Updates build to Version 0.2.0 Beta 8

the recent changes applied to RTL2832 Tuner controller for processing of
libusb transfer buffers.

README.md

@@ -1,18 +1,22 @@
-# sdrtrunk
+# sdrtrunk #
-A cross-platform java application for decoding, monitoring, recording and streaming trunked mobile and related radio protocols using Software Defined Radios (SDR).
+A cross-platform java application for decoding, monitoring and recording trunked 
+mobile and related radio protocols using Software Defined Radios (SDR).
 
+# Documentation #
 * [Getting Started](https://github.com/DSheirer/sdrtrunk/wiki/GettingStarted)
-* [User's Manual](https://github.com/DSheirer/sdrtrunk/wiki/UserManual)
+* [User's Manual (Version 0.2.0)](https://github.com/DSheirer/sdrtrunk/wiki/UserManual)
+* [Wiki](https://github.com/DSheirer/sdrtrunk/wiki)
+
+# Support Group and Error Reporting #
+You can get help with setting up the sdrtrunk application or report any errors
+that you encounter while running the application in the sdrtrunk Google Group at:
+ 
 * [Support](https://groups.google.com/forum/#!forum/sdrtrunk)
 
+# Updates #
+Subscribe to this group to receive updates about new releases and the ongoing 
+application development effort.
+
+* [Subscribe for Updates](https://groups.google.com/forum/#!forum/sdrtrunk)
+
 ![](https://github.com/DSheirer/sdrtrunk/wiki/images/SDRTrunk_application.png)
-<script>
-  (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
-  (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
-  m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
-  })(window,document,'script','//www.google-analytics.com/analytics.js','ga');
-
-  ga('create', 'UA-67489234-1', 'auto');
-  ga('send', 'pageview');
-
-</script>

build/build.xml

@@ -7,7 +7,7 @@
   <property name="major" value="0"/>
   <property name="minor" value="2"/>
   <property name="patch" value="0"/>
-  <property name="release" value="beta.4"/>
+  <property name="release" value="beta.8"/>
   <property name="filename" value="sdrtrunk_${major}.${minor}.${patch}-${release}"/>
 	
   <!-- Build properties -->

scripts/run_sdrtrunk_linux.sh

@@ -1,2 +1,2 @@
 #!/bin/bash
-java -XX:+UseG1GC -cp "*:libs/*" gui.SDRTrunk&
+java -XX:+UseG1GC -cp "*:libs/*" gui.SDRTrunk

src/alias/id/talkgroup/TalkgroupID.java

@@ -27,7 +27,6 @@ import audio.inverted.AudioType;
 public class TalkgroupID extends AliasID
 {
 	private String mTalkgroup;
-	private AudioType mAudioType;
 	
 	public TalkgroupID()
 	{
@@ -44,20 +43,9 @@ public class TalkgroupID extends AliasID
 		mTalkgroup = talkgroup;
 	}
 
-	@XmlAttribute
-	public AudioType getAudioType()
-	{
-		return mAudioType;
-	}
-	
-	public void setAudioType( AudioType type )
-	{
-		mAudioType = type;
-	}
-	
 	public boolean hasAudioType()
 	{
-		return mAudioType != null;
+		return false;
 	}
 	
 	public String toString()
@@ -66,13 +54,6 @@ public class TalkgroupID extends AliasID
 		
 		sb.append( "Talkgroup: " + mTalkgroup );
 		
-		if( mAudioType != null )
-		{
-			sb.append( " [Audio " );
-			sb.append( mAudioType.getShortDisplayString() );
-			sb.append( "]" );
-		}
-		
 		return sb.toString();
 	}
 

src/alias/id/talkgroup/TalkgroupIDEditor.java

@@ -1,6 +1,6 @@
 /*******************************************************************************
  *     SDR Trunk 
- *     Copyright (C) 2014 Dennis Sheirer
+ *     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
@@ -20,9 +20,7 @@ package alias.id.talkgroup;
 import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;
 
-import javax.swing.DefaultComboBoxModel;
 import javax.swing.JButton;
-import javax.swing.JComboBox;
 import javax.swing.JLabel;
 import javax.swing.JOptionPane;
 import javax.swing.JPanel;
@@ -30,7 +28,6 @@ import javax.swing.JTextArea;
 import javax.swing.JTextField;
 
 import net.miginfocom.swing.MigLayout;
-import audio.inverted.AudioType;
 import controller.ConfigurableNode;
 
 public class TalkgroupIDEditor extends JPanel implements ActionListener
@@ -38,19 +35,15 @@ public class TalkgroupIDEditor extends JPanel implements ActionListener
     private static final long serialVersionUID = 1L;
     private TalkgroupIDNode mTalkgroupIDNode;
     
-    private JLabel mLabelName;
     private JTextField mTextTalkgroupID;
-    private JLabel mLabelAudio;
-    private JComboBox<AudioType> mComboAudioTypes;
     
     private String mHelpText = "Enter a formatted talkgroup identifier.\n\n"
+    		+ "P25 Talkgroup Format: hexadecimal value, 4 characters for "
+    		+ "talkgroup or 6 characters for a mobile radio\n\n"
     		+ "LTR Talkgroup Format: A-HH-TTT (A=Area, H=Home Repeater, "
     		+ "T=Talkgroup)\n\n"
     		+ "Passport Talkgroup Format: xxxxx (up to 5-digit number)\n\n"
-            + "Wildcard: use one or more asterisks (*) for any talkgroup digits.\n\n"
+            + "Wildcard: use one or more asterisks (*) for any talkgroup digits.";
-            + "Audio: if the talkgroup uses simple frequency inversion, specify"
-            + " the inversion frequency from the dropdown list to automatically"
-            + " un-invert audio for this specific talkgroup";
 
 	public TalkgroupIDEditor( TalkgroupIDNode talkgroupIDNode )
 	{
@@ -72,22 +65,6 @@ public class TalkgroupIDEditor extends JPanel implements ActionListener
 
 		add( mTextTalkgroupID, "growx,push" );
 
-		add( new JLabel( "Audio:" ) );
-
-		mComboAudioTypes = new JComboBox<AudioType>();
-
-		mComboAudioTypes.setModel( 
-				new DefaultComboBoxModel<AudioType>( AudioType.values() ) );
-		
-		AudioType audioType = mTalkgroupIDNode.getTalkgroupID().getAudioType();
-		
-		if( audioType != null )
-		{
-			mComboAudioTypes.setSelectedItem( audioType );
-		}
-		
-		add( mComboAudioTypes, "growx,push" );
-		
 		JButton btnSave = new JButton( "Save" );
 		btnSave.addActionListener( TalkgroupIDEditor.this );
 		add( btnSave, "growx,push" );
@@ -117,14 +94,6 @@ public class TalkgroupIDEditor extends JPanel implements ActionListener
 				
 				((ConfigurableNode)mTalkgroupIDNode.getParent()).sort();
 
-				AudioType selected = mComboAudioTypes
-						.getItemAt( mComboAudioTypes.getSelectedIndex() );
-				
-				if( selected != null )
-				{
-					mTalkgroupIDNode.getTalkgroupID().setAudioType( selected );
-				}
-
 				mTalkgroupIDNode.save();
 				
 				mTalkgroupIDNode.show();
@@ -139,9 +108,6 @@ public class TalkgroupIDEditor extends JPanel implements ActionListener
 		{
 			mTextTalkgroupID.setText( 
 					mTalkgroupIDNode.getTalkgroupID().getTalkgroup() );
-
-			mComboAudioTypes.setSelectedItem( 
-					mTalkgroupIDNode.getTalkgroupID().getAudioType() );
 		}
 		
 		mTalkgroupIDNode.refresh();

src/audio/AudioManager.java

@@ -1,5 +1,3 @@
-package audio;
-
 /*******************************************************************************
  *     SDR Trunk 
  *     Copyright (C) 2014-2016 Dennis Sheirer
@@ -17,6 +15,8 @@ package audio;
  *     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 audio;
+
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Comparator;
@@ -50,7 +50,7 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
 {
 	private static final Logger mLog = LoggerFactory.getLogger( AudioManager.class );
 
-	public static final int AUDIO_TIMEOUT = 2000; //2 seconds
+	public static final int AUDIO_TIMEOUT = 1000; //1 second
 	
 	public static final String AUDIO_CHANNELS_PROPERTY = "audio.manager.channels";
 	public static final String AUDIO_MIXER_PROPERTY = "audio.manager.mixer";
@@ -182,7 +182,8 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
 		
 		for( AudioOutputConnection connection: mAudioOutputConnections )
 		{
-			if( connection.isConnected() && connection.isInactive() )
+			if( connection.isInactive() && 
+				mChannelConnectionMap.containsKey( connection.getSource() ) )
 			{
 				mChannelConnectionMap.remove( connection.getSource() );
 				connection.disconnect();
@@ -424,24 +425,21 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
 	}
 	
 	/**
-	 * Audio output connection manages a connection between a soure and an audio
+	 * Audio output connection manages a connection between a source and an audio
 	 * output and maintains current state information about the audio activity 
 	 * received form the source.
 	 */
-	public class AudioOutputConnection implements Listener<AudioEvent>
+	public class AudioOutputConnection
 	{
-		private static final long CALL_END_DELAY = 2000; //2 seconds
 		private static final int DISCONNECTED = -1;
 		
 		private AudioOutput mAudioOutput;
 		private int mPriority = 0;
-		private long mLastActivity = System.currentTimeMillis();
 		private int mSource = DISCONNECTED;
 		
 		public AudioOutputConnection( AudioOutput audioOutput )
 		{
 			mAudioOutput = audioOutput;
-			mAudioOutput.addAudioEventListener( this );
 		}
 		
 		public void receive( AudioPacket packet )
@@ -457,8 +455,6 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
 					updateLowestPriorityAssignment();
 				}
 				
-				updateTimestamp();
-				
 				if( mAudioOutput != null )
 				{
 					mAudioOutput.receive( packet );
@@ -481,11 +477,6 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
 			}
 		}
 		
-		private void updateTimestamp()
-		{
-			mLastActivity = System.currentTimeMillis();
-		}
-
 		/**
 		 * Terminates the audio output and prepares this connection for disposal
 		 */
@@ -518,7 +509,8 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
 		public void connect( int source )
 		{
 			mSource = source;
-			updateTimestamp();
+			
+			mAudioOutput.updateTimestamp();
 		}
 
 		/**
@@ -536,6 +528,7 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
 		public void disconnect()
 		{
 			mSource = DISCONNECTED;
+			mPriority = 0;
 		}
 
 		/**
@@ -544,28 +537,12 @@ public class AudioManager implements Listener<AudioPacket>, IAudioController
 		 */
 		public boolean isInactive()
 		{
-			return mLastActivity != Long.MAX_VALUE &&
+			return ( mAudioOutput.getLastActivityTimestamp() + AUDIO_TIMEOUT ) < System.currentTimeMillis();
-				   mLastActivity + CALL_END_DELAY < System.currentTimeMillis();
 		}
 		
 		public int getPriority()
 		{
 			return mPriority;
 		}
-		
-		@Override
-		public void receive( AudioEvent event )
-		{
-			switch( event.getType() )
-			{
-				case AUDIO_STARTED:
-				case AUDIO_STOPPED:
-				case AUDIO_CONTINUATION:
-					updateTimestamp();
-					break;
-				default:
-					break;
-			}
-		}
 	}
 }

src/audio/AudioPacket.java

@@ -64,6 +64,11 @@ public class AudioPacket
 		return mAudioData;
 	}
 	
+	public boolean hasAudioBuffer()
+	{
+		return mAudioData != null;
+	}
+	
 	public enum Type
 	{
 		AUDIO,

src/audio/metadata/AudioMetadata.java

@@ -1,19 +1,6 @@
-package audio.metadata;
-
-import java.util.ArrayList;
-import java.util.Iterator;
-import java.util.List;
-
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-import sample.Listener;
-import alias.Alias;
-import alias.priority.Priority;
-
 /*******************************************************************************
  *     SDR Trunk 
- *     Copyright (C) 2014,2015 Dennis Sheirer
+ *     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
@@ -28,15 +15,30 @@ import alias.priority.Priority;
  *     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 audio.metadata;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import sample.Listener;
+import alias.Alias;
+import alias.priority.Priority;
+
 public class AudioMetadata implements Listener<Metadata>
 {
 	protected static final Logger mLog = LoggerFactory.getLogger( AudioMetadata.class );
 
 	private int mSource;
-	private List<Metadata> mMetadata = new ArrayList<>();
+	private Map<MetadataType,Metadata> mMetadata = new HashMap<>();
 	private boolean mUpdated = false;
 
-	/* Channel Selectect == highest priority */
+	/* Channel Selected == highest priority */
 	private boolean mSelected = false;
 
 	/* Call Priority */
@@ -92,7 +94,8 @@ public class AudioMetadata implements Listener<Metadata>
 		copy.mPriority = mPriority;
 		copy.mSelected = mSelected;
 		copy.mRecordable = mRecordable;
-		copy.mMetadata.addAll( mMetadata );
+
+		copy.mMetadata.putAll( mMetadata );
 		copy.mUpdated = mUpdated;
 		copy.mIdentifier = new String( mIdentifier );
 		
@@ -106,25 +109,34 @@ public class AudioMetadata implements Listener<Metadata>
 	 */
 	public void reset()
 	{
-		Iterator<Metadata> it = mMetadata.iterator();
-		
-		while( it.hasNext() )
-		{
-			if( it.next().isTemporal() )
-			{
-				it.remove();
-			}
-		}
-
 		/* Reset recordable state, identifier and audio call priority levels
 		 * and reprocess the metadata */
 		mRecordable = mSourceRecordable;
 		setIdentifier( mSource );
 		mPriority = Priority.DEFAULT_PRIORITY;
 		
-		for( Metadata metadata: mMetadata )
+		List<MetadataType> toRemove = new ArrayList<>();
+
+		for( MetadataType type: mMetadata.keySet() )
 		{
-			processMetadata( metadata );
+			Metadata metadata = mMetadata.get( type );
+
+			if( metadata != null )
+			{
+				if( metadata.isTemporal() )
+				{
+					toRemove.add( type );
+				}
+				else
+				{
+					processMetadata( metadata );
+				}
+			}
+		}
+		
+		for( MetadataType type: toRemove )
+		{
+			mMetadata.remove( type );
 		}
 
 		mUpdated = true;
@@ -185,8 +197,14 @@ public class AudioMetadata implements Listener<Metadata>
 		}
 		else
 		{
-			mMetadata.add( metadata );
+			Metadata existing = mMetadata.get( metadata.getMetadataType() );
-			processMetadata( metadata );
+
+			if( existing == null || !existing.equals( metadata ) )
+			{
+				mMetadata.put( metadata.getMetadataType(), metadata );
+				processMetadata( metadata );
+				setUpdated( true );
+			}
 		}
 		
 		mUpdated = true;
@@ -195,26 +213,17 @@ public class AudioMetadata implements Listener<Metadata>
 	/**
 	 * Returns the complete set of metadata
 	 */
-	public List<Metadata> getMetadata()
+	public Map<MetadataType,Metadata> getMetadata()
 	{
 		return mMetadata;
 	}
 
 	/**
-	 * Returns the first metadata object matching the type, or null if the 
+	 * Returns the metadata object matching the type or null
-	 * metadata type is not found.
 	 */
 	public Metadata getMetadata( MetadataType type )
 	{
-		for( Metadata metadata: mMetadata )
+		return mMetadata.get( type );
-		{
-			if( metadata.getMetadataType() == type )
-			{
-				return metadata;
-			}
-		}
-		
-		return null;
 	}
 
 	/**
@@ -296,11 +305,11 @@ public class AudioMetadata implements Listener<Metadata>
 		sb.append( getPriority() );
 		sb.append( " updated:" + isUpdated() );
 		sb.append( " " );
-		for( Metadata m: getMetadata() )
+		for( Entry<MetadataType,Metadata> entry: getMetadata().entrySet() )
 		{
-			sb.append( m.getKey() );
+			sb.append( entry.getValue().getKey() );
 			sb.append( ":" );
-			sb.append( m.getValue() );
+			sb.append( entry.getValue().getValue() );
 			sb.append( " " );
 		}
 

src/audio/metadata/Metadata.java

@@ -103,4 +103,44 @@ public class Metadata
 		
 		return sb.toString();
 	}
+	
+	public boolean equals( Metadata other )
+	{
+		if( mMetadataType != other.getMetadataType() )
+		{
+			return false;
+		}
+
+		if( mTemporal != other.isTemporal() )
+		{
+			return false;
+		}
+		
+		if( mValue != null && other.getValue() != null && 
+			!mValue.contentEquals( other.getValue() ))
+		{
+			return false;
+		}
+		
+		if( ( mValue == null && other.getValue() != null ) ||
+			( mValue != null && other.getValue() == null ) )
+		{
+			return false;
+		}
+		
+		if( mValueAlias != null && other.getAlias() != null && 
+			!mValueAlias.getName().contentEquals( other.getAlias().getName() ))
+		{
+			return false;
+		}
+		
+		if( ( mValueAlias == null && other.getAlias() != null ) ||
+			( mValueAlias != null && other.getAlias() == null ) )
+		{
+			return false;
+		}
+
+		return true;
+	}
+
 }

src/audio/output/AudioOutput.java

@@ -1,37 +1,148 @@
 package audio.output;
 
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.concurrent.LinkedTransferQueue;
+import java.util.concurrent.ScheduledFuture;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 
+import javax.sound.sampled.AudioFormat;
+import javax.sound.sampled.BooleanControl;
+import javax.sound.sampled.Control;
 import javax.sound.sampled.FloatControl;
+import javax.sound.sampled.Line;
+import javax.sound.sampled.LineEvent;
+import javax.sound.sampled.LineListener;
+import javax.sound.sampled.LineUnavailableException;
+import javax.sound.sampled.Mixer;
+import javax.sound.sampled.SourceDataLine;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import sample.Broadcaster;
 import sample.Listener;
+import source.mixer.MixerChannel;
 import audio.AudioEvent;
-import audio.AudioEvent.Type;
 import audio.AudioPacket;
+import audio.AudioPacket.Type;
 import audio.metadata.AudioMetadata;
 import controller.ThreadPoolManager;
+import controller.ThreadPoolManager.ThreadType;
 
-public abstract class AudioOutput implements Listener<AudioPacket>
+public abstract class AudioOutput implements Listener<AudioPacket>, LineListener
 {
 	private final static Logger mLog = LoggerFactory.getLogger( AudioOutput.class );
 	
-	private AtomicBoolean mSquelched = new AtomicBoolean( false );
+	private LinkedTransferQueue<AudioPacket> mBuffer = new LinkedTransferQueue<>();
+	private int mBufferStartThreshold;
+	private int mBufferStopThreshold;
+
 	private Listener<AudioMetadata> mAudioMetadataListener;
+	private Broadcaster<AudioEvent> mAudioEventBroadcaster = new Broadcaster<>();
 
-	protected Broadcaster<AudioEvent> mAudioEventBroadcaster = new Broadcaster<>();
+	private ThreadPoolManager mThreadPoolManager;
-	protected LinkedTransferQueue<AudioPacket> mBuffer = new LinkedTransferQueue<>();
+	private ScheduledFuture<?> mProcessorTask;
-	protected ThreadPoolManager mThreadPoolManager;
-	protected boolean mCanProcessAudio;
-	protected long mLastActivity;
 
-	public AudioOutput( ThreadPoolManager threadPoolManager )
+	private SourceDataLine mOutput;
+	private Mixer mMixer;
+	private MixerChannel mMixerChannel;
+	private FloatControl mGainControl;
+	private BooleanControl mMuteControl;
+
+	private AudioEvent mAudioStartEvent;
+	private AudioEvent mAudioStopEvent;
+
+	private boolean mCanProcessAudio = false;
+	private long mLastActivity = System.currentTimeMillis();
+
+	/**
+	 * Single audio channel playback with automatic starting and stopping of the
+	 * underlying sourcedataline specified by the mixer and mixer channel
+	 * arguments.
+	 * 
+	 * Maintains an internal non-blocking audio packet queue and processes this
+	 * queue 25 times a second (every 40 ms).
+	 * 
+	 * @param threadPoolManager for assigning buffer processing schedule task
+	 * @param mixer to obtain source data line
+	 * @param mixerChannel either mono or left/right stereo
+	 * @param audioFormat to use during playback
+	 * @param lineInfo to use when obtaining the source data line
+	 * @param requestedBufferSize of approximately 1 second of audio
+	 */
+	public AudioOutput( ThreadPoolManager threadPoolManager,
+						Mixer mixer,
+						MixerChannel mixerChannel,
+						AudioFormat audioFormat,
+						Line.Info lineInfo,
+						int requestedBufferSize )
 	{
 		mThreadPoolManager = threadPoolManager;
+		mMixer = mixer;
+		mMixerChannel = mixerChannel;
+		
+		try
+		{
+			mOutput = (SourceDataLine)mMixer.getLine( lineInfo ); 
+			
+			if( mOutput != null )
+			{
+				mOutput.open( audioFormat, requestedBufferSize );
+				
+				//Start threshold: buffer is full with 10% or less of capacity remaining
+				mBufferStartThreshold = (int)( mOutput.getBufferSize() * 0.10 );
+
+				//Stop threshold: buffer is empty with 90% or more capacity available
+				mBufferStopThreshold = (int)( mOutput.getBufferSize() * 0.90 );
+
+				mOutput.addLineListener( this );
+				
+				if( mOutput != null )
+				{
+					try
+					{
+						Control gain = mOutput.getControl( FloatControl.Type.MASTER_GAIN );
+						mGainControl = (FloatControl)gain;
+					}
+					catch( IllegalArgumentException iae )
+					{
+						mLog.warn( "Couldn't obtain MASTER GAIN control for stereo line [" + 
+							mixer.getMixerInfo().getName() + " | " + getChannelName() + "]" );
+					}
+					
+					try
+					{
+						Control mute = mOutput.getControl( BooleanControl.Type.MUTE );
+						mMuteControl = (BooleanControl)mute;
+					}
+					catch( IllegalArgumentException iae )
+					{
+						mLog.warn( "Couldn't obtain MUTE control for stereo line [" + 
+							mixer.getMixerInfo().getName() + " | " + getChannelName() + "]" );
+					}
+					
+					/* Run the queue processor task every 40 milliseconds or 25 times a second */
+					mProcessorTask = mThreadPoolManager.scheduleFixedRate( 
+						ThreadType.AUDIO_PROCESSING, new BufferProcessor(), 
+						40, TimeUnit.MILLISECONDS );
+				}
+				
+				mAudioStartEvent = new AudioEvent( AudioEvent.Type.AUDIO_STARTED, 
+						getChannelName() );
+				mAudioStopEvent = new AudioEvent( AudioEvent.Type.AUDIO_STOPPED, 
+						getChannelName() );
+
+				mCanProcessAudio = true;
+			}
+		} 
+        catch ( LineUnavailableException e )
+		{
+        	mLog.error( "Couldn't obtain audio source data line for "
+    			+ "audio output - mixer [" + mMixer.getMixerInfo().getName() + "]" );
+		}
 	}
 	
 	public void reset()
@@ -44,47 +155,50 @@ public abstract class AudioOutput implements Listener<AudioPacket>
 	{
 		mCanProcessAudio = false;
 
+		if( mProcessorTask != null && mThreadPoolManager != null )
+		{
+			mThreadPoolManager.cancel( mProcessorTask );
+		}
+		
+		mThreadPoolManager = null;
+		mProcessorTask = null;
+
 		mBuffer.clear();
 
 		mAudioEventBroadcaster.dispose();
 		mAudioEventBroadcaster = null;
 		mAudioMetadataListener = null;
 		
-		mThreadPoolManager = null;
+		if( mOutput != null )
-	}
-	
-	public abstract String getChannelName();
-	
-	public abstract void setMuted( boolean muted );
-	public abstract boolean isMuted();
-	
-	public abstract FloatControl getGainControl();
-	public abstract boolean hasGainControl();
-	
-	protected void broadcast( AudioMetadata metadata )
-	{
-		if( mAudioMetadataListener != null )
 		{
-			mAudioMetadataListener.receive( metadata );
+			mOutput.close();
 		}
+		
+		mOutput = null;
+		mGainControl = null;
+		mMuteControl = null;
 	}
 
-	protected void broadcast( AudioEvent audioEvent )
+	/**
+	 * Converts the audio packet data into a byte buffer format appropriate for
+	 * the underlying source data line.
+	 */
+	protected abstract ByteBuffer convert( AudioPacket packet );
+
+	/**
+	 * Audio output channel name 
+	 */
+	public String getChannelName()
 	{
-		mAudioEventBroadcaster.broadcast( audioEvent );
+		return mMixerChannel.getLabel();
 	}
 	
-	public void setSquelched( boolean squelched )
+	/**
+	 * Mixer Channel for this audio output
+	 */
+	protected MixerChannel getMixerChannel()
 	{
-		mSquelched.set( squelched );
+		return mMixerChannel;
-		
-		broadcast( new AudioEvent( squelched ? Type.AUDIO_SQUELCHED : 
-			Type.AUDIO_UNSQUELCHED, getChannelName() ) );
-	}
-	
-	public boolean isSquelched()
-	{
-		return mSquelched.get();
 	}
 
 	/**
@@ -100,6 +214,14 @@ public abstract class AudioOutput implements Listener<AudioPacket>
 		mAudioEventBroadcaster.removeListener( listener );
 	}
 	
+	/**
+	 * Broadcasts an audio event to the registered listener
+	 */
+	private void broadcast( AudioEvent audioEvent )
+	{
+		mAudioEventBroadcaster.broadcast( audioEvent );
+	}
+	
 	/**
 	 * Registers a single listener to receive the audio metadata from each 
 	 * audio packet
@@ -115,21 +237,200 @@ public abstract class AudioOutput implements Listener<AudioPacket>
 	}
 
 	/**
-	 * Timestamp when most recent buffer was received
+	 * Broadcasts audio metadata to the registered listener
 	 */
-	public long getLastBufferReceived()
+	private void broadcast( AudioMetadata metadata )
+	{
+		if( mAudioMetadataListener != null )
+		{
+			mAudioMetadataListener.receive( metadata );
+		}
+	}
+
+	/**
+	 * Timestamp of either last buffer received or last buffer processed
+	 */
+	public long getLastActivityTimestamp()
 	{
 		return mLastActivity;
 	}
 
+	/**
+	 * Updates the last activity timestamp to current system time
+	 */
+	public void updateTimestamp()
+	{
+		mLastActivity = System.currentTimeMillis();
+	}
+	
 	@Override
 	public void receive( AudioPacket packet )
 	{
 		if( mCanProcessAudio )
 		{
-			mLastActivity = System.currentTimeMillis();
+			//Update the activity timestamp so that this audio output doesn't
+			//get disconnected before it starts processing the audio stream
+			updateTimestamp();
 			
 			mBuffer.add( packet );
 		}
 	}
+	
+	public class BufferProcessor implements Runnable
+	{
+		private AtomicBoolean mProcessing = new AtomicBoolean();
+		
+		public BufferProcessor()
+		{
+		}
+
+		@Override
+		public void run()
+		{
+			try
+			{
+				/* The processing flag ensures that only one instance of the
+				 * processor can run at any given time */
+				if( mProcessing.compareAndSet( false, true ) )
+				{
+					List<AudioPacket> packets = new ArrayList<AudioPacket>();
+					
+					mBuffer.drainTo( packets );
+					
+					for( AudioPacket packet: packets )
+					{
+						if( packet.getType() == Type.AUDIO )
+						{
+							broadcast( packet.getAudioMetadata() );
+
+							ByteBuffer buffer = convert( packet );
+							
+							int wrote = 0;
+							
+							if( !mOutput.isRunning() )
+							{
+								int toWrite = mOutput.available();
+								
+								if( toWrite > buffer.array().length )
+								{
+									toWrite = buffer.array().length;
+								}
+								
+								//Top off the buffer and check if we can start it
+								wrote += mOutput.write( buffer.array(), 0, toWrite );
+								
+								checkStart();
+							}
+
+							if( mOutput.isRunning() && wrote < buffer.array().length )
+							{
+								//Blocking write 
+								wrote += mOutput.write( buffer.array(), wrote, 
+									buffer.array().length - wrote );
+							}
+							
+							updateTimestamp();
+						}
+					}
+
+					checkStop();
+					
+					mProcessing.set( false );
+				}
+			}
+			catch( Exception e )
+			{
+				mLog.error( "Error while processing audio buffers", e );
+			}
+		}
+		
+		/**
+		 * Starts audio playback once audio buffer is almost full and remaining 
+		 * capacity falls below the start threshold.
+		 */
+		private void checkStart()
+		{
+			if( mCanProcessAudio && 
+				!mOutput.isRunning() && 
+				mOutput.available() <= mBufferStartThreshold )
+			{
+				mOutput.start();
+			}
+		}
+
+		/**
+		 * Stops audio playback and drains the audio buffer to empty when the
+		 * audio buffer is mostly empty and the available buffer capacity 
+		 * exceeds the stop threshold
+		 */
+		private void checkStop()
+		{
+			if( mCanProcessAudio && 
+				mOutput.isRunning() &&
+				mOutput.available() >= mBufferStopThreshold )
+			{
+				mOutput.drain();
+				mOutput.stop();
+			}
+		}
+	}
+	
+	/**
+	 * Sets the mute state for this audio output channel
+	 */
+	public void setMuted( boolean muted )
+	{
+		if( mMuteControl != null )
+		{
+			mMuteControl.setValue( muted );
+			
+			broadcast( new AudioEvent( muted ? AudioEvent.Type.AUDIO_MUTED : 
+				AudioEvent.Type.AUDIO_UNMUTED, getChannelName() ) );
+		}
+	}
+
+	/**
+	 * Current mute state for this audio output channel
+	 */
+	public boolean isMuted()
+	{
+		if( mMuteControl != null )
+		{
+			return mMuteControl.getValue();
+		}
+		
+		return false;
+	}
+
+	/**
+	 * Gain/volume control for this audio output channel, if one is available.
+	 */
+	public FloatControl getGainControl()
+	{
+		return mGainControl;
+	}
+
+	public boolean hasGainControl()
+	{
+		return mGainControl != null;
+	}
+	
+	/**
+	 * Monitors the source data line playback state and broadcasts audio events
+	 * to the registered listener as the state changes
+	 */
+	@Override
+	public void update( LineEvent event )
+	{
+		LineEvent.Type type = event.getType();
+
+		if( type == LineEvent.Type.START )
+		{
+			mAudioEventBroadcaster.broadcast( mAudioStartEvent );
+		}
+		else if( type == LineEvent.Type.STOP )
+		{
+			mAudioEventBroadcaster.broadcast( mAudioStopEvent );
+		}
+	}
 }

src/audio/output/MonoAudioOutput.java

@@ -3,273 +3,55 @@ package audio.output;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.nio.ShortBuffer;
-import java.util.ArrayList;
-import java.util.List;
-import java.util.concurrent.ScheduledFuture;
-import java.util.concurrent.TimeUnit;
-import java.util.concurrent.atomic.AtomicBoolean;
 
-import javax.sound.sampled.BooleanControl;
-import javax.sound.sampled.Control;
-import javax.sound.sampled.FloatControl;
-import javax.sound.sampled.LineUnavailableException;
 import javax.sound.sampled.Mixer;
-import javax.sound.sampled.SourceDataLine;
-
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 import source.mixer.MixerChannel;
-import audio.AudioEvent;
 import audio.AudioFormats;
 import audio.AudioPacket;
-import audio.AudioPacket.Type;
 import controller.ThreadPoolManager;
-import controller.ThreadPoolManager.ThreadType;
 
 /**
- * Mono Audio output with automatic flow control based on the availability of 
+ * Mono Audio output implementation
- * audio data packets.  
  */
 public class MonoAudioOutput extends AudioOutput
 {
-	private final static Logger mLog = LoggerFactory.getLogger( MonoAudioOutput.class );
-
-	/* Output line buffer size is set at one half second of audio at 48 kHz and
-	 * two bytes per sample */
 	private final static int BUFFER_SIZE = 48000;
 	
-	/* The queue processor will run every 20 milliseconds checking for inbound
-	 * audio and automatically starting or stopping audio playback.  We set the 
-	 * data line available space threshold to start when we're 20 ms away from 
-	 * being full, and the stop threshold when 20 ms away from being empty */
-	private final static int SAMPLE_SIZE_40_MS = BUFFER_SIZE / 25;
-	private final static int START_THRESHOLD = SAMPLE_SIZE_40_MS;
-	private final static int STOP_THRESHOLD = BUFFER_SIZE - SAMPLE_SIZE_40_MS;
-
-	private SourceDataLine mOutput;
-	private FloatControl mGainControl;
-	private BooleanControl mMuteControl;
-	
-	private AudioEvent mAudioStartEvent;
-	private AudioEvent mAudioStopEvent;
-	private AudioEvent mAudioContinuationEvent;
-	
-	private ScheduledFuture<?> mProcessorTask;
-	
 	public MonoAudioOutput( ThreadPoolManager threadPoolManager, Mixer mixer )
 	{
-		super( threadPoolManager );
+		super( threadPoolManager, 
-
+			   mixer, 
-		mAudioStartEvent = new AudioEvent( AudioEvent.Type.AUDIO_STARTED, 
+			   MixerChannel.MONO, 
-				getChannelName() );
+			   AudioFormats.PCM_SIGNED_48KHZ_16BITS_MONO, 
-		mAudioStopEvent = new AudioEvent( AudioEvent.Type.AUDIO_STOPPED, 
+			   AudioFormats.MONO_SOURCE_DATALINE_INFO, 
-				getChannelName() );
+			   BUFFER_SIZE  );
-		mAudioContinuationEvent = new AudioEvent( AudioEvent.Type.AUDIO_CONTINUATION, 
-				getChannelName() );
-
-		try
-		{
-			mOutput = (SourceDataLine)mixer.getLine( 
-					AudioFormats.MONO_SOURCE_DATALINE_INFO );
-			
-			if( mOutput != null )
-			{
-				mOutput.open( AudioFormats.PCM_SIGNED_48KHZ_16BITS_MONO, BUFFER_SIZE );
-				mCanProcessAudio = true;
-			}
-		} 
-        catch ( LineUnavailableException e )
-		{
-        	mLog.error( "Couldn't obtain source data line for 48kHz PCM mono "
-        			+ "audio output" );
-		}
-		
-		if( mOutput != null )
-		{
-			try
-			{
-				Control gain = mOutput.getControl( FloatControl.Type.MASTER_GAIN );
-				mGainControl = (FloatControl)gain;
-			}
-			catch( IllegalArgumentException iae )
-			{
-				mLog.warn( "Couldn't obtain MASTER GAIN control for mono line [" + 
-					mixer.getMixerInfo().getName() + "]" );
-			}
-			
-			try
-			{
-				Control mute = mOutput.getControl( BooleanControl.Type.MUTE );
-				mMuteControl = (BooleanControl)mute;
-			}
-			catch( IllegalArgumentException iae )
-			{
-				mLog.warn( "Couldn't obtain MUTE control for mono line [" + 
-					mixer.getMixerInfo().getName() + "]" );
-			}
-			
-			/* Run the queue processor task every 40 milliseconds */
-			mProcessorTask = mThreadPoolManager.scheduleFixedRate( 
-				ThreadType.AUDIO_PROCESSING, new QueueProcessor(), 
-				40, TimeUnit.MILLISECONDS );
-		}
 	}
 
-	@Override
+	/**
-	public String getChannelName()
+	 * Converts the audio packet data into mono audio frames.
+	 */
+	protected ByteBuffer convert( AudioPacket packet )
 	{
-		return MixerChannel.MONO.getLabel();
+		if( packet.hasAudioBuffer() )
-	}
-
-	public void dispose()
-	{
-		if( mProcessorTask != null && mThreadPoolManager != null )
 		{
-			mThreadPoolManager.cancel( mProcessorTask );
+			float[] samples = packet.getAudioBuffer().getSamples();
-		}
 			
-		mProcessorTask = null;
+			/* Little-endian byte buffer */
+			ByteBuffer buffer = 
+				ByteBuffer.allocate( samples.length * 2 )
+						.order( ByteOrder.LITTLE_ENDIAN );
 
-		super.dispose();
+			ShortBuffer shortBuffer = buffer.asShortBuffer();
 
-		if( mOutput != null )
+			for( float sample: samples )
-		{
-			mOutput.close();
-		}
-		
-		mOutput = null;
-		mGainControl = null;
-		mMuteControl = null;
-	}
-	
-	public class QueueProcessor implements Runnable
-	{
-		private AtomicBoolean mProcessing = new AtomicBoolean();
-		
-		@Override
-		public void run()
-		{
-			try
 			{
-				/* The mProcessing flag ensures that only one instance of the
+				shortBuffer.put( (short)( sample * Short.MAX_VALUE ) );
-				 * processor can run at any given time */
-				if( mProcessing.compareAndSet( false, true ) )
-				{
-					List<AudioPacket> packets = new ArrayList<AudioPacket>();
-					
-					mBuffer.drainTo( packets );
-					
-					if( packets.size() > 0 )
-					{
-						broadcast( mAudioContinuationEvent );
-						
-						for( AudioPacket packet: packets )
-						{
-							if( mCanProcessAudio )
-							{
-								if( isSquelched() )
-								{
-									checkStop();
-								}
-								else if( packet.getType() == Type.AUDIO )
-								{
-									float[] samples = packet.getAudioBuffer().getSamples();
-									
-									/* Little-endian byte buffer */
-									ByteBuffer buffer = 
-										ByteBuffer.allocate( samples.length * 2 )
-												.order( ByteOrder.LITTLE_ENDIAN );
-									
-									ShortBuffer shortBuffer = buffer.asShortBuffer();
-
-									for( float sample: samples )
-									{
-										shortBuffer.put( (short)( sample * Short.MAX_VALUE ) );
-									}
-									
-									//This is a blocking write
-									mOutput.write( buffer.array(), 0, buffer.array().length );
-
-									checkStart();
-
-									broadcast( packet.getAudioMetadata() );
-
-									mLastActivity = System.currentTimeMillis();
-								}
-							}
-						}
-					}
-					else
-					{
-						checkStop();
-					}
-					
-					mProcessing.set( false );
-				}
-			}
-			catch( Exception e )
-			{
-				mLog.error( "Error while processing audio buffers", e );
 			}
+			
+			return buffer;
 		}
 		
-		private void checkStart()
+		return null;
-		{
-			if( mCanProcessAudio && !isSquelched() && 
-				!mOutput.isRunning() && mOutput.available() <= START_THRESHOLD )
-			{
-				mOutput.start();
-				
-				mAudioEventBroadcaster.broadcast( mAudioStartEvent );
-			}
-		}
-		
-		private void checkStop()
-		{
-			if( mCanProcessAudio && mOutput.isRunning() &&
-				( mOutput.available() >= STOP_THRESHOLD || isSquelched() ) )
-			{
-				mOutput.drain();
-				mOutput.stop();
-
-				mAudioEventBroadcaster.broadcast( mAudioStopEvent );
-			}
-		}
-	}
-
-	@Override
-	public void setMuted( boolean muted )
-	{
-		if( mMuteControl != null )
-		{
-			mMuteControl.setValue( muted );
-			
-			broadcast( new AudioEvent( muted ? AudioEvent.Type.AUDIO_MUTED : 
-				AudioEvent.Type.AUDIO_UNMUTED, getChannelName() ) );
-		}
-	}
-
-	@Override
-	public boolean isMuted()
-	{
-		if( mMuteControl != null )
-		{
-			return mMuteControl.getValue();
-		}
-		
-		return false;
-	}
-
-	@Override
-	public FloatControl getGainControl()
-	{
-		return mGainControl;
-	}
-
-	@Override
-	public boolean hasGainControl()
-	{
-		return mGainControl != null;
 	}
 }

src/audio/output/StereoAudioOutput.java

@@ -3,302 +3,69 @@ package audio.output;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.nio.ShortBuffer;
-import java.util.ArrayList;
-import java.util.List;
-import java.util.concurrent.ScheduledFuture;
-import java.util.concurrent.TimeUnit;
-import java.util.concurrent.atomic.AtomicBoolean;
 
-import javax.sound.sampled.BooleanControl;
-import javax.sound.sampled.Control;
-import javax.sound.sampled.FloatControl;
-import javax.sound.sampled.LineUnavailableException;
 import javax.sound.sampled.Mixer;
-import javax.sound.sampled.SourceDataLine;
-
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
 
 import source.mixer.MixerChannel;
-import audio.AudioEvent;
 import audio.AudioFormats;
 import audio.AudioPacket;
-import audio.AudioPacket.Type;
 import controller.ThreadPoolManager;
-import controller.ThreadPoolManager.ThreadType;
 
 /**
- * Mono Audio output in stereo format with automatic flow control based on the 
+ * Stereo audio output implementation.  
- * availability of audio data packets.  
  */
 public class StereoAudioOutput extends AudioOutput
 {
-	private final static Logger mLog = LoggerFactory.getLogger( StereoAudioOutput.class );
-
-	/* Output line buffer size is set at one half second of audio at 48 kHz and
-	 * two bytes per sample for two channels */
 	private final static int BUFFER_SIZE = 96000;
 	
-	/* The queue processor will run every 20 milliseconds checking for inbound
-	 * audio and automatically starting or stopping audio playback.  We set the 
-	 * data line available space threshold to start when we're 20 ms away from 
-	 * being full, and the stop threshold when 20 ms away from being empty */
-	private final static int SAMPLE_SIZE_40_MS = BUFFER_SIZE / 25;
-	private final static int START_THRESHOLD = SAMPLE_SIZE_40_MS;
-	private final static int STOP_THRESHOLD = BUFFER_SIZE - SAMPLE_SIZE_40_MS;
-
-	private SourceDataLine mOutput;
-	private FloatControl mGainControl;
-	private BooleanControl mMuteControl;
-	
-	private AudioEvent mAudioStartEvent;
-	private AudioEvent mAudioStopEvent;
-	private AudioEvent mAudioContinuationEvent;
-	
-	private MixerChannel mMixerChannel;
-	
-	private ScheduledFuture<?> mProcessorTask;
-	
 	public StereoAudioOutput( ThreadPoolManager threadPoolManager, 
 			Mixer mixer, MixerChannel channel )
 	{
-		super( threadPoolManager );
+		super( threadPoolManager, 
-		
+			   mixer, 
-		assert( channel == MixerChannel.LEFT || channel == MixerChannel.RIGHT );
+			   channel, 
-		
+			   AudioFormats.PCM_SIGNED_48KHZ_16BITS_STEREO, 
-		mMixerChannel = channel;
+			   AudioFormats.STEREO_SOURCE_DATALINE_INFO, 
-
+			   BUFFER_SIZE  );
-		mAudioStartEvent = new AudioEvent( AudioEvent.Type.AUDIO_STARTED, 
-				getChannelName() );
-		mAudioStopEvent = new AudioEvent( AudioEvent.Type.AUDIO_STOPPED, 
-				getChannelName() );
-		mAudioContinuationEvent = new AudioEvent( AudioEvent.Type.AUDIO_CONTINUATION, 
-				getChannelName() );
-
-		try
-		{
-			mOutput = (SourceDataLine)mixer.getLine( 
-					AudioFormats.STEREO_SOURCE_DATALINE_INFO );
-			
-			if( mOutput != null )
-			{
-				mOutput.open( AudioFormats.PCM_SIGNED_48KHZ_16BITS_STEREO, BUFFER_SIZE );
-				mCanProcessAudio = true;
-			}
-		} 
-        catch ( LineUnavailableException e )
-		{
-        	mLog.error( "Couldn't obtain source data line for 48kHz PCM stereo "
-        			+ "audio output - mixer [" + mixer.getMixerInfo().getName() + 
-        			"] channel [" + mMixerChannel.name() + "]" );
-		}
-		
-		if( mOutput != null )
-		{
-			try
-			{
-				Control gain = mOutput.getControl( FloatControl.Type.MASTER_GAIN );
-				mGainControl = (FloatControl)gain;
-			}
-			catch( IllegalArgumentException iae )
-			{
-				mLog.warn( "Couldn't obtain MASTER GAIN control for stereo line [" + 
-					mixer.getMixerInfo().getName() + " | " + channel.name() + "]" );
-			}
-			
-			try
-			{
-				Control mute = mOutput.getControl( BooleanControl.Type.MUTE );
-				mMuteControl = (BooleanControl)mute;
-			}
-			catch( IllegalArgumentException iae )
-			{
-				mLog.warn( "Couldn't obtain MUTE control for stereo line [" + 
-					mixer.getMixerInfo().getName() + " | " + channel.name() + "]" );
-			}
-			
-			/* Run the queue processor task every 40 milliseconds */
-			mProcessorTask = mThreadPoolManager.scheduleFixedRate( 
-				ThreadType.AUDIO_PROCESSING, new QueueProcessor(), 
-				40, TimeUnit.MILLISECONDS );
-		}
 	}
 
-	@Override
+	/**
-	public String getChannelName()
+	 * Converts the audio packet data into stereo audio frames with the mixer
+	 * channel containing the audio and the other channel containing zero 
+	 * valued (silent) samples.
+	 */
+	protected ByteBuffer convert( AudioPacket packet )
 	{
-		return mMixerChannel.getLabel();
+		if( packet.hasAudioBuffer() )
-	}
-
-	public void dispose()
-	{
-		if( mProcessorTask != null && mThreadPoolManager != null )
 		{
-			mThreadPoolManager.cancel( mProcessorTask );
+			float[] samples = packet.getAudioBuffer().getSamples();
-		}
 			
-		mProcessorTask = null;
+			/* Little-endian byte buffer */
+			ByteBuffer buffer = ByteBuffer.allocate( samples.length * 4 )
+					.order( ByteOrder.LITTLE_ENDIAN );
 			
-		super.dispose();
+			ShortBuffer shortBuffer = buffer.asShortBuffer();
 
-		if( mOutput != null )
+			if( getMixerChannel() == MixerChannel.LEFT )
-		{
-			mOutput.close();
-		}
-		
-		mOutput = null;
-		mGainControl = null;
-		mMuteControl = null;
-	}
-	
-	private ByteBuffer convert( float[] samples )
-	{
-		/* Little-endian byte buffer */
-		ByteBuffer buffer = ByteBuffer.allocate( samples.length * 4 )
-				.order( ByteOrder.LITTLE_ENDIAN );
-		
-		ShortBuffer shortBuffer = buffer.asShortBuffer();
-
-		if( mMixerChannel == MixerChannel.LEFT )
-		{
-			for( float sample: samples )
 			{
-				shortBuffer.put( (short)( sample * Short.MAX_VALUE ) );
+				for( float sample: samples )
-				shortBuffer.put( (short)0 );
-			}
-		}
-		else
-		{
-			for( float sample: samples )
-			{
-				shortBuffer.put( (short)0 );
-				shortBuffer.put( (short)( sample * Short.MAX_VALUE ) );
-			}
-		}
-		
-		return buffer;
-	}
-	
-	public class QueueProcessor implements Runnable
-	{
-		private AtomicBoolean mProcessing = new AtomicBoolean();
-		
-		public QueueProcessor()
-		{
-		}
-
-		@Override
-		public void run()
-		{
-			try
-			{
-				/* The mProcessing flag ensures that only one instance of the
-				 * processor can run at any given time */
-				if( mProcessing.compareAndSet( false, true ) )
 				{
-					List<AudioPacket> packets = new ArrayList<AudioPacket>();
+					shortBuffer.put( (short)( sample * Short.MAX_VALUE ) );
-					
+					shortBuffer.put( (short)0 );
-					mBuffer.drainTo( packets );
-					
-					if( packets.size() > 0 )
-					{
-						broadcast( mAudioContinuationEvent );
-						
-						for( AudioPacket packet: packets )
-						{
-							if( mCanProcessAudio )
-							{
-								if( isSquelched() )
-								{
-									checkStop();
-								}
-								else if( packet.getType() == Type.AUDIO )
-								{
-									ByteBuffer buffer = convert( 
-											packet.getAudioBuffer().getSamples() );
-									
-									mOutput.write( buffer.array(), 0, 
-											buffer.array().length );
-
-									checkStart();
-									
-									broadcast( packet.getAudioMetadata() );
-									
-									mLastActivity = System.currentTimeMillis();
-								}
-							}
-						}
-					}
-					else
-					{
-						checkStop();
-					}
-					
-					mProcessing.set( false );
 				}
 			}
-			catch( Exception e )
+			else
 			{
-				mLog.error( "Error while processing audio buffers", e );
+				for( float sample: samples )
+				{
+					shortBuffer.put( (short)0 );
+					shortBuffer.put( (short)( sample * Short.MAX_VALUE ) );
+				}
 			}
+			
+			return buffer;
 		}
 		
-		private void checkStart()
+		return null;
-		{
-			if( mCanProcessAudio && !isSquelched() && 
-				!mOutput.isRunning() && mOutput.available() <= START_THRESHOLD )
-			{
-				mOutput.start();
-				
-				mAudioEventBroadcaster.broadcast( mAudioStartEvent );
-			}
-		}
-		
-		private void checkStop()
-		{
-			if( mCanProcessAudio && mOutput.isRunning() &&
-				( mOutput.available() >= STOP_THRESHOLD || isSquelched() ) )
-			{
-				mOutput.drain();
-				mOutput.stop();
-
-				mAudioEventBroadcaster.broadcast( mAudioStopEvent );
-			}
-		}
-	}
-
-	@Override
-	public void setMuted( boolean muted )
-	{
-		if( mMuteControl != null )
-		{
-			mMuteControl.setValue( muted );
-			
-			broadcast( new AudioEvent( muted ? AudioEvent.Type.AUDIO_MUTED : 
-				AudioEvent.Type.AUDIO_UNMUTED, getChannelName() ) );
-		}
-	}
-
-	@Override
-	public boolean isMuted()
-	{
-		if( mMuteControl != null )
-		{
-			return mMuteControl.getValue();
-		}
-		
-		return false;
-	}
-
-	@Override
-	public FloatControl getGainControl()
-	{
-		return mGainControl;
-	}
-
-	@Override
-	public boolean hasGainControl()
-	{
-		return mGainControl != null;
 	}
 }

src/controller/channel/Channel.java

@@ -297,6 +297,9 @@ public class Channel extends Configuration
 
 		/* Broadcast channel deleted event */
 		fireChannelEvent( Event.CHANNEL_DELETED );
+		
+		mProcessingChain.dispose();
+		mProcessingChain = null;
 	}
 	
 	/**
@@ -809,7 +812,7 @@ public class Channel extends Configuration
 	{
 		if( mProcessingChain == null )
 		{
-			mProcessingChain = new ProcessingChain();
+			mProcessingChain = new ProcessingChain( getName() );
 			
 			/* Get the optional alias list for the decode modules to use */
 			AliasList aliasList = mResourceManager.getPlaylistManager()

src/instrument/InstrumentableProcessingChain.java

@@ -12,8 +12,9 @@ import source.Source;
 
 public class InstrumentableProcessingChain extends ProcessingChain implements Instrumentable
 {
-	public InstrumentableProcessingChain()
+	public InstrumentableProcessingChain( String name )
 	{
+		super( name );
 	}
 
 	public void setSource( Source source ) throws IllegalStateException

src/instrument/gui/DecoderViewFrame.java

@@ -99,7 +99,7 @@ public class DecoderViewFrame extends JInternalFrame
 
 		mDecodeConfig = decodeConfig;
 		
-		mProcessingChain = new InstrumentableProcessingChain();
+		mProcessingChain = new InstrumentableProcessingChain( "instrumented" );
 		
 		List<Module> modules = DecoderFactory
 			.getModules( ChannelType.STANDARD, 

src/module/ProcessingChain.java

@@ -19,7 +19,8 @@ package module;
 
 import java.util.ArrayList;
 import java.util.List;
-import java.util.concurrent.ScheduledFuture;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 import message.IMessageListener;
@@ -61,7 +62,7 @@ import audio.metadata.Metadata;
 import audio.squelch.ISquelchStateListener;
 import audio.squelch.ISquelchStateProvider;
 import audio.squelch.SquelchState;
-import controller.ThreadPoolManager;
+import controller.NamingThreadFactory;
 import controller.channel.ChannelEvent;
 import controller.channel.IChannelEventListener;
 import controller.channel.IChannelEventProvider;
@@ -99,15 +100,17 @@ public class ProcessingChain implements IChannelEventListener
 	private Broadcaster<RealBuffer> mRealBufferBroadcaster = new Broadcaster<>();
 	private Broadcaster<SquelchState> mSquelchStateBroadcaster = new Broadcaster<>();
 	
-//	private ThreadPoolManager mThreadPoolManager;
+	private ScheduledExecutorService mScheduledExecutorService;
 	private AtomicBoolean mRunning = new AtomicBoolean();
 	
 	protected Source mSource;
 	private List<Module> mModules = new ArrayList<>();
 	private IFrequencyCorrectionController mFrequencyCorrectionController;
 	
-	public ProcessingChain()
+	public ProcessingChain( String name )
 	{
+		mScheduledExecutorService = Executors.newScheduledThreadPool( 1, 
+				new NamingThreadFactory( "channel " + name ) );
 	}
 
 	public void dispose()
@@ -121,6 +124,9 @@ public class ProcessingChain implements IChannelEventListener
 		
 		mModules.clear();
 		
+		mScheduledExecutorService.shutdownNow();
+		mScheduledExecutorService = null;
+		
 		mFrequencyCorrectionController = null;
 		
 		mAudioPacketBroadcaster.dispose();
@@ -432,9 +438,11 @@ public class ProcessingChain implements IChannelEventListener
 				 * of the decoder state's */
 				if( mSource instanceof TunerChannelSource )
 				{
+					TunerChannelSource tunerChannelSource = (TunerChannelSource)mSource;
+					
 					try
 					{
-						long frequency = ((TunerChannelSource)mSource).getFrequency();
+						long frequency = tunerChannelSource.getFrequency();
 						
 						mDecoderStateEventBroadcaster.broadcast( 
 							new DecoderStateEvent( this, Event.SOURCE_FREQUENCY, 
@@ -444,6 +452,8 @@ public class ProcessingChain implements IChannelEventListener
 					{
 						mLog.error( "Error getting frequency from tuner channel source", e );
 					}
+					
+					tunerChannelSource.start( mScheduledExecutorService );
 				}
 			}
 			else

src/module/decode/ltrstandard/LTRStandardDecoderState.java

@@ -153,7 +153,9 @@ public class LTRStandardDecoderState extends DecoderState
 				case CA_ENDD:
 					CallEndMessage end = (CallEndMessage)message;
 
-					int repeater = end.getHomeRepeater();
+					//Home channel is 31 for call end -- use the free channel
+					//as the call end channel
+					int repeater = end.getFree();
 					
 					mLCNTracker.processCallChannel( repeater );
 					

src/module/decode/p25/P25MessageFramer.java

@@ -289,6 +289,7 @@ public class P25MessageFramer implements Listener<Dibit>
 						else
 						{
 							mComplete = true;
+							dispatch( new P25Message( mMessage.copy(), duid, mAliasList ) );
 						}
 					}
 					else

src/module/decode/p25/P25_C4FMDecoder.java

@@ -77,7 +77,6 @@ public class P25_C4FMDecoder extends P25Decoder implements IRealBufferListener
 		/* Filter demodulated sample buffers */
 		float[] filter = FilterFactory.getLowPass( 48000, 2500, 4000, 80, WindowType.HANNING, true );
 
-		mLog.debug( "Demod Filter tap count:" + filter.length + " coefficients:" + Arrays.toString( filter ) );
 		mC4FMPreFilter = new RealFIRFilter_RB_RB( filter, 1.0f );
 
 		/* Issue tuned frequency correction commands, remotely controlled by the 

src/module/decode/p25/message/tdu/TDUMessage.java

@@ -18,4 +18,19 @@ public class TDUMessage extends P25Message
 	    mCRC = new CRC[ 1 ];
 	    mCRC[ 0 ] = CRC.PASSED;
     }
+	
+	@Override
+    public String getMessage()
+    {
+		StringBuilder sb = new StringBuilder();
+		
+		sb.append( "NAC:" );
+		sb.append( getNAC() );
+		sb.append( " " );
+		sb.append( getDUID().getLabel() );
+		
+		sb.append( " TERMINATOR DATA UNIT" );
+		
+	    return sb.toString();
+    }
 }

src/module/decode/state/ChannelList.java

@@ -22,7 +22,8 @@ import java.awt.Component;
 import java.awt.Point;
 import java.awt.event.MouseEvent;
 import java.awt.event.MouseListener;
-import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 
 import javax.swing.JMenu;
 import javax.swing.JPanel;
@@ -53,8 +54,8 @@ public class ChannelList extends JPanel implements ChannelEventListener
 
 	private final static Logger mLog = LoggerFactory.getLogger( ChannelList.class );
 
-    private HashMap<Channel,ChannelCollectionPanel> mDisplayedPanels = 
+    private Map<Channel,ChannelCollectionPanel> mDisplayedPanels = 
-    			new HashMap<Channel,ChannelCollectionPanel>();
+    			new ConcurrentHashMap<Channel,ChannelCollectionPanel>();
 
     private PlaylistManager mPlaylistManager;
     private SettingsManager mSettingsManager;
@@ -253,20 +254,6 @@ public class ChannelList extends JPanel implements ChannelEventListener
 					idleMenu.add( new ColorSettingResetMenuItem( mSettingsManager, 
 						ColorSettingName.CHANNEL_STATE_GRADIENT_TOP_IDLE ) );
 					
-					JMenu noTunerMenu = new JMenu( "No Tuner" );
-					channelsMenu.add( noTunerMenu );
-					
-					noTunerMenu.add( new ColorSettingMenuItem( mSettingsManager, 
-							ColorSettingName.CHANNEL_STATE_GRADIENT_MIDDLE_NO_TUNER ) );
-					noTunerMenu.add( new ColorSettingResetMenuItem( mSettingsManager, 
-						ColorSettingName.CHANNEL_STATE_GRADIENT_MIDDLE_NO_TUNER ) );
-					noTunerMenu.add( new JSeparator() );	
-					
-					noTunerMenu.add( new ColorSettingMenuItem( mSettingsManager, 
-							ColorSettingName.CHANNEL_STATE_GRADIENT_TOP_NO_TUNER ) );
-					noTunerMenu.add( new ColorSettingResetMenuItem( mSettingsManager, 
-						ColorSettingName.CHANNEL_STATE_GRADIENT_TOP_NO_TUNER ) );
-					
 					JMenu labelMenu = new JMenu( "Labels" );
 					colorMenu.add( labelMenu );
 					

src/module/decode/state/ChannelState.java

@@ -144,11 +144,6 @@ public class ChannelState extends Module implements ICallEventProvider,
 					mMonitoring.set( false );
 				}
 			}
-			else
-			{
-				throw new RuntimeException( "Channel state monitor's scheduled "
-						+ "future pointer was not null" );
-			}
 		}
 	}
 
@@ -388,6 +383,8 @@ public class ChannelState extends Module implements ICallEventProvider,
 	{
 		broadcast( SquelchState.SQUELCH );
 
+		broadcast( new MetadataReset() );
+
 		mState = State.TEARDOWN;
 		
 		broadcast( ChangedAttribute.CHANNEL_STATE );

src/module/decode/state/ChannelStatePanel.java

@@ -202,7 +202,7 @@ public class ChannelStatePanel extends JPanel
 				switch( changedAttribute )
 				{
 					case CHANNEL_STATE:
-						if( state.getState() != null )
+						if( state != null && state.getState() != null )
 						{
 				    		mStateLabel.setText( state.getState().getDisplayValue() );
 						}

src/module/decode/state/TrafficChannelManager.java

@@ -91,6 +91,14 @@ public class TrafficChannelManager extends Module
 	@Override
 	public void dispose()
 	{
+		for( Channel trafficChannel: mTrafficChannelPool )
+		{
+			trafficChannel.setEnabled( false );
+			trafficChannel.dispose();
+		}
+		
+		mTrafficChannelPool.clear();
+		
 		mCallEventListener = null;
 		mResourceManager = null;
 		mDecodeConfiguration = null;

src/settings/SettingsManager.java

@@ -557,11 +557,6 @@ public class SettingsManager
 		ArrayList<TunerConfiguration> configs = getSettings()
 				.getTunerConfigurations( type );
 
-		if( configs.isEmpty() )
-		{
-			configs.add( addNewTunerConfiguration( type, "Default" ) );
-		}
-		
 		return configs;
 	}
 	

src/source/recording/Recording.java

@@ -63,9 +63,8 @@ public class Recording implements Comparable<Recording>,
 	}
 	
 	@Override
-    public TunerChannelSource getChannel( ThreadPoolManager threadPoolManager,
+    public TunerChannelSource getChannel( TunerChannel channel ) 
-            TunerChannel channel ) throws RejectedExecutionException,
+    		throws RejectedExecutionException, SourceException
-            SourceException
     {
 	    // TODO Auto-generated method stub
 	    return null;

src/source/recording/RecordingSourceManager.java

@@ -71,9 +71,7 @@ public class RecordingSourceManager
     		
     		if( recording != null )
     		{
-    			retVal = recording.getChannel( 
+    			retVal = recording.getChannel( tunerChannel );
-    					mResourceManager.getThreadPoolManager(),
-    					tunerChannel );
     		}
     		else
     		{

src/source/tuner/Tuner.java

@@ -30,10 +30,9 @@ import sample.complex.ComplexBuffer;
 import source.SourceException;
 import source.tuner.frequency.FrequencyChangeBroadcaster;
 import source.tuner.frequency.FrequencyChangeEvent;
-import source.tuner.frequency.FrequencyChangeListener;
 import source.tuner.frequency.FrequencyChangeEvent.Event;
+import source.tuner.frequency.FrequencyChangeListener;
 import controller.ResourceManager;
-import controller.ThreadPoolManager;
 
 /**
  * Tuner - provides tuner channel sources, representing a channel frequency
@@ -147,8 +146,8 @@ public abstract class Tuner implements FrequencyChangeBroadcaster,
 	 * 
 	 * @return - source for 48k sample rate
 	 */
-	public abstract TunerChannelSource getChannel( ThreadPoolManager threadPoolManager,
+	public abstract TunerChannelSource getChannel( TunerChannel channel ) 
-		TunerChannel channel ) throws RejectedExecutionException, SourceException;
+			throws RejectedExecutionException, SourceException;
 	
 	/**
 	 * Releases the tuned channel resources

src/source/tuner/TunerChannelProvider.java

@@ -14,8 +14,8 @@ public interface TunerChannelProvider
 	 * 
 	 * @return - source for 48k sample rate
 	 */
-	public abstract TunerChannelSource getChannel( ThreadPoolManager threadPoolManager,
+	public abstract TunerChannelSource getChannel( TunerChannel channel ) 
-		TunerChannel channel ) throws RejectedExecutionException, SourceException;
+			throws RejectedExecutionException, SourceException;
 
 	/**
 	 * Releases the tuned channel resources

src/source/tuner/TunerChannelSource.java

@@ -21,6 +21,7 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.LinkedTransferQueue;
 import java.util.concurrent.RejectedExecutionException;
+import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -37,8 +38,6 @@ import source.SourceException;
 import source.tuner.frequency.FrequencyChangeEvent;
 import source.tuner.frequency.FrequencyChangeEvent.Event;
 import source.tuner.frequency.FrequencyChangeListener;
-import controller.ThreadPoolManager;
-import controller.ThreadPoolManager.ThreadType;
 import dsp.filter.FilterFactory;
 import dsp.filter.Window.WindowType;
 import dsp.filter.cic.ComplexPrimeCICDecimate;
@@ -62,7 +61,6 @@ public class TunerChannelSource extends ComplexSource
 	private ComplexPrimeCICDecimate mDecimationFilter;
 	private Listener<ComplexBuffer> mListener;
 	private FrequencyChangeListener mFrequencyChangeListener;
-	private ThreadPoolManager mThreadPoolManager;
 	private ScheduledFuture<?> mTaskHandle;
 
 	private long mTunerFrequency = 0;
@@ -71,15 +69,11 @@ public class TunerChannelSource extends ComplexSource
 	
 	private DecimationProcessor mDecimationProcessor = new DecimationProcessor();
 	
-	public TunerChannelSource( ThreadPoolManager threadPoolManager,
+	public TunerChannelSource( Tuner tuner, TunerChannel tunerChannel )
-							   Tuner tuner, 
+			   throws RejectedExecutionException, SourceException
-							   TunerChannel tunerChannel )
-				   throws RejectedExecutionException, SourceException
     {
 	    super( "Tuner Channel Source" );
 
-	    mThreadPoolManager = threadPoolManager;
-	    
 	    mTuner = tuner;
 	    mTuner.addListener( (FrequencyChangeListener)this );
 	    
@@ -95,14 +89,17 @@ public class TunerChannelSource extends ComplexSource
 		/* Fire a sample rate change event to setup the decimation chain */
 		frequencyChanged( new FrequencyChangeEvent( 
 			Event.SAMPLE_RATE_CHANGE_NOTIFICATION, mTuner.getSampleRate() ) );
+    }
 	
-		/* Schedule the decimation task to run every 20 ms (50 iterations/second) */
+	public void start( ScheduledExecutorService scheduledExecutorService )
-	    mTaskHandle = mThreadPoolManager.scheduleFixedRate( ThreadType.DECIMATION, 
+	{
-	    		mDecimationProcessor, 20, TimeUnit.MILLISECONDS );
+		/* Schedule the decimation task to run every 10 ms (100 iterations/second) */
+		mTaskHandle = scheduledExecutorService.scheduleAtFixedRate( 
+				    		mDecimationProcessor, 0, 10, TimeUnit.MILLISECONDS );
 
 	    /* Finally, register to receive samples from the tuner */
 		mTuner.addListener( (Listener<ComplexBuffer>)this );
-    }
+	}
 	
     @Override
     public void dispose()
@@ -129,14 +126,15 @@ public class TunerChannelSource extends ComplexSource
     {
 		if( mTaskHandle != null )
 		{
-			mThreadPoolManager.cancel( mTaskHandle );
+			mTaskHandle.cancel( true );
-			mThreadPoolManager = null;
 			mTaskHandle = null;
 		}
 
-
+		synchronized( mBuffer )
-		mBuffer.clear();
+		{
-		mBuffer = null;
+			mBuffer.clear();
+			mBuffer = null;
+		}
 
 		mFrequencyChangeListener = null;
 		mListener = null;
@@ -160,7 +158,13 @@ public class TunerChannelSource extends ComplexSource
 	@Override
     public void receive( ComplexBuffer buffer )
     {
-		mBuffer.add( buffer );
+		synchronized( mBuffer )
+		{
+			if( mBuffer != null )
+			{
+				mBuffer.add( buffer );
+			}
+		}
     }
 
     public void setFrequencyChangeListener( FrequencyChangeListener listener )
@@ -290,7 +294,7 @@ public class TunerChannelSource extends ComplexSource
 			{
 				if( mBuffer != null )
 				{
-					mBuffer.drainTo( mSampleBuffers, 4 );
+					mBuffer.drainTo( mSampleBuffers, 8 );
 			
 					for( Buffer buffer: mSampleBuffers )
 					{

src/source/tuner/TunerController.java

@@ -194,8 +194,8 @@ public abstract class TunerController implements Tunable
 	 * 
 	 * @throws RejectedExecutionException if the decimation processor has an error
 	 */
-	public TunerChannelSource getChannel( ThreadPoolManager threadPoolManager,
+	public TunerChannelSource getChannel( Tuner tuner, TunerChannel channel ) 
-		Tuner tuner, TunerChannel channel ) throws RejectedExecutionException
+			throws RejectedExecutionException
 	{
 		TunerChannelSource source = null;
 		
@@ -210,8 +210,7 @@ public abstract class TunerController implements Tunable
 					updateLOFrequency();
 				}
 				
-				source = new TunerChannelSource( threadPoolManager, 
+				source = new TunerChannelSource( tuner, channel );
-						tuner, channel );
 			}
 			catch( SourceException se )
 			{

src/source/tuner/TunerManager.java

@@ -100,8 +100,7 @@ public class TunerManager
 				
 				try
                 {
-                    retVal = tuner.getChannel( 
+                    retVal = tuner.getChannel( tunerChannel );
-                		mResourceManager.getThreadPoolManager(), tunerChannel );
                 }
 				catch ( RejectedExecutionException ree )
 				{
@@ -545,16 +544,14 @@ public class TunerManager
     			}
     		}
     	}
-    	else
-    	{
-    		config = configs.get( 0 );
-    	}
     	
     	//If we're still null at this point, create a default config
     	if( config == null )
     	{
+    		String name = "Default-" + tuner.getUniqueID();
+    		
     		config = mResourceManager.getSettingsManager()
-				.addNewTunerConfiguration( tuner.getTunerType(), "Default" );
+				.addNewTunerConfiguration( tuner.getTunerType(), name );
     	}
     	
     	//Persist the config as the selected tuner configuration.  The method

src/source/tuner/airspy/AirspyTuner.java

@@ -128,8 +128,8 @@ public class AirspyTuner extends Tuner
 	}
 
 	@Override
-    public TunerChannelSource getChannel( ThreadPoolManager threadPoolManager,
+    public TunerChannelSource getChannel( TunerChannel channel ) 
-		TunerChannel channel ) throws RejectedExecutionException, SourceException
+    		throws RejectedExecutionException, SourceException
     {
 		//TODO: this channel has a decimated sample rate of:
 		// 10.0 MSps = 10,000,000 / 208 = 48076.923
@@ -138,7 +138,7 @@ public class AirspyTuner extends Tuner
 		//Consider implementing a fractional resampler to get a correct 48 kHz
 		//output sample rate
 		
-	    return mController.getChannel( threadPoolManager, this, channel );
+	    return mController.getChannel( this, channel );
     }
 
 	@Override

src/source/tuner/airspy/AirspyTunerController.java

@@ -262,7 +262,30 @@ public class AirspyTunerController extends TunerController
 		}
 	}
 	
-	@Override
+    public static String getTransferStatus( int status )
+	{
+		switch( status )
+		{
+			case 0:
+				return "TRANSFER COMPLETED (0)";
+			case 1:
+				return "TRANSFER ERROR (1)";
+			case 2:
+				return "TRANSFER TIMED OUT (2)";
+			case 3:
+				return "TRANSFER CANCELLED (3)";
+			case 4:
+				return "TRANSFER STALL (4)";
+			case 5:
+				return "TRANSFER NO DEVICE (5)";
+			case 6:
+				return "TRANSFER OVERFLOW (6)";
+			default:
+				return "UNKNOWN TRANSFER STATUS (" + status + ")";
+		}
+	}
+
+    @Override
 	public void apply( TunerConfiguration config ) throws SourceException
 	{
 		if( config instanceof AirspyTunerConfiguration )
@@ -1192,18 +1215,21 @@ public class AirspyTunerController extends TunerController
 	 */
     public void addListener( Listener<ComplexBuffer> listener )
     {
-    	mComplexBufferBroadcaster.addListener( listener );
+    	synchronized( mComplexBufferBroadcaster )
+    	{
+        	mComplexBufferBroadcaster.addListener( listener );
 
-		if( mBufferProcessor == null || !mBufferProcessor.isRunning() )
+    		if( mBufferProcessor == null || !mBufferProcessor.isRunning() )
-		{
+    		{
-			mBufferProcessor = new BufferProcessor();
+    			mBufferProcessor = new BufferProcessor();
 
-			Thread thread = new Thread( mBufferProcessor );
+    			Thread thread = new Thread( mBufferProcessor );
-			thread.setDaemon( true );
+    			thread.setDaemon( true );
-			thread.setName( "Airspy Buffer Processor" );
+    			thread.setName( "Airspy Buffer Processor" );
 
-			thread.start();
+    			thread.start();
-		}
+    		}
+    	}
     }
 
 	/**
@@ -1212,12 +1238,15 @@ public class AirspyTunerController extends TunerController
 	 */
     public void removeListener( Listener<ComplexBuffer> listener )
     {
-    	mComplexBufferBroadcaster.removeListener( listener );
+    	synchronized( mComplexBufferBroadcaster )
+    	{
+        	mComplexBufferBroadcaster.removeListener( listener );
         	
-		if( !mComplexBufferBroadcaster.hasListeners() )
+    		if( !mComplexBufferBroadcaster.hasListeners() )
-		{
+    		{
-			mBufferProcessor.stop();
+    			mBufferProcessor.stop();
-		}
+    		}
+    	}
     }
 	
 	/**
@@ -1227,8 +1256,11 @@ public class AirspyTunerController extends TunerController
 	public class BufferProcessor implements Runnable, TransferCallback
 	{
 		private ScheduledFuture<?> mSampleDispatcherTask;
-        private CopyOnWriteArrayList<Transfer> mTransfers;
+		private LinkedTransferQueue<Transfer> mAvailableTransfers;
+		private LinkedTransferQueue<Transfer> mTransfersInProgress = new LinkedTransferQueue<>();
 		private AtomicBoolean mRunning = new AtomicBoolean();
+		private ByteBuffer mLibUsbHandlerStatus;
+		private boolean mCancel = false;
 
 		@Override
         public void run()
@@ -1237,33 +1269,64 @@ public class AirspyTunerController extends TunerController
 			{
 	            prepareTransfers();
 	            
-				for( Transfer transfer: mTransfers )
-				{
-					int result = LibUsb.submitTransfer( transfer );
-					
-					if( result != LibUsb.SUCCESS )
-					{
-						mLog.error( "error submitting transfer [" + 
-								LibUsb.errorName( result ) + "]" );
-						break;
-					}
-				}
-
 				mSampleDispatcherTask = mThreadPoolManager.scheduleFixedRate( 
 					ThreadType.SOURCE_SAMPLE_PROCESSING, new BufferDispatcher(),
 					20, TimeUnit.MILLISECONDS );
 
+	            mLibUsbHandlerStatus = ByteBuffer.allocateDirect( 4 );
+	            
+				List<Transfer> transfers = new ArrayList<>();
+				
+				mCancel = false;
+				
             	while( mRunning.get() )
 				{
-					ByteBuffer completed = ByteBuffer.allocateDirect( 4 );
+            		mAvailableTransfers.drainTo( transfers );
+            		
+            		for( Transfer transfer: transfers )
+            		{
+    					int result = LibUsb.submitTransfer( transfer );
+    					
+    					if( result == LibUsb.SUCCESS )
+    					{
+    						mTransfersInProgress.add( transfer );
+    					}
+						else
+						{
+    						mLog.error( "error submitting transfer [" + 
+    								LibUsb.errorName( result ) + "]" );
+    					}
+            		}
             		
 					int result = LibUsb.handleEventsTimeoutCompleted( 
-							null, USB_TIMEOUT_MS, completed.asIntBuffer() );
+						null, USB_TIMEOUT_MS, mLibUsbHandlerStatus.asIntBuffer() );
 					
 					if( result != LibUsb.SUCCESS )
 					{
 						mLog.error( "error handling events for libusb" );
 					}
+					
+					transfers.clear();
+					
+					mLibUsbHandlerStatus.rewind();
+				}
+            	
+            	if( mCancel )
+            	{
+            		for( Transfer transfer: mTransfersInProgress )
+            		{
+            			LibUsb.cancelTransfer( transfer );
+            		}
+            		
+            		int result = LibUsb.handleEventsTimeoutCompleted( null,
+        				USB_TIMEOUT_MS, mLibUsbHandlerStatus.asIntBuffer() );
+					
+					if( result != LibUsb.SUCCESS )
+					{
+						mLog.error( "error handling events for libusb" );
+					}
+					
+					mLibUsbHandlerStatus.rewind();
 				}
 			}
         }
@@ -1273,10 +1336,10 @@ public class AirspyTunerController extends TunerController
 		 */
 		public void stop()
 		{
+			mCancel = true;
+			
 			if( mRunning.compareAndSet( true, false ) )
 			{
-				cancel();
-				
 				if( mSampleDispatcherTask != null )
 				{
 					mSampleDispatcherTask.cancel( true );
@@ -1296,97 +1359,68 @@ public class AirspyTunerController extends TunerController
 		@Override
 	    public void processTransfer( Transfer transfer )
 	    {
-			if( transfer.status() == LibUsb.TRANSFER_COMPLETED )
+			mTransfersInProgress.remove( transfer );
-			{
-				ByteBuffer buffer = transfer.buffer();
-				
-				byte[] data = new byte[ transfer.actualLength() ];
-				
-				buffer.get( data );
-
-				buffer.rewind();
-
-				mFilledBuffers.add( data );
-				
-				if( !isRunning() )
-				{
-					LibUsb.cancelTransfer( transfer );
-				}
-			}
 			
 			switch( transfer.status() )
 			{
 				case LibUsb.TRANSFER_COMPLETED:
-					/* resubmit the transfer */
+				case LibUsb.TRANSFER_STALL:
-					int result = LibUsb.submitTransfer( transfer );
+					if( transfer.actualLength() > 0 )
-					
-					if( result != LibUsb.SUCCESS )
 					{
-						mLog.error( "couldn't resubmit buffer transfer to tuner" );
+						ByteBuffer buffer = transfer.buffer();
-						LibUsb.freeTransfer( transfer );
+						
-						mTransfers.remove( transfer );
+						byte[] data = new byte[ transfer.actualLength() ];
+						
+						buffer.get( data );
+		
+						buffer.rewind();
+		
+						if( isRunning() )
+						{
+							mFilledBuffers.add( data );
+						}
 					}
 					break;
 				case LibUsb.TRANSFER_CANCELLED:
-					/* free the transfer and remove it */
-					LibUsb.freeTransfer( transfer );
-					mTransfers.remove( transfer );
 					break;
 				default:
 					/* unexpected error */
-					mLog.error( "transfer error" );
+					mLog.error( "transfer error [" + 
+						getTransferStatus( transfer.status() ) + 
+						"] transferred actual: " + transfer.actualLength() );
 			}
+			
+			mAvailableTransfers.add( transfer );
 	    }
 		
-		private void cancel()
-		{
-			for( Transfer transfer: mTransfers )
-			{
-				LibUsb.cancelTransfer( transfer );
-			}
-
-			ByteBuffer completed = ByteBuffer.allocateDirect( 4 );
-
-			int result = LibUsb.handleEventsTimeoutCompleted( 
-					null, USB_TIMEOUT_MS, completed.asIntBuffer() );
-			
-			if( result != LibUsb.SUCCESS )
-			{
-				mLog.error( "error handling usb events during cancel [" + 
-						LibUsb.errorName( result ) + "]" );
-			}
-		}
-		
 	    /**
 	     * Prepares (allocates) a set of transfer buffers for use in 
 	     * transferring data from the tuner via the bulk interface
 	     */
 	    private void prepareTransfers() throws LibUsbException
 	    {
-	    	mTransfers = new CopyOnWriteArrayList<Transfer>();
+	    	if( mAvailableTransfers == null )
-
-	    	for( int x = 0; x < TRANSFER_BUFFER_POOL_SIZE; x++ )
 	    	{
-	    		Transfer transfer = LibUsb.allocTransfer();
+	    		mAvailableTransfers = new LinkedTransferQueue<>();
 	    		
-	    		if( transfer == null )
+		    	for( int x = 0; x < TRANSFER_BUFFER_POOL_SIZE; x++ )
-	    		{
+		    	{
-	    			throw new LibUsbException( "couldn't allocate transfer", 
+		    		Transfer transfer = LibUsb.allocTransfer();
-	    						LibUsb.ERROR_NO_MEM );
-	    		}
 
-	    		final ByteBuffer buffer = 
+		    		if( transfer == null )
-	    				ByteBuffer.allocateDirect( mBufferSize );
+		    		{
+		    			throw new LibUsbException( "couldn't allocate transfer", 
+		    						LibUsb.ERROR_NO_MEM );
+		    		}
 		    		
-	    		LibUsb.fillBulkTransfer( transfer, 
+		    		final ByteBuffer buffer = 
-	    								 mDeviceHandle, 
+		    				ByteBuffer.allocateDirect( mBufferSize );
-	    								 USB_ENDPOINT, 
-	    								 buffer, 
-	    								 BufferProcessor.this, 
-	    								 "Buffer #" + x,
-	    								 USB_TIMEOUT_MS );
 		    		
-	    		mTransfers.add( transfer );
+		    		LibUsb.fillBulkTransfer( transfer, mDeviceHandle, USB_ENDPOINT, 
+	    				buffer, BufferProcessor.this, "Buffer", USB_TIMEOUT_MS );
+
+		    		mAvailableTransfers.add( transfer );
+		    	}
 	    	}
 	    }
 	}

src/source/tuner/ettus/B100Tuner.java

@@ -99,8 +99,8 @@ public class B100Tuner extends Tuner
     }
 
 	@Override
-    public TunerChannelSource getChannel( ThreadPoolManager threadPoolManager,
+    public TunerChannelSource getChannel( TunerChannel channel ) 
-		TunerChannel channel ) throws RejectedExecutionException, SourceException
+    		throws RejectedExecutionException, SourceException
     {
 		//TODO: pass this call to the tuner controller
 	    return null;

src/source/tuner/fcd/FCDTuner.java

@@ -112,11 +112,10 @@ public class FCDTuner extends MixerTuner
     }
 
 	@Override
-    public TunerChannelSource getChannel( ThreadPoolManager threadPoolManager,
+    public TunerChannelSource getChannel( TunerChannel tunerChannel )	
-    	TunerChannel tunerChannel )	throws RejectedExecutionException, 
+    		throws RejectedExecutionException, SourceException
-    									   SourceException
     {
-		return mController.getChannel( threadPoolManager, this, tunerChannel );
+		return mController.getChannel( this, tunerChannel );
     }
 
 	/**

src/source/tuner/hackrf/HackRFTuner.java

@@ -106,10 +106,10 @@ public class HackRFTuner extends Tuner
     }
 
 	@Override
-    public TunerChannelSource getChannel( ThreadPoolManager threadPoolManager,
+    public TunerChannelSource getChannel( TunerChannel channel ) 
-		TunerChannel channel ) throws RejectedExecutionException, SourceException
+    		throws RejectedExecutionException, SourceException
     {
-	    return mController.getChannel( threadPoolManager, this, channel );
+	    return mController.getChannel( this, channel );
     }
 
 	@Override

src/source/tuner/hackrf/HackRFTunerController.java

@@ -56,6 +56,7 @@ import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.LinkedTransferQueue;
 import java.util.concurrent.ScheduledFuture;
@@ -91,7 +92,7 @@ public class HackRFTunerController extends TunerController
 	private final static Logger mLog = 
 			LoggerFactory.getLogger( HackRFTunerController.class );
 
-	public final static long TIMEOUT_US = 1000000l; //uSeconds
+	public final static long USB_TIMEOUT_MS = 1000000l; //uSeconds
 	public static final byte USB_ENDPOINT = (byte)0x81;
 	public static final byte USB_INTERFACE = (byte)0x0;
 	
@@ -394,7 +395,7 @@ public class HackRFTunerController extends TunerController
 													  (short)value,
 													  (short)index,
 													  buffer, 
-													  TIMEOUT_US );
+													  USB_TIMEOUT_MS );
 
 			if( transferred < 0 )
 			{
@@ -467,7 +468,7 @@ public class HackRFTunerController extends TunerController
 													  (short)value, 
 													  (short)index, 
 													  buffer, 
-													  TIMEOUT_US );
+													  USB_TIMEOUT_MS );
 
 			if( transferred < 0 )
 			{
@@ -886,18 +887,21 @@ public class HackRFTunerController extends TunerController
 	 */
     public void addListener( Listener<ComplexBuffer> listener )
     {
-    	mComplexBufferBroadcaster.addListener( listener );
+    	synchronized( mComplexBufferBroadcaster )
+    	{
+        	mComplexBufferBroadcaster.addListener( listener );
 
-		if( mBufferProcessor == null || !mBufferProcessor.isRunning() )
+    		if( mBufferProcessor == null || !mBufferProcessor.isRunning() )
-		{
+    		{
-			mBufferProcessor = new BufferProcessor();
+    			mBufferProcessor = new BufferProcessor();
 
-			Thread thread = new Thread( mBufferProcessor );
+    			Thread thread = new Thread( mBufferProcessor );
-			thread.setDaemon( true );
+    			thread.setDaemon( true );
-			thread.setName( "HackRF Sample Processor" );
+    			thread.setName( "HackRF Sample Processor" );
 
-			thread.start();
+    			thread.start();
-		}
+    		}
+    	}
     }
 
 	/**
@@ -906,12 +910,15 @@ public class HackRFTunerController extends TunerController
 	 */
     public void removeListener( Listener<ComplexBuffer> listener )
     {
-    	mComplexBufferBroadcaster.removeListener( listener );
+    	synchronized( mComplexBufferBroadcaster )
+    	{
+        	mComplexBufferBroadcaster.removeListener( listener );
         	
-		if( !mComplexBufferBroadcaster.hasListeners() )
+    		if( !mComplexBufferBroadcaster.hasListeners() )
-		{
+    		{
-			mBufferProcessor.stop();
+    			mBufferProcessor.stop();
-		}
+    		}
+    	}
     }
 
 	/**
@@ -921,45 +928,77 @@ public class HackRFTunerController extends TunerController
 	public class BufferProcessor implements Runnable, TransferCallback
 	{
 		private ScheduledFuture<?> mSampleDispatcherTask;
-        private CopyOnWriteArrayList<Transfer> mTransfers;
+		private LinkedTransferQueue<Transfer> mAvailableTransfers;
+		private LinkedTransferQueue<Transfer> mTransfersInProgress = new LinkedTransferQueue<>();
 		private AtomicBoolean mRunning = new AtomicBoolean();
+		private ByteBuffer mLibUsbHandlerStatus;
+		private boolean mCancel = false;
 
 		@Override
         public void run()
         {
 			if( mRunning.compareAndSet( false, true ) )
 			{
-				mLog.info( "starting HackRF sample fetch thread" );
-
 	            prepareTransfers();
 	            
-				for( Transfer transfer: mTransfers )
-				{
-					int result = LibUsb.submitTransfer( transfer );
-					
-					if( result != LibUsb.SUCCESS )
-					{
-						mLog.error( "error submitting transfer [" + 
-								LibUsb.errorName( result ) + "]" );
-						break;
-					}
-				}
-
 				mSampleDispatcherTask = mThreadPoolManager.scheduleFixedRate( 
 					ThreadType.SOURCE_SAMPLE_PROCESSING, new BufferDispatcher(),
 					20, TimeUnit.MILLISECONDS );
 
+				mLibUsbHandlerStatus = ByteBuffer.allocateDirect( 4 );
+				
+				List<Transfer> transfers = new ArrayList<>();
+				
+				mCancel = false;
+				
             	while( mRunning.get() )
 				{
-					ByteBuffer completed = ByteBuffer.allocateDirect( 4 );
+            		mAvailableTransfers.drainTo( transfers );
+            		
+    				for( Transfer transfer: transfers )
+    				{
+    					int result = LibUsb.submitTransfer( transfer );
+    					
+    					if( result == LibUsb.SUCCESS )
+    					{
+    						mTransfersInProgress.add( transfer );
+    					}
+    					else
+    					{
+    						mLog.error( "error submitting transfer [" + 
+    								LibUsb.errorName( result ) + "]" );
+    					}
+    				}
 					
 					int result = LibUsb.handleEventsTimeoutCompleted( 
-							null, TIMEOUT_US, completed.asIntBuffer() );
+							null, USB_TIMEOUT_MS, mLibUsbHandlerStatus.asIntBuffer() );
 					
 					if( result != LibUsb.SUCCESS )
 					{
 						mLog.error( "error handling events for libusb" );
 					}
+					
+					transfers.clear();
+					
+					mLibUsbHandlerStatus.rewind();
+				}
+            	
+            	if( mCancel )
+            	{
+            		for( Transfer transfer: mTransfersInProgress )
+            		{
+            			LibUsb.cancelTransfer( transfer );
+            		}
+            		
+					int result = LibUsb.handleEventsTimeoutCompleted( 
+						null, USB_TIMEOUT_MS, mLibUsbHandlerStatus.asIntBuffer() );
+            		
+            		if( result != LibUsb.SUCCESS )
+					{
+						mLog.error( "error cancelling transfers in progress" );
+					}
+					
+					mLibUsbHandlerStatus.rewind();
 				}
 			}
         }
@@ -969,12 +1008,10 @@ public class HackRFTunerController extends TunerController
 		 */
 		public void stop()
 		{
+			mCancel = true;
+			
 			if( mRunning.compareAndSet( true, false ) )
 			{
-				mLog.info( "stopping HackRF sample fetch thread" );
-
-				cancel();
-				
 				if( mSampleDispatcherTask != null )
 				{
 					mSampleDispatcherTask.cancel( true );
@@ -994,41 +1031,29 @@ public class HackRFTunerController extends TunerController
 		@Override
 	    public void processTransfer( Transfer transfer )
 	    {
-			if( transfer.status() == LibUsb.TRANSFER_COMPLETED )
+			mTransfersInProgress.remove( transfer );
-			{
-				ByteBuffer buffer = transfer.buffer();
-				
-				byte[] data = new byte[ transfer.actualLength() ];
-				
-				buffer.get( data );
-
-				buffer.rewind();
-
-				mFilledBuffers.add( data );
-				
-				if( !isRunning() )
-				{
-					LibUsb.cancelTransfer( transfer );
-				}
-			}
 			
 			switch( transfer.status() )
 			{
 				case LibUsb.TRANSFER_COMPLETED:
-					/* resubmit the transfer */
+				case LibUsb.TRANSFER_STALL:
-					int result = LibUsb.submitTransfer( transfer );
+					if( transfer.actualLength() > 0 )
-					
-					if( result != LibUsb.SUCCESS )
 					{
-						mLog.error( "couldn't resubmit buffer transfer to tuner" );
+						ByteBuffer buffer = transfer.buffer();
-						LibUsb.freeTransfer( transfer );
+						
-						mTransfers.remove( transfer );
+						byte[] data = new byte[ transfer.actualLength() ];
+						
+						buffer.get( data );
+
+						buffer.rewind();
+
+						if( isRunning() )
+						{
+							mFilledBuffers.add( data );
+						}
 					}
 					break;
 				case LibUsb.TRANSFER_CANCELLED:
-					/* free the transfer and remove it */
-					LibUsb.freeTransfer( transfer );
-					mTransfers.remove( transfer );
 					break;
 				default:
 					/* unexpected error */
@@ -1036,57 +1061,38 @@ public class HackRFTunerController extends TunerController
 						getTransferStatus( transfer.status() ) + 
 						"] transferred actual: " + transfer.actualLength() );
 			}
+			
+			mAvailableTransfers.add( transfer );
 	    }
 		
-		private void cancel()
-		{
-			for( Transfer transfer: mTransfers )
-			{
-				LibUsb.cancelTransfer( transfer );
-			}
-
-			ByteBuffer completed = ByteBuffer.allocateDirect( 4 );
-
-			int result = LibUsb.handleEventsTimeoutCompleted( 
-					null, TIMEOUT_US, completed.asIntBuffer() );
-			
-			if( result != LibUsb.SUCCESS )
-			{
-				mLog.error( "error handling usb events during cancel [" + 
-						LibUsb.errorName( result ) + "]" );
-			}
-		}
-		
 	    /**
 	     * Prepares (allocates) a set of transfer buffers for use in 
 	     * transferring data from the tuner via the bulk interface
 	     */
 	    private void prepareTransfers() throws LibUsbException
 	    {
-	    	mTransfers = new CopyOnWriteArrayList<Transfer>();
+	    	if( mAvailableTransfers == null )
-
-	    	for( int x = 0; x < TRANSFER_BUFFER_POOL_SIZE; x++ )
 	    	{
-	    		Transfer transfer = LibUsb.allocTransfer();
+	    		mAvailableTransfers = new LinkedTransferQueue<>();
 	    		
-	    		if( transfer == null )
+		    	for( int x = 0; x < TRANSFER_BUFFER_POOL_SIZE; x++ )
-	    		{
+		    	{
-	    			throw new LibUsbException( "couldn't allocate transfer", 
+		    		Transfer transfer = LibUsb.allocTransfer();
-	    						LibUsb.ERROR_NO_MEM );
-	    		}
 
-	    		final ByteBuffer buffer = 
+		    		if( transfer == null )
-	    				ByteBuffer.allocateDirect( mBufferSize );
+		    		{
+		    			throw new LibUsbException( "couldn't allocate transfer", 
+		    						LibUsb.ERROR_NO_MEM );
+		    		}
 		    		
-	    		LibUsb.fillBulkTransfer( transfer, 
+		    		final ByteBuffer buffer = 
-	    								 mDeviceHandle, 
+		    				ByteBuffer.allocateDirect( mBufferSize );
-	    								 USB_ENDPOINT, 
-	    								 buffer, 
-	    								 BufferProcessor.this, 
-	    								 "Buffer #" + x,
-	    								 TIMEOUT_US );
 		    		
-	    		mTransfers.add( transfer );
+		    		LibUsb.fillBulkTransfer( transfer, mDeviceHandle,USB_ENDPOINT, 
+	    				buffer, BufferProcessor.this, "Buffer", USB_TIMEOUT_MS );
+
+		    		mAvailableTransfers.add( transfer );
+		    	}
 	    	}
 	    }
 	}

src/source/tuner/rtl/RTL2832Tuner.java

@@ -37,7 +37,6 @@ import source.tuner.TunerType;
 import source.tuner.frequency.FrequencyChangeListener;
 import source.tuner.rtl.RTL2832TunerController.SampleRate;
 import controller.ResourceManager;
-import controller.ThreadPoolManager;
 
 public class RTL2832Tuner extends Tuner
 {
@@ -148,16 +147,14 @@ public class RTL2832Tuner extends Tuner
 	}
 
 	@Override
-    public TunerChannelSource getChannel( ThreadPoolManager threadPoolManager,
+    public TunerChannelSource getChannel( TunerChannel channel )
-    									  TunerChannel channel )
+    		throws RejectedExecutionException, SourceException
-    									    throws RejectedExecutionException,
-    									    	   SourceException
 	{
 		TunerChannelSource source = null;
 		
 		try
 		{
-			source = mController.getChannel( threadPoolManager, this, channel );
+			source = mController.getChannel( this, channel );
 		}
 		catch( Exception e )
 		{

src/source/tuner/rtl/RTL2832TunerController.java

@@ -27,7 +27,7 @@ import java.nio.charset.Charset;
 import java.text.DecimalFormat;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.List;
 import java.util.concurrent.LinkedTransferQueue;
 import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.TimeUnit;
@@ -55,8 +55,6 @@ import sample.complex.ComplexBuffer;
 import source.SourceException;
 import source.tuner.TunerController;
 import source.tuner.TunerType;
-import source.tuner.frequency.FrequencyChangeEvent;
-import source.tuner.frequency.FrequencyChangeEvent.Event;
 import buffer.FloatAveragingBuffer;
 import controller.ResourceManager;
 import controller.ThreadPoolManager;
@@ -73,7 +71,7 @@ public abstract class RTL2832TunerController extends TunerController
 	public final static int TWO_TO_22_POWER = 4194304;
 	
 	public final static byte USB_INTERFACE = (byte)0x0;
-	public final static byte BULK_ENDPOINT_IN = (byte)0x81;
+	public final static byte USB_BULK_ENDPOINT = (byte)0x81;
 	public final static byte CONTROL_ENDPOINT_IN = 
 			(byte)( LibUsb.ENDPOINT_IN | LibUsb.REQUEST_TYPE_VENDOR );
 	public final static byte CONTROL_ENDPOINT_OUT = 
@@ -1342,21 +1340,24 @@ public abstract class RTL2832TunerController extends TunerController
 	 */
     public void addListener( Listener<ComplexBuffer> listener )
     {
-		mComplexBufferBroadcaster.addListener( listener );
+    	synchronized( mComplexBufferBroadcaster )
+    	{
+    		mComplexBufferBroadcaster.addListener( listener );
 
-		if( mBufferProcessor == null )
+    		if( mBufferProcessor == null )
-		{
+    		{
-			mBufferProcessor = new BufferProcessor( mThreadPoolManager );
+    			mBufferProcessor = new BufferProcessor( mThreadPoolManager );
-		}
+    		}
     		
-		if( !mBufferProcessor.isRunning() )
+    		if( !mBufferProcessor.isRunning() )
-		{
+    		{
-			Thread thread = new Thread( mBufferProcessor );
+    			Thread thread = new Thread( mBufferProcessor );
-			thread.setDaemon( true );
+    			thread.setDaemon( true );
-			thread.setName( "RTL2832 Sample Processor" );
+    			thread.setName( "RTL2832 Sample Processor" );
 
-			thread.start();
+    			thread.start();
-		}
+    		}
+    	}
     }
 
 	/**
@@ -1365,12 +1366,15 @@ public abstract class RTL2832TunerController extends TunerController
 	 */
     public void removeListener( Listener<ComplexBuffer> listener )
     {
-    	mComplexBufferBroadcaster.removeListener( listener );
+    	synchronized( mComplexBufferBroadcaster )
+    	{
+        	mComplexBufferBroadcaster.removeListener( listener );
 
-		if( !mComplexBufferBroadcaster.hasListeners() )
+    		if( !mComplexBufferBroadcaster.hasListeners() )
-		{
+    		{
-			mBufferProcessor.stop();
+    			mBufferProcessor.stop();
-		}
+    		}
+    	}
     }
 
 	/**
@@ -1380,9 +1384,12 @@ public abstract class RTL2832TunerController extends TunerController
 	public class BufferProcessor implements Runnable, TransferCallback
 	{
 		private ScheduledFuture<?> mSampleDispatcherTask;
-        private CopyOnWriteArrayList<Transfer> mTransfers;
+		private LinkedTransferQueue<Transfer> mAvailableTransfers;
+		private LinkedTransferQueue<Transfer> mTransfersInProgress = new LinkedTransferQueue<>();
 		private AtomicBoolean mRunning = new AtomicBoolean();
 		private ThreadPoolManager mThreadPoolManager;
+		private ByteBuffer mLibUsbHandlerStatus;
+		private boolean mCancel = false;
 
 		public BufferProcessor( ThreadPoolManager manager )
 		{
@@ -1409,18 +1416,6 @@ public abstract class RTL2832TunerController extends TunerController
 
 	            prepareTransfers();
 	            
-				for( Transfer transfer: mTransfers )
-				{
-					int result = LibUsb.submitTransfer( transfer );
-					
-					if( result != LibUsb.SUCCESS )
-					{
-						mLog.error( "error submitting transfer [" + 
-								LibUsb.errorName( result ) + "]" );
-						break;
-					}
-				}
-
 				try
 				{
 					mSampleDispatcherTask = mThreadPoolManager.scheduleFixedRate( 
@@ -1432,19 +1427,65 @@ public abstract class RTL2832TunerController extends TunerController
 					mLog.error( "NPE! = tpm null: " + ( mThreadPoolManager == null ), npe );
 				}
 
+				mLibUsbHandlerStatus = ByteBuffer.allocateDirect( 4 );
 				
-            	while( mRunning.get() )
+				List<Transfer> transfers = new ArrayList<>();
+
+				mCancel = false;
+				
+				while( mRunning.get() )
 				{
-					ByteBuffer completed = ByteBuffer.allocateDirect( 4 );
+            		mAvailableTransfers.drainTo( transfers );
+
+            		for( Transfer transfer: transfers )
+            		{
+            			int result = LibUsb.submitTransfer( transfer );
+            			
+            			if( result == LibUsb.SUCCESS )
+            			{
+            				mTransfersInProgress.add( transfer );
+            			}
+            			else
+            			{
+            				mLog.error( "Error submitting transfer [" + 
+            						LibUsb.errorName( result ) + "]" );
+            			}
+            		}
             		
 					int result = LibUsb.handleEventsTimeoutCompleted( 
-							null, TIMEOUT_US, completed.asIntBuffer() );
+							null, TIMEOUT_US, mLibUsbHandlerStatus.asIntBuffer() );
 					
 					if( result != LibUsb.SUCCESS )
 					{
 						mLog.error( "error handling events for libusb" );
 					}
+					
+					transfers.clear();
+					
+					mLibUsbHandlerStatus.rewind();
 				}
+            	
+            	if( mCancel )
+            	{
+            		for( Transfer transfer: mTransfersInProgress )
+            		{
+            			LibUsb.cancelTransfer( transfer );
+            		}
+            		
+					int result = LibUsb.handleEventsTimeoutCompleted( 
+							null, TIMEOUT_US, mLibUsbHandlerStatus.asIntBuffer() );
+					
+					if( result != LibUsb.SUCCESS )
+					{
+						mLog.error( "error handling events for libusb" );
+					}
+					
+					mLibUsbHandlerStatus.rewind();
+            	}
+			}
+			else
+			{
+				mLog.error( "Couldn't start buffer processor - already running!" );
 			}
         }
 
@@ -1453,10 +1494,10 @@ public abstract class RTL2832TunerController extends TunerController
 		 */
 		public void stop()
 		{
+			mCancel = true;
+			
 			if( mRunning.compareAndSet( true, false ) )
 			{
-				cancel();
-				
 				if( mSampleDispatcherTask != null )
 				{
 					mThreadPoolManager.cancel( mSampleDispatcherTask );
@@ -1477,43 +1518,29 @@ public abstract class RTL2832TunerController extends TunerController
 		@Override
 	    public void processTransfer( Transfer transfer )
 	    {
-			if( transfer.status() == LibUsb.TRANSFER_COMPLETED )
+			mTransfersInProgress.remove( transfer );
-			{
-				ByteBuffer buffer = transfer.buffer();
-				
-				byte[] data = new byte[ transfer.actualLength() ];
-				
-				buffer.get( data );
-
-				buffer.rewind();
-
-				mFilledBuffers.add( data );
-				
-				mSampleCounter.addAndGet( transfer.actualLength() );
-				
-				if( !isRunning() )
-				{
-					LibUsb.cancelTransfer( transfer );
-				}
-			}
 			
 			switch( transfer.status() )
 			{
 				case LibUsb.TRANSFER_COMPLETED:
-					/* resubmit the transfer */
+				case LibUsb.TRANSFER_STALL:
-					int result = LibUsb.submitTransfer( transfer );
+					if( transfer.actualLength() > 0 )
-					
-					if( result != LibUsb.SUCCESS )
 					{
-						mLog.error( "couldn't resubmit buffer transfer to tuner" );
+						ByteBuffer buffer = transfer.buffer();
-						LibUsb.freeTransfer( transfer );
+						
-						mTransfers.remove( transfer );
+						byte[] data = new byte[ transfer.actualLength() ];
+						
+						buffer.get( data );
+
+						buffer.rewind();
+
+						if( isRunning() )
+						{
+							mFilledBuffers.add( data );
+						}
 					}
 					break;
 				case LibUsb.TRANSFER_CANCELLED:
-					/* free the transfer and remove it */
-					LibUsb.freeTransfer( transfer );
-					mTransfers.remove( transfer );
 					break;
 				default:
 					/* unexpected error */
@@ -1521,57 +1548,38 @@ public abstract class RTL2832TunerController extends TunerController
 						getTransferStatus( transfer.status() ) + 
 						"] transferred actual: " + transfer.actualLength() );
 			}
+			
+			mAvailableTransfers.add( transfer );
 	    }
 		
-		private void cancel()
-		{
-			for( Transfer transfer: mTransfers )
-			{
-				LibUsb.cancelTransfer( transfer );
-			}
-
-			ByteBuffer completed = ByteBuffer.allocateDirect( 4 );
-
-			int result = LibUsb.handleEventsTimeoutCompleted( 
-					null, TIMEOUT_US, completed.asIntBuffer() );
-			
-			if( result != LibUsb.SUCCESS )
-			{
-				mLog.error( "error handling usb events during cancel [" + 
-						LibUsb.errorName( result ) + "]" );
-			}
-		}
-		
 	    /**
 	     * Prepares (allocates) a set of transfer buffers for use in 
 	     * transferring data from the tuner via the bulk interface
 	     */
 	    private void prepareTransfers() throws LibUsbException
 	    {
-	    	mTransfers = new CopyOnWriteArrayList<Transfer>();
+	    	if( mAvailableTransfers == null )
-
-	    	for( int x = 0; x < TRANSFER_BUFFER_POOL_SIZE; x++ )
 	    	{
-	    		Transfer transfer = LibUsb.allocTransfer();
+	    		mAvailableTransfers = new LinkedTransferQueue<>();
 	    		
-	    		if( transfer == null )
+		    	for( int x = 0; x < TRANSFER_BUFFER_POOL_SIZE; x++ )
-	    		{
+		    	{
-	    			throw new LibUsbException( "couldn't allocate transfer", 
+		    		Transfer transfer = LibUsb.allocTransfer();
-	    						LibUsb.ERROR_NO_MEM );
-	    		}
 
-	    		final ByteBuffer buffer = 
+		    		if( transfer == null )
-	    				ByteBuffer.allocateDirect( mBufferSize );
+		    		{
+		    			throw new LibUsbException( "couldn't allocate transfer", 
+		    						LibUsb.ERROR_NO_MEM );
+		    		}
 		    		
-	    		LibUsb.fillBulkTransfer( transfer, 
+		    		final ByteBuffer buffer = 
-	    								 mDeviceHandle, 
+		    				ByteBuffer.allocateDirect( mBufferSize );
-	    								 BULK_ENDPOINT_IN, 
-	    								 buffer, 
-	    								 BufferProcessor.this, 
-	    								 "Buffer #" + x,
-	    								 TIMEOUT_US );
 		    		
-	    		mTransfers.add( transfer );
+		    		LibUsb.fillBulkTransfer( transfer, mDeviceHandle, USB_BULK_ENDPOINT, 
+		    				buffer, BufferProcessor.this, "Buffer", TIMEOUT_US );
+
+		    		mAvailableTransfers.add( transfer );
+		    	}
 	    	}
 	    }
 	}

src/source/tuner/rtl/r820t/R820TTunerConfiguration.java

@@ -34,7 +34,7 @@ public class R820TTunerConfiguration extends TunerConfiguration
 	private R820TLNAGain mLNAGain = R820TLNAGain.GAIN_222;
 	private R820TVGAGain mVGAGain = R820TVGAGain.GAIN_210;
 	private double mFrequencyCorrection = 0.0d;
-	private SampleRate mSampleRate = SampleRate.RATE_1_920MHZ;
+	private SampleRate mSampleRate = SampleRate.RATE_2_400MHZ;
 
 	/**
 	 * Default constructor for JAXB

src/spectrum/DFTProcessor.java

@@ -20,6 +20,7 @@ package spectrum;
 import java.util.Arrays;
 import java.util.Iterator;
 import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
@@ -56,8 +57,12 @@ public class DFTProcessor implements Listener<ComplexBuffer>,
 	private CopyOnWriteArrayList<DFTResultsConverter> mListeners =
 			new CopyOnWriteArrayList<DFTResultsConverter>();
 
-	private ArrayBlockingQueue<ComplexBuffer> mQueue = 
+	//Fixed size sample queue.  We set the size at 12 based on the highest
-			new ArrayBlockingQueue<ComplexBuffer>( 200 );
+	//sample rate tuner (10 MHz) producing 153 frames per second and the lowest
+	//DFT processing frame rate of 12 frames per second.  This means that the 
+	//maximum size needed is 153 / 12 = 11 frames per DFT processing iteration
+	//so we set it at 12.
+	private BlockingQueue<ComplexBuffer> mQueue = new ArrayBlockingQueue<>( 12 );
 							
 	private ScheduledExecutorService mScheduler = Executors
 			.newScheduledThreadPool( 1, new NamingThreadFactory( "spectrum dft" ) );	
@@ -246,15 +251,7 @@ public class DFTProcessor implements Listener<ComplexBuffer>,
 	@Override
     public void receive( ComplexBuffer sampleBuffer )
     {
-		if( !mQueue.offer( sampleBuffer ) )
+		mQueue.offer( sampleBuffer );
-		{
-			mLog.error( "DFTProcessor - [" + mSampleType.toString()
-						+ "] queue is full, purging queue, "
-						+ "samples[" + sampleBuffer + "]" );
-
-			mQueue.clear();
-			mQueue.offer( sampleBuffer );
-		}
     }
 	
 	private void getNextBuffer()