 import source.tuner.frequency.IFrequencyChangeProcessor;
+import source.tuner.frequency.IFrequencyChangeProvider;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -65,6 +67,7 @@ public class TunerChannelSource extends ComplexSource implements IFrequencyChang
     private ComplexPrimeCICDecimate mDecimationFilter;
     private Listener<ComplexBuffer> mListener;
     private IFrequencyChangeProcessor mFrequencyChangeProcessor;
+    private DownstreamProcessor mDownstreamFrequencyEventProcessor = new DownstreamProcessor();
     private ScheduledFuture<?> mTaskHandle;
 
     private long mTunerFrequency = 0;
@@ -75,7 +78,6 @@ public class TunerChannelSource extends ComplexSource implements IFrequencyChang
 
     private AtomicBoolean mRunning = new AtomicBoolean();
     private boolean mExpended = false;
-    private int mCount;
 
     /**
      * Provides a Digital Drop Channel (DDC) to decimate the IQ output from a
@@ -109,7 +111,8 @@ public class TunerChannelSource extends ComplexSource implements IFrequencyChang
         mMixer = new Oscillator(frequencyOffset, mTuner.getTunerController().getSampleRate());
 
 		/* Fire a sample rate change event to setup the decimation chain */
-        frequencyChanged(new FrequencyChangeEvent(Event.NOTIFICATION_SAMPLE_RATE_CHANGE, mTuner.getTunerController().getSampleRate()));
+        frequencyChanged(new FrequencyChangeEvent(Event.NOTIFICATION_SAMPLE_RATE_CHANGE,
+            mTuner.getTunerController().getSampleRate()));
     }
 
     /**
@@ -131,6 +134,10 @@ public class TunerChannelSource extends ComplexSource implements IFrequencyChang
 
         if(mRunning.compareAndSet(false, true))
         {
+            //Broadcast current frequency and sample rate settings so all downstream components are aware
+            mDownstreamFrequencyEventProcessor.broadcastCurrentFrequency();
+            mDownstreamFrequencyEventProcessor.broadcastCurrentSampleRate();
+
             //Schedule the decimation task to run every 9 ms (111 iterations/second), an odd periodicity relative
             //to the inbound periodicity of 20 ms, to attempt to avoid thread queue contention
             mTaskHandle = executor.scheduleAtFixedRate(mDecimationProcessor, 0, 9, TimeUnit.MILLISECONDS);
@@ -184,6 +191,20 @@ public class TunerChannelSource extends ComplexSource implements IFrequencyChang
         }
     }
 
+    /**
+     * Changes the frequency correction value and broadcasts the change to the registered downstream listener.
+     * @param correction current frequency correction value.
+     */
+    private void setFrequencyCorrection(int correction)
+    {
+        mChannelFrequencyCorrection = correction;
+
+        updateMixerFrequencyOffset();
+
+        mDownstreamFrequencyEventProcessor.broadcast(
+            new FrequencyChangeEvent( Event.NOTIFICATION_CHANNEL_FREQUENCY_CORRECTION_CHANGE, mChannelFrequencyCorrection));
+    }
+
     public Tuner getTuner()
     {
         return mTuner;
@@ -242,21 +263,25 @@ public class TunerChannelSource extends ComplexSource implements IFrequencyChang
             case NOTIFICATION_FREQUENCY_CHANGE:
                 mTunerFrequency = event.getValue().longValue();
                 updateMixerFrequencyOffset();
-                break;
-            case REQUEST_CHANNEL_FREQUENCY_CORRECTION_CHANGE:
-                mChannelFrequencyCorrection = event.getValue().intValue();
 
-                updateMixerFrequencyOffset();
+                //Reset frequency correction so that downstream components can recalculate the value
-
+                setFrequencyCorrection(0);
-                if(mFrequencyChangeProcessor != null)
-                {
-                    mFrequencyChangeProcessor.frequencyChanged(new FrequencyChangeEvent(
-                        Event.NOTIFICATION_CHANNEL_FREQUENCY_CORRECTION_CHANGE, mChannelFrequencyCorrection));
-                }
                 break;
             case NOTIFICATION_SAMPLE_RATE_CHANGE:
                 int sampleRate = event.getValue().intValue();
+                setSampleRate(sampleRate);
+                break;
+            default:
+                break;
+        }
+    }
 
+    /**
+     * Updates the sample rate to the requested value and notifies any downstream components of the change
+     * @param sampleRate to set
+     */
+    private void setSampleRate(int sampleRate)
+    {
         if(mTunerSampleRate != sampleRate)
         {
             mMixer.setSampleRate(sampleRate);
@@ -269,10 +294,8 @@ public class TunerChannelSource extends ComplexSource implements IFrequencyChang
             mDecimationFilter.setListener(mListener);
 
             mTunerSampleRate = sampleRate;
-                }
+
-                break;
+            mDownstreamFrequencyEventProcessor.broadcastCurrentSampleRate();
-            default:
-                break;
         }
     }
 
@@ -282,10 +305,7 @@ public class TunerChannelSource extends ComplexSource implements IFrequencyChang
      */
     private void updateMixerFrequencyOffset()
     {
-        long offset = mTunerFrequency -
+        long offset = mTunerFrequency - mTunerChannel.getFrequency() - mChannelFrequencyCorrection;
-            mTunerChannel.getFrequency() -
-            mChannelFrequencyCorrection;
-
         mMixer.setFrequency(offset);
     }
 
@@ -299,6 +319,140 @@ public class TunerChannelSource extends ComplexSource implements IFrequencyChang
         return mTunerChannel.getFrequency();
     }
 
+    /**
+     * Implements IFrequencyChangeProvider to enable this source to broadcast frequency change events to downstream
+     * listeners.
+     *
+     * @param listener to receive downstream events
+     */
+    @Override
+    public void setFrequencyChangeListener(Listener<FrequencyChangeEvent> listener)
+    {
+        mDownstreamFrequencyEventProcessor.setFrequencyChangeListener(listener);
+    }
+
+    /**
+     * Implements IFrequencyChangeProvider to remove the frequency change listener from receiving down-stream frequency
+     * change events.
+      */
+    @Override
+    public void removeFrequencyChangeListener()
+    {
+        mDownstreamFrequencyEventProcessor.removeFrequencyChangeListener();
+    }
+
+    /**
+     * Implements IFrequencyChangeListener to receive frequency change events containing requests from downstream
+     * listeners to change frequency values.
+     * @return listener
+     */
+    @Override
+    public Listener<FrequencyChangeEvent> getFrequencyChangeListener()
+    {
+        return mDownstreamFrequencyEventProcessor.getFrequencyChangeListener();
+    }
+
+    /**
+     * Managers frequency change requests and notifications from/to any downstream component.  Downstream
+     * components are those that receive samples from this tuner channel source.  These downstream components will be
+     * notified of any frequency or sample rate change events and will also be able to request frequency correction
+     * updates.
+     */
+    public class DownstreamProcessor implements IFrequencyChangeListener, IFrequencyChangeProvider,
+        Listener<FrequencyChangeEvent>
+    {
+        //Listener to receive downstream events
+        private Listener<FrequencyChangeEvent> mListener;
+
+        /**
+         * Broadcasts the frequency change event to the downstream frequency change listener
+         * @param event to broadcast
+         */
+        public void broadcast(FrequencyChangeEvent event)
+        {
+            if(mListener != null)
+            {
+                mListener.receive(event);
+            }
+        }
+
+        /**
+         * Broadcasts the current frequency of this tuner channel source to the downstream listener
+         */
+        public void broadcastCurrentFrequency()
+        {
+            try
+            {
+                long frequency = getFrequency();
+                broadcast(new FrequencyChangeEvent(Event.NOTIFICATION_FREQUENCY_CHANGE, frequency));
+            }
+            catch(SourceException se)
+            {
+                mLog.error("Error obtaining frequency from tuner to broadcast downstream");
+            }
+        }
+
+        /**
+         * Broadcasts the current decimated sample rate of this tuner channel source
+         */
+        public void broadcastCurrentSampleRate()
+        {
+            try
+            {
+                //Note: downstream sample rate is currently a fixed value -- it will change in the future
+                broadcast(new FrequencyChangeEvent(Event.NOTIFICATION_SAMPLE_RATE_CHANGE, getSampleRate()));
+            }
+            catch(SourceException se)
+            {
+                mLog.error("Error obtaining sample rate from tuner to broadcast downstream");
+            }
+        }
+
+        /**
+         * Sets the downstream listener to receive frequency change events from this tuner channel source
+         * @param listener to receive events
+         */
+        @Override
+        public void setFrequencyChangeListener(Listener<FrequencyChangeEvent> listener)
+        {
+            mListener = listener;
+        }
+
+        /**
+         * Removes the downstream listener from receiving frequency change events.
+         */
+        @Override
+        public void removeFrequencyChangeListener()
+        {
+            mListener = null;
+        }
+
+        /**
+         * Listener for receiving frequency change events from downstream components
+         */
+        @Override
+        public Listener<FrequencyChangeEvent> getFrequencyChangeListener()
+        {
+            return this;
+        }
+
+        /**
+         * Processes frequency change events from downstream components.
+         * @param event to process
+         */
+        @Override
+        public void receive(FrequencyChangeEvent event)
+        {
+            switch(event.getEvent())
+            {
+                //Frequency correction requests are the only change requests supported from downstream components
+                case REQUEST_CHANNEL_FREQUENCY_CORRECTION_CHANGE:
+                    setFrequencyCorrection(event.getValue().intValue());
+                    break;
+            }
+        }
+    }
+
     /**
      * Decimates an inbound buffer of I/Q samples from the source down to the
      * standard 48000 channel sample rate

src/source/tuner/frequency/IFrequencyChangeProvider.java

@@ -1,9 +1,30 @@
+/*******************************************************************************
+ * 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 source.tuner.frequency;
 
 import sample.Listener;
 
+/**
+ * Provider of Frequency Change Events
+ */
 public interface IFrequencyChangeProvider
 {
-	public void setFrequencyChangeListener( Listener<FrequencyChangeEvent> listener );
+	void setFrequencyChangeListener( Listener<FrequencyChangeEvent> listener );
-	public void removeFrequencyChangeListener();
+	void removeFrequencyChangeListener();
 }

src/source/wave/ComplexWaveSource.java

@@ -1,6 +1,6 @@
 /*******************************************************************************
- *     SDR Trunk 
+ * sdrtrunk
- *     Copyright (C) 2014,2015 Dennis Sheirer
+ * 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
@@ -14,6 +14,7 @@
  *
  * 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 source.wave;
 
@@ -36,6 +37,7 @@ import sample.complex.ComplexBuffer;
 import source.ComplexSource;
 import source.IControllableFileSource;
 import source.IFrameLocationListener;
+import source.tuner.frequency.FrequencyChangeEvent;
 
 public class ComplexWaveSource extends ComplexSource implements IControllableFileSource
 {
@@ -55,6 +57,25 @@ public class ComplexWaveSource extends ComplexSource implements IControllableFil
     	mFile = file;
     }
 
+    @Override
+    public void setFrequencyChangeListener(Listener<FrequencyChangeEvent> listener)
+    {
+        //Not implemented
+    }
+
+    @Override
+    public void removeFrequencyChangeListener()
+    {
+        //Not implemented
+    }
+
+    @Override
+    public Listener<FrequencyChangeEvent> getFrequencyChangeListener()
+    {
+        //Not implemented
+        return null;
+    }
+
     @Override
 	public void reset()
 	{

src/source/wave/RealWaveSource.java

@@ -36,6 +36,7 @@ import sample.real.RealBuffer;
 import source.IControllableFileSource;
 import source.IFrameLocationListener;
 import source.RealSource;
+import source.tuner.frequency.FrequencyChangeEvent;
 
 public class RealWaveSource extends RealSource 
 	implements IControllableFileSource, AutoCloseable
@@ -56,6 +57,25 @@ public class RealWaveSource extends RealSource
     	mFile = file;
     }
 
+	@Override
+	public void setFrequencyChangeListener(Listener<FrequencyChangeEvent> listener)
+	{
+		//Not implemented
+	}
+
+	@Override
+	public void removeFrequencyChangeListener()
+	{
+		//Not implemented
+	}
+
+	@Override
+	public Listener<FrequencyChangeEvent> getFrequencyChangeListener()
+	{
+		//Not implemented
+		return null;
+	}
+
 
 	@Override
 	public void reset()

src/spectrum/OverlayPanel.java

@@ -50,6 +50,7 @@ public class OverlayPanel extends JPanel implements ChannelEventListener, IFrequ
     private static final long serialVersionUID = 1L;
 
     private final static Logger mLog = LoggerFactory.getLogger(OverlayPanel.class);
+    private final DecimalFormat PPM_FORMATTER = new DecimalFormat( "#.0" );
 
     private final static RenderingHints RENDERING_HINTS = new RenderingHints(RenderingHints.KEY_ANTIALIASING,
         RenderingHints.VALUE_ANTIALIAS_ON);
@@ -187,7 +188,6 @@ public class OverlayPanel extends JPanel implements ChannelEventListener, IFrequ
      * 6	64x Zoom
      *
      * @param zoom level, 0 - 6.
-     * @param offset into the FFT bins for start zoom window
      */
     public void setZoom(int zoom)
     {
@@ -412,20 +412,41 @@ public class OverlayPanel extends JPanel implements ChannelEventListener, IFrequ
     }
 
     /**
-     * Draws a vertical line at the xaxis
+     * Draws the Automatic Frequency Control (AFC) channel center offset
      */
-    private void drawAFC(Graphics2D graphics, double frequencyAxis, double errorAxis)
+    private void drawAFC(Graphics2D graphics, double frequencyAxis, double errorAxis, double bandwidth,
+                         int correction, long frequency)
     {
         double height = getSize().getHeight() - mSpectrumInset;
-        double lineHeight = height * 0.75d;
+        double verticalAxisTop = height * 0.88d;
+        double verticalAxisBottom = height * 0.98d;
+
+        double halfBandwidth = bandwidth / 2.0;
+        double errorEdgeStart = errorAxis - halfBandwidth;
+        double errorEdgeStop = errorAxis + halfBandwidth;
 
         graphics.setColor(Color.YELLOW);
 
-        //Vertical frequency error line
+        //Horizontal line connecting frequency and error line
-        graphics.draw(new Line2D.Double(errorAxis, lineHeight, errorAxis, height - 1.0d));
+        graphics.draw(new Line2D.Double(errorEdgeStart, verticalAxisBottom, errorEdgeStop, verticalAxisBottom));
 
-        //Horizontal line connecting frequency and error lines
+        //Vertical band edge lines
-        graphics.draw(new Line2D.Double(frequencyAxis, lineHeight, errorAxis, lineHeight));
+        graphics.draw(new Line2D.Double(errorEdgeStart, verticalAxisTop, errorEdgeStart, verticalAxisBottom));
+        graphics.draw(new Line2D.Double(errorEdgeStop, verticalAxisTop, errorEdgeStop, verticalAxisBottom));
+
+        double ppm = (double)correction / ((double)frequency / 1E6d);
+
+        String label = "PPM " + PPM_FORMATTER.format(ppm) ;
+
+        FontMetrics fontMetrics = graphics.getFontMetrics(this.getFont());
+
+        Rectangle2D rect = fontMetrics.getStringBounds(label, graphics);
+
+        //Only render the correction value label if the spacing is large enough
+        if(rect.getWidth() <= bandwidth && rect.getHeight() * 5 <= height)
+        {
+            graphics.drawString(label, (float)(errorEdgeStart + 1.0), (float)(verticalAxisBottom - 2.0));
+        }
     }
 
     /**
@@ -564,7 +585,8 @@ public class OverlayPanel extends JPanel implements ChannelEventListener, IFrequ
                     {
                         long error = frequency + correction;
 
-                        drawAFC(graphics, frequencyAxis, getAxisFromFrequency(error));
+                        drawAFC(graphics, frequencyAxis, getAxisFromFrequency(error), width, correction,
+                            tunerChannel.getFrequency());
                     }
                 }
             }

src/spectrum/SpectrumPanel.java

@@ -1,6 +1,6 @@
 /*******************************************************************************
- *     SDR Trunk 
+ * sdrtrunk
- *     Copyright (C) 2014,2015 Dennis Sheirer
+ * 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
@@ -14,56 +14,43 @@
  *
  * 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 spectrum;
 
-import java.awt.Color;
-import java.awt.Dimension;
-import java.awt.GradientPaint;
-import java.awt.Graphics;
-import java.awt.Graphics2D;
-import java.awt.Rectangle;
-import java.awt.RenderingHints;
-import java.awt.geom.GeneralPath;
-import java.awt.geom.Line2D;
-import java.util.Arrays;
-
-import javax.swing.JPanel;
-
-import org.apache.commons.lang3.Validate;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-import settings.ColorSetting;
-import settings.ColorSetting.ColorSettingName;
-import settings.Setting;
-import settings.SettingChangeListener;
-import settings.SettingsManager;
 import dsp.filter.smoothing.GaussianSmoothingFilter;
 import dsp.filter.smoothing.NoSmoothingFilter;
 import dsp.filter.smoothing.RectangularSmoothingFilter;
 import dsp.filter.smoothing.SmoothingFilter;
 import dsp.filter.smoothing.SmoothingFilter.SmoothingType;
 import dsp.filter.smoothing.TriangularSmoothingFilter;
+import org.apache.commons.lang3.Validate;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import settings.ColorSetting;
+import settings.ColorSetting.ColorSettingName;
+import settings.Setting;
+import settings.SettingChangeListener;
+import settings.SettingsManager;
 
-public class SpectrumPanel extends JPanel
+import javax.swing.*;
-							implements DFTResultsListener,
+import java.awt.*;
-									   SettingChangeListener,
+import java.awt.geom.GeneralPath;
-									   SpectralDisplayAdjuster
+import java.awt.geom.Line2D;
+import java.util.Arrays;
+
+public class SpectrumPanel extends JPanel implements DFTResultsListener, SettingChangeListener, SpectralDisplayAdjuster
 {
     private static final long serialVersionUID = 1L;
 
-	private final static Logger mLog = 
+    private final static Logger mLog = LoggerFactory.getLogger(SpectrumPanel.class);
-			LoggerFactory.getLogger( SpectrumPanel.class );
 
     private static final RenderingHints RENDERING_HINTS =
-    		new RenderingHints( RenderingHints.KEY_ANTIALIASING, 
+        new RenderingHints(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
-    							RenderingHints.VALUE_ANTIALIAS_ON );
 
     static
     {
-		RENDERING_HINTS.put( RenderingHints.KEY_RENDERING, 
+        RENDERING_HINTS.put(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
-							 RenderingHints.VALUE_RENDER_QUALITY );
     }
 
     private Color mColorSpectrumBackground;
@@ -87,7 +74,8 @@ public class SpectrumPanel extends JPanel
     private float mDBScale;
 
     private int mZoom = 0;
-	private int mZoomWindowOffset = 0;;
+    private int mZoomWindowOffset = 0;
+    ;
 
     private SettingsManager mSettingsManager;
 
@@ -278,12 +266,13 @@ public class SpectrumPanel extends JPanel
      * 3	8x Zoom
      * 4	16x Zoom
      * 5	32x Zoom
+     * 6    64x Zoom
      *
-     * @param zoom level, 0 - 5.
+     * @param zoom level, 0 - 6.
      */
     public void setZoom(int zoom)
     {
-    	Validate.isTrue( 0 <= zoom && zoom <= 5 );
+        Validate.isTrue(0 <= zoom && zoom <= 6, "Unrecognized Zoom Level: " + zoom);
 
         mZoom = zoom;
     }
@@ -427,7 +416,8 @@ public class SpectrumPanel extends JPanel
     }
 
     @Override
-    public void settingDeleted( Setting setting ) {  /* not implemented */ }
+    public void settingDeleted(Setting setting)
+    {  /* not implemented */ }
 
     /**
      * Returns the current inter-bin smoothing setting