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[WIP] Updates the LTR-Standard and LTR-Net decoders to use a new LTR

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decoder with a zero-crossing symbol timing error detector.  The new
decoder is optimized for 8 kHz FM demodulated audio produced by the
AudioModule.
This commit is contained in:
Denny
2018-06-02 08:47:48 -04:00
parent c13315f731
commit a898be265f
64 changed files with 2660 additions and 1285 deletions
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150
src/main/java/io/github/dsheirer/module/demodulate/fm/FMDemodulatorModule.java
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@@ -19,50 +19,55 @@ import io.github.dsheirer.dsp.filter.FilterFactory;
import io.github.dsheirer.dsp.filter.Window;
import io.github.dsheirer.dsp.filter.design.FilterDesignException;
import io.github.dsheirer.dsp.filter.fir.FIRFilterSpecification;
import io.github.dsheirer.dsp.filter.fir.complex.ComplexFIRFilter_CB_CB;
import io.github.dsheirer.dsp.fm.FMDemodulator_CB;
import io.github.dsheirer.dsp.filter.fir.complex.ComplexFIRFilter2;
import io.github.dsheirer.dsp.filter.resample.RealResampler;
import io.github.dsheirer.dsp.fm.FMDemodulator;
import io.github.dsheirer.module.Module;
import io.github.dsheirer.sample.Listener;
import io.github.dsheirer.sample.buffer.IReusableBufferProvider;
import io.github.dsheirer.sample.buffer.IReusableComplexBufferListener;
import io.github.dsheirer.sample.buffer.ReusableBuffer;
import io.github.dsheirer.sample.buffer.ReusableComplexBuffer;
import io.github.dsheirer.sample.real.IUnFilteredRealBufferProvider;
import io.github.dsheirer.sample.real.RealBuffer;
import io.github.dsheirer.source.ISourceEventListener;
import io.github.dsheirer.source.SourceEvent;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* FM Demodulator with integrated fractional resampler.
*
* Note: no filtering is applied to the demodulated audio.
*/
public class FMDemodulatorModule extends Module implements ISourceEventListener, IReusableComplexBufferListener,
IUnFilteredRealBufferProvider
Listener<ReusableComplexBuffer>, IReusableBufferProvider
{
private final static Logger mLog = LoggerFactory.getLogger(FMDemodulatorModule.class);
private ComplexFIRFilter_CB_CB mIQFilter;
private FMDemodulator_CB mDemodulator;
private ReusableBufferProcessor mReusableBufferProcessor = new ReusableBufferProcessor();
private ComplexFIRFilter2 mIQFilter;
private FMDemodulator mDemodulator = new FMDemodulator();
private RealResampler mResampler;
private SourceEventProcessor mSourceEventProcessor = new SourceEventProcessor();
private int mPassFrequency;
private int mStopFrequency;
private Listener<ReusableBuffer> mResampledReusableBufferListener;
private double mChannelBandwidth;
private double mOutputSampleRate;
/**
* FM Demodulator with I/Q filter. Demodulated output is unfiltered and may contain a DC component.
* Creates an FM demodulator for the specified channel bandwidth and output sample rate.
*
* @param pass - pass frequency for IQ filtering prior to demodulation. This
* frequency should be less than or equal to half of the signal bandwidth since the filter will
* be applied against each of the inphase and quadrature signals and the
* combined pass bandwidth will be twice this value.
* A baseband I/Q filter will be constructed to low pass filter the incoming sample buffer stream to the desired
* channel bandwidth and the demodulated output will be resampled to the desired output sample rate. The input
* low pass filter is constructed at runtime based on receiving a sample rate notification source event.
*/
public FMDemodulatorModule(int pass, int stop)
public FMDemodulatorModule(double channelBandwidth, double outputSampleRate)
{
mDemodulator = new FMDemodulator_CB(1.0f);
mPassFrequency = pass;
mStopFrequency = stop;
mChannelBandwidth = channelBandwidth;
mOutputSampleRate = outputSampleRate;
}
@Override
public Listener<ReusableComplexBuffer> getReusableComplexBufferListener()
{
return mReusableBufferProcessor;
return this;
}
@Override
@@ -90,18 +95,6 @@ public class FMDemodulatorModule extends Module implements ISourceEventListener,
mDemodulator.reset();
}
@Override
public void setUnFilteredRealBufferListener(Listener<RealBuffer> listener)
{
mDemodulator.setListener(listener);
}
@Override
public void removeUnFilteredRealBufferListener()
{
mDemodulator.removeListener();
}
@Override
public void start()
{
@@ -112,27 +105,38 @@ public class FMDemodulatorModule extends Module implements ISourceEventListener,
{
}
/**
* Receives complex buffers and sends them through the filtering and demodulation process. Manages accounting for
* the reusable buffers.
*/
public class ReusableBufferProcessor implements Listener<ReusableComplexBuffer>
@Override
public void setBufferListener(Listener<ReusableBuffer> listener)
{
@Override
public void receive(ReusableComplexBuffer reusableComplexBuffer)
mResampledReusableBufferListener = listener;
}
@Override
public void removeBufferListener()
{
mResampledReusableBufferListener = null;
}
@Override
public void receive(ReusableComplexBuffer reusableComplexBuffer)
{
if(mIQFilter == null)
{
if(mIQFilter == null)
{
reusableComplexBuffer.decrementUserCount();
throw new IllegalStateException("FM demodulator module must receive a sample rate change source " +
"event before it can process complex sample buffers");
}
float[] samples = reusableComplexBuffer.getSamplesCopy();
mIQFilter.receive(samples);
reusableComplexBuffer.decrementUserCount();
throw new IllegalStateException("FM demodulator module must receive a sample rate change source " +
"event before it can process complex sample buffers");
}
ReusableComplexBuffer basebandFilteredBuffer = mIQFilter.filter(reusableComplexBuffer);
ReusableBuffer demodulatedBuffer = mDemodulator.demodulate(basebandFilteredBuffer);
if(mResampler != null)
{
mResampler.resample(demodulatedBuffer);
}
else
{
demodulatedBuffer.decrementUserCount();
}
}
@@ -146,18 +150,35 @@ public class FMDemodulatorModule extends Module implements ISourceEventListener,
{
if(sourceEvent.getEvent() == SourceEvent.Event.NOTIFICATION_SAMPLE_RATE_CHANGE)
{
if(mIQFilter != null)
{
mIQFilter.dispose();
mIQFilter = null;
}
double sampleRate = sourceEvent.getValue().doubleValue();
if((sampleRate < (2.0 * mChannelBandwidth)))
{
throw new IllegalStateException("FM Demodulator with channel bandwidth [" + mChannelBandwidth +
"] requires a channel sample rate of [" + (2.0 * mChannelBandwidth + "] - sample rate of [" +
sampleRate + "] is not supported"));
}
double cutoff = sampleRate / 4.0;
int passBandStop = (int)cutoff - 500;
int stopBandStart = (int)cutoff + 500;
float[] filterTaps = null;
FIRFilterSpecification specification = FIRFilterSpecification.lowPassBuilder()
.sampleRate(sampleRate)
.gridDensity(16)
.oddLength(true)
.passBandCutoff(mPassFrequency)
.passBandCutoff(passBandStop)
.passBandAmplitude(1.0)
.passBandRipple(0.01)
.stopBandStart(mStopFrequency)
.stopBandStart(stopBandStart)
.stopBandAmplitude(0.0)
.stopBandRipple(0.028) //Approximately 60 dB attenuation
.build();
@@ -169,18 +190,35 @@ public class FMDemodulatorModule extends Module implements ISourceEventListener,
catch(FilterDesignException fde)
{
mLog.error("Couldn't design FM demodulator remez filter for sample rate [" + sampleRate +
"] pass frequency [" + mPassFrequency + "] and stop frequency [" + mStopFrequency +
"] pass frequency [" + passBandStop + "] and stop frequency [" + stopBandStart +
"] - using sinc filter");
}
if(filterTaps == null)
{
filterTaps = FilterFactory.getLowPass(sampleRate, mPassFrequency, mStopFrequency, 60,
filterTaps = FilterFactory.getLowPass(sampleRate, passBandStop, stopBandStart, 60,
Window.WindowType.HAMMING, true);
}
mIQFilter = new ComplexFIRFilter_CB_CB(filterTaps, 1.0f);
mIQFilter.setListener(mDemodulator);
mIQFilter = new ComplexFIRFilter2(filterTaps);
mResampler = new RealResampler(sampleRate, mOutputSampleRate);
mResampler.setListener(new Listener<ReusableBuffer>()
{
@Override
public void receive(ReusableBuffer reusableBuffer)
{
if(mResampledReusableBufferListener != null)
{
mResampledReusableBufferListener.receive(reusableBuffer);
}
else
{
reusableBuffer.decrementUserCount();
}
}
});
}
}
}