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P25 audio work in progress - started work on exposing 88-bit (11-byte) IMBE voice frames from LDU messages. Added deinterleave, derandomize and the Golay(23,12,7) error detection and correction to LDU voice messages. Hamming edac still remains to be implemented. Plan to create a separate project to produce an imbe FormatConversionProvider that will convert 88-bit imbe frames to PCM audio that is then in a standard format for audio playback, recording, or conversion to another format like shoutcast.

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dennis.sheirer
2015-03-01 15:40:25 +00:00
parent 1f13f7eec2
commit 52f2e3bdca
9 changed files with 544 additions and 80 deletions
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119
src/dsp/psk/CQPSKDemodulator.java
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@@ -36,6 +36,10 @@ import org.slf4j.LoggerFactory;
import sample.Listener;
import sample.Provider;
import sample.complex.ComplexSample;
import source.tuner.FrequencyChangeEvent;
import source.tuner.FrequencyChangeEvent.Attribute;
import source.tuner.FrequencyChangeListener;
import buffer.FloatAveragingBuffer;
import dsp.filter.interpolator.QPSKInterpolator;
/**
@@ -51,11 +55,13 @@ public class CQPSKDemodulator implements Listener<ComplexSample>,
{
private final static Logger mLog =
LoggerFactory.getLogger( CQPSKDemodulator.class );
private Listener<ComplexSample> mListener;
private GardnerDetector mGardnerDetector = new GardnerDetector();
private FrequencyChangeListener mFrequencyChangeListener;
public CQPSKDemodulator()
{
}
@@ -82,6 +88,75 @@ public class CQPSKDemodulator implements Listener<ComplexSample>,
return value;
}
public void addListener( FrequencyChangeListener listener )
{
mFrequencyChangeListener = listener;
}
public void removeListener( FrequencyChangeListener listener )
{
mFrequencyChangeListener = null;
}
/**
* Processes the current loop frequency of the costas loop and broadcasts
* tuner frequency offset adjustments 10 times a second as needed to keep
* the frequency offset below half of the maximum frequency
*/
public class FrequencyControl
{
/* Set the trigger threshold at half of the maximum costas loop control
* frequency */
private static final float CORRECTION_THRESHOLD_FREQUENCY =
( 2.0f * (float)Math.PI * 600.0f ) / 48000.0f;
private FloatAveragingBuffer mBuffer = new FloatAveragingBuffer( 40 );
private long mFrequencyError = 0;
private int mCounter = 0;
public void receive( float frequency )
{
// mCounter++;
//
// if( mCounter >= 480 )
// {
// float average = mBuffer.get( frequency );
// mLog.debug( "Avg:" + average + " Threshold:" + CORRECTION_THRESHOLD_FREQUENCY);
//
// boolean correctionNeeded = false;
//
// if( average > CORRECTION_THRESHOLD_FREQUENCY )
// {
// mFrequencyError--;
//
// correctionNeeded = true;
// }
// else if( average < -CORRECTION_THRESHOLD_FREQUENCY )
// {
// mFrequencyError++;
//
// correctionNeeded = true;
// }
//
// if( correctionNeeded && mFrequencyChangeListener != null )
// {
// mLog.debug( "Issuing Frequency Correction: " + mFrequencyError );
// mFrequencyChangeListener.frequencyChanged(
// new FrequencyChangeEvent( Attribute.FREQUENCY_ERROR,
// mFrequencyError ) );
// }
//
// mCounter = 0;
// }
// else
// {
// mBuffer.get( frequency );
// }
}
}
/**
* Gardner symbol timing detector
@@ -209,10 +284,15 @@ public class CQPSKDemodulator implements Listener<ComplexSample>,
}
/**
* Costas Loop - phase locked loop synchronized to the incoming signal.
* Costas Loop - phase locked loop synchronized to the frequency offset of
* the incoming signal to enable the signal to be mixed down to zero offset
* for proper synchronization. The mFrequency value indicates the detected
* frequency offset. We attempt to keep that value close to zero by issuing
* frequency adjustments to the tuner channel source.
*
* Ported from gnuradio/control_loop and gnuradio/mpsk_receiver_cc
* using initialization values from KA1RBI's OP25/cqpsk.py
* Most of the costas loop code was ported from gnuradio/control_loop and
* gnuradio/mpsk_receiver_cc using initialization values from KA1RBI's
* OP25/cqpsk.py
*/
public class CostasLoop implements Listener<ComplexSample>
{
@@ -221,6 +301,9 @@ public class CQPSKDemodulator implements Listener<ComplexSample>,
/* 45 degree rotation angle */
public static final float THETA = (float)( Math.PI / 4.0d );
private static final float MAXIMUM_FREQUENCY = ( 2.0f * (float)Math.PI *
1200.0f ) / 48000.0f;
/* http://www.trondeau.com/blog/2011/8/13/control-loop-gain-values.html */
private float mDamping = (float)Math.sqrt( 2.0 ) / 2.0f;
@@ -238,9 +321,8 @@ public class CQPSKDemodulator implements Listener<ComplexSample>,
private float mLoopPhase = 0.0f;
private float mLoopFrequency = 0.0f;
private float mMaximumFrequency = ( 2.0f * (float)Math.PI * 1200.0f ) /
48000.0f;
private FrequencyControl mFrequencyControl = new FrequencyControl();
public CostasLoop()
{
@@ -289,12 +371,6 @@ public class CQPSKDemodulator implements Listener<ComplexSample>,
/* Adjust for phase error */
adjust( phaseError );
/* Maintain phase between +/- 2 * PI */
unwrapPhase();
/* Limit frequency to +/- maximum frequency */
limitFrequency();
}
/**
@@ -307,18 +383,27 @@ public class CQPSKDemodulator implements Listener<ComplexSample>,
{
mLoopFrequency += mBetaGain * phase_error;
mLoopPhase += mLoopFrequency + mAlphaGain * phase_error;
/* Maintain phase between +/- 2 * PI */
unwrapPhase();
/* Limit frequency to +/- maximum frequency */
limitFrequency();
}
private void limitFrequency()
{
if( mLoopFrequency > mMaximumFrequency )
/* Check for and issue tuner offset correction */
mFrequencyControl.receive( mLoopFrequency );
if( mLoopFrequency > MAXIMUM_FREQUENCY )
{
mLoopFrequency = mMaximumFrequency;
mLoopFrequency = MAXIMUM_FREQUENCY;
}
if( mLoopFrequency < -mMaximumFrequency )
if( mLoopFrequency < -MAXIMUM_FREQUENCY )
{
mLoopFrequency = -mMaximumFrequency;
mLoopFrequency = -MAXIMUM_FREQUENCY;
}
}