Changes audio module decimation filter from lowpass to bandpass so that we can remove 0-250 Hz and any LTR signalling from the audio output.

src/audio/AudioModule.java

@@ -46,15 +46,15 @@ public class AudioModule extends Module implements IAudioPacketProvider,
 
     static
     {
-        FIRFilterSpecification specification = FIRFilterSpecification.lowPassBuilder()
-                .sampleRate(48000)
-                .gridDensity(16)
-                .passBandCutoff(3000)
-                .passBandAmplitude(1.0)
-                .passBandRipple(0.01)
-                .stopBandStart(4000)
-                .stopBandAmplitude(0.0)
-                .stopBandRipple(0.027)
+        //Band-pass filter to both decimate (48kHz to 8kHz) and block 0 - 300 Hz (LTR signalling).
+        FIRFilterSpecification specification = FIRFilterSpecification.bandPassBuilder()
+                .sampleRate( 48000 )
+                .stopFrequency1( 150 )
+                .passFrequencyBegin( 300 )
+                .passFrequencyEnd( 3500 )
+                .stopFrequency2( 4000 )
+                .stopRipple( 0.0004 )
+                .passRipple( 0.008)
                 .build();
 
         RemezFIRFilterDesigner designer = new RemezFIRFilterDesigner(specification);
@@ -86,16 +86,12 @@ public class AudioModule extends Module implements IAudioPacketProvider,
     private Listener<AudioPacket> mAudioPacketListener;
     private PolyphaseFIRDecimatingFilter_RB mAudioDecimationFilter;
 
-    //TODO: remove this -- is being replaced by the DemodulatedAudioFilterModule
-    private RealFIRFilter_R_R mAudioFilter = new RealFIRFilter_R_R(
-            Filters.FIR_BANDPASS_AUDIO_48KHZ.getCoefficients(), 2.0f);
-
     public AudioModule(boolean record)
     {
         mSourceID = ++UNIQUE_ID;
         mAudioMetadata = new AudioMetadata(mSourceID, record);
 
-        mAudioDecimationFilter = new PolyphaseFIRDecimatingFilter_RB(mDecimationCoefficients, 6);
+        mAudioDecimationFilter = new PolyphaseFIRDecimatingFilter_RB(mDecimationCoefficients, 6, 2.0f);
         mAudioDecimationFilter.setListener(new Listener<RealBuffer>()
         {
             @Override

src/dsp/filter/design/FilterViewer.java

@@ -40,37 +40,35 @@ public class FilterViewer extends Application
 	 */
 	private float[] getFilter()
 	{
-		FIRFilterSpecification specification = FIRFilterSpecification.lowPassBuilder()
-		        .sampleRate( 48000 )
-		        .gridDensity( 16 )
-                .passBandCutoff( 3000 )
+//		FIRFilterSpecification specification = FIRFilterSpecification.lowPassBuilder()
+//		        .sampleRate( 48000 )
+//		        .gridDensity( 16 )
+//                .passBandCutoff( 3000 )
+//		        .passBandAmplitude( 1.0 )
+//		        .passBandRipple( 0.01 )
+//		        .stopBandStart( 4000 )
+//		        .stopBandAmplitude( 0.0 )
+//		        .stopBandRipple( 0.027 )
+//		        .build();
+		
+		FIRFilterSpecification specification = FIRFilterSpecification.highPassBuilder()
+		        .sampleRate( 8000 )
+		        .stopBandCutoff( 250 )
+		        .stopBandAmplitude( 0.0 )
+		        .stopBandRipple( 0.01 )
+		        .passBandStart( 300 )
 		        .passBandAmplitude( 1.0 )
 		        .passBandRipple( 0.01 )
-		        .stopBandStart( 4000 )
-		        .stopBandAmplitude( 0.0 )
-		        .stopBandRipple( 0.027 )
 		        .build();
-		
-//		FIRFilterSpecification specification = FIRFilterSpecification.highPassBuilder()
-//		        .sampleRate( 8000 )
-//		        .gridDensity( 16 )
-//		        .stopBandCutoff( 2000 )
-//		        .stopBandAmplitude( 0.0 )
-//		        .stopBandRipple( 0.003 )
-//		        .passBandStart( 3000 )
-//		        .passBandAmplitude( 1.0 )
-//		        .passBandRipple( 0.001 )
-//		        .build();
 
 //		FIRFilterSpecification specification = FIRFilterSpecification.bandPassBuilder()
-//	        .sampleRate( 8000 )
-//	        .order( 164 )
-//	        .stopFrequency1( 1100 )
-//	        .passFrequencyBegin( 1200 )
-//	        .passFrequencyEnd( 2400 )
-//	        .stopFrequency2( 2500 )
-//	        .stopRipple( 0.01 )
-//	        .passRipple( 0.01 )
+//	        .sampleRate( 48000 )
+//	        .stopFrequency1( 150 )
+//	        .passFrequencyBegin( 200 )
+//	        .passFrequencyEnd( 3950 )
+//	        .stopFrequency2( 4000 )
+//	        .stopRipple( 0.0005 )
+//	        .passRipple( 0.003)
 //	        .build();
 
 		float[] taps = null;

src/dsp/filter/polyphase/PolyphaseFIRDecimatingFilter_RB.java

@@ -43,6 +43,7 @@ public class PolyphaseFIRDecimatingFilter_RB extends FIRFilter implements Listen
     private RealToRealBufferAssembler mAssembler;
     private int mDecimationRatio;
     private float mAccumulator = 0.0f;
+    private float mGain = 1.0f;
 
     /**
      * Polyphase filter stage for decimating real-valued sample buffers by the decimation ratio.  Creates a number of
@@ -55,10 +56,13 @@ public class PolyphaseFIRDecimatingFilter_RB extends FIRFilter implements Listen
      * to the nyquist frequency for an output sample rate equal to the input sample rate divided by the decimation ratio.
      *
      * @param decimationRatio to decimate the input sample rate by.
+     * @param gain to apply to the filtered output.  Use a value of 1.0 to apply no gain.
      */
-    public PolyphaseFIRDecimatingFilter_RB(float[] coefficients, int decimationRatio)
+    public PolyphaseFIRDecimatingFilter_RB(float[] coefficients, int decimationRatio, float gain)
     {
         mDecimationRatio = decimationRatio;
+        mGain = gain;
+
         createFilterStages(coefficients, mDecimationRatio);
         mFilterStagePointer = mFilterStages.size() - 1;
     }
@@ -127,7 +131,7 @@ public class PolyphaseFIRDecimatingFilter_RB extends FIRFilter implements Listen
 
         if(mFilterStagePointer < 0)
         {
-            mAssembler.receive(mAccumulator);
+            mAssembler.receive(mAccumulator * mGain);
             mAccumulator = 0.0f;
 
             mFilterStagePointer = mFilterStages.size() - 1;
@@ -177,7 +181,7 @@ public class PolyphaseFIRDecimatingFilter_RB extends FIRFilter implements Listen
             }
 
             float[] coefficients = designer.getImpulseResponse();
-            PolyphaseFIRDecimatingFilter_RB filter = new PolyphaseFIRDecimatingFilter_RB(coefficients, 6);
+            PolyphaseFIRDecimatingFilter_RB filter = new PolyphaseFIRDecimatingFilter_RB(coefficients, 6, 1.0f);
             filter.setListener(new Listener<RealBuffer>()
             {
                 @Override

src/module/decode/p25/audio/P25AudioModule.java

@@ -152,8 +152,12 @@ public class P25AudioModule extends Module implements Listener<Message>,
 
                     if (!mLibraryLoadStatusLogged)
                     {
-                        mLog.info("JMBE audio conversion library successfully loaded"
-                                + " - P25 audio will be available");
+                        StringBuilder sb = new StringBuilder();
+                        sb.append("JMBE audio conversion library [");
+                        sb.append(library.getVersion());
+                        sb.append("] successfully loaded - P25 audio will be available");
+
+                        mLog.info(sb.toString());
 
                         mLibraryLoadStatusLogged = true;
                     }