IQ recording file playback partial checkin.

NOTE: only the gui components and settings handling have been implemented.  Actual recording playback is not yet implemented.

Partial checkin of initial P25 decoder development.  

NOTE: P25 decoder is not yet functional.

src/decode/p25/P25Decoder.java

@@ -0,0 +1,144 @@
+/*******************************************************************************
+ *     SDR Trunk 
+ *     Copyright (C) 2014 Dennis Sheirer
+ * 
+ *     This program is free software: you can redistribute it and/or modify
+ *     it under the terms of the GNU General Public License as published by
+ *     the Free Software Foundation, either version 3 of the License, or
+ *     (at your option) any later version.
+ * 
+ *     This program is distributed in the hope that it will be useful,
+ *     but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *     GNU General Public License for more details.
+ * 
+ *     You should have received a copy of the GNU General Public License
+ *     along with this program.  If not, see <http://www.gnu.org/licenses/>
+ ******************************************************************************/
+package decode.p25;
+
+import instrument.Instrumentable;
+import instrument.tap.Tap;
+import instrument.tap.stream.FloatTap;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import source.Source.SampleType;
+import alias.AliasList;
+import decode.Decoder;
+import decode.DecoderType;
+import dsp.filter.DCRemovalFilter2;
+import dsp.fsk.C4FMDecoder;
+import dsp.nbfm.FilteringNBFMDemodulator;
+
+public class P25Decoder extends Decoder implements Instrumentable
+{
+	/**
+	 * This value determines how quickly the DC remove filter responds to 
+	 * changes in frequency.
+	 */
+	private static final double sDC_REMOVAL_RATIO = 0.000003;
+
+	private final String TAP_DEMOD_TO_DECODER = "Demodulated Audio <> C4FM Decoder";
+	
+	private FilteringNBFMDemodulator mDemodulator;
+	private DCRemovalFilter2 mDCRemovalFilter; 
+	private C4FMDecoder mC4FMDecoder;
+	private AliasList mAliasList;
+	
+	private ArrayList<Tap> mTaps;
+	
+	public P25Decoder( SampleType sampleType, AliasList aliasList )
+	{
+		super( sampleType );
+		
+		mAliasList = aliasList;
+		
+		/**
+		 * Only setup a demod chain if we're receiving complex samples.  If
+		 * we're receiving demodulated samples, they'll be handled the same 
+		 * way as we handle the output of the demodulator.
+		 */
+		if( mSourceSampleType == SampleType.COMPLEX )
+		{
+			/**
+			 * The Decoder super class is both a Complex listener and a float
+			 * listener.  So, we add the demod to listen to the incoming 
+			 * quadrature samples, and we wire the output of the demod right
+			 * back to this class, so we can receive the demodulated output
+			 * to process
+			 */
+			mDemodulator = new FilteringNBFMDemodulator();
+			this.addComplexListener( mDemodulator );
+
+			/**
+			 * Remove the DC component that is present when we're mistuned
+			 */
+			mDCRemovalFilter = new DCRemovalFilter2( sDC_REMOVAL_RATIO );
+			mDemodulator.addListener( mDCRemovalFilter );
+
+			/**
+			 * Route the demodulated, filtered samples back to this class to send
+			 * to all registered listeners
+			 */
+			mDCRemovalFilter.setListener( this.getFloatReceiver() );
+			
+		}
+
+		mC4FMDecoder = new C4FMDecoder();
+		addFloatListener( mC4FMDecoder );
+	}
+
+	@Override
+    public DecoderType getType()
+    {
+	    return DecoderType.NBFM;
+    }
+
+	@Override
+    public List<Tap> getTaps()
+    {
+		if( mTaps == null )
+		{
+			mTaps = new ArrayList<Tap>();
+			mTaps.add( new FloatTap( TAP_DEMOD_TO_DECODER, 0, 1.0f ) );
+			
+			mTaps.addAll( mC4FMDecoder.getTaps() );
+		}
+		
+	    return mTaps;
+    }
+
+	@Override
+    public void addTap( Tap tap )
+    {
+		mC4FMDecoder.addTap( tap );
+		
+		switch( tap.getName() )
+		{
+			case TAP_DEMOD_TO_DECODER:
+				FloatTap demodTap = (FloatTap)tap;
+				removeFloatListener( mC4FMDecoder );
+				addFloatListener( demodTap );
+				demodTap.setListener( mC4FMDecoder );
+				break;
+		}
+    }
+
+	@Override
+    public void removeTap( Tap tap )
+    {
+		mC4FMDecoder.removeTap( tap );
+		
+		switch( tap.getName() )
+		{
+			case TAP_DEMOD_TO_DECODER:
+				FloatTap demodTap = (FloatTap)tap;
+				removeFloatListener( demodTap );
+				demodTap.removeListener( mC4FMDecoder );
+				addFloatListener( mC4FMDecoder );
+				break;
+		}
+    }
+}