mirror of
https://github.com/DSheirer/sdrtrunk.git
synced 2026-11-13 09:07:27 -05:00
[WIP] new AFSK1200 decoder.
This commit is contained in:
Denny
320
src/main/java/io/github/dsheirer/dsp/fsk/AFSK1200Decoder.java
Normal file
320
src/main/java/io/github/dsheirer/dsp/fsk/AFSK1200Decoder.java
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@@ -0,0 +1,320 @@
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/*******************************************************************************
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* sdr-trunk
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* Copyright (C) 2014-2018 Dennis Sheirer
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*
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* This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
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||||
* 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/>
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*
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******************************************************************************/
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package io.github.dsheirer.dsp.fsk;
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import io.github.dsheirer.bits.MessageFramer;
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import io.github.dsheirer.buffer.BooleanAveragingBuffer;
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import io.github.dsheirer.buffer.FloatAveragingBuffer;
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import io.github.dsheirer.dsp.filter.design.FilterDesignException;
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import io.github.dsheirer.dsp.filter.fir.FIRFilterSpecification;
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import io.github.dsheirer.dsp.filter.fir.real.RealFIRFilter2;
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import io.github.dsheirer.dsp.filter.fir.remez.RemezFIRFilterDesigner;
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import io.github.dsheirer.dsp.filter.resample.RealResampler;
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import io.github.dsheirer.dsp.mixer.IOscillator;
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import io.github.dsheirer.dsp.mixer.Oscillator;
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import io.github.dsheirer.dsp.symbol.ISyncDetectListener;
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import io.github.dsheirer.sample.Listener;
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import io.github.dsheirer.sample.buffer.ReusableBuffer;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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/**
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* Binary Frequency Shift Keying (2FSK) correlation decoder. Provides normal or inverted decoded output.
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*/
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public class AFSK1200Decoder implements Listener<ReusableBuffer>, ISyncDetectListener, ISyncStateListener
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{
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private final static Logger mLog = LoggerFactory.getLogger(AFSK1200Decoder.class);
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public enum Output
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{
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NORMAL, INVERTED
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}
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public static final double TARGET_SAMPLE_RATE = 7200.0d;
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public static final int SAMPLES_PER_SYMBOL = 6; //TARGET_SAMPLE_RATE / 1200;
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public static final float COARSE_TIMING_GAIN = 1.0f / 3.0f;
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protected static final float MEDIUM_TIMING_GAIN = 1.0f / 4.0f;
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protected static final float FINE_TIMING_GAIN = 1.0f / 5.0f;
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private static float[] sBandPassFilterCoefficients;
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static
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{
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FIRFilterSpecification specification = FIRFilterSpecification.bandPassBuilder()
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.sampleRate(8000)
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.stopFrequency1(1000)
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.passFrequencyBegin(1100)
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.passFrequencyEnd(1900)
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.stopFrequency2(2000)
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.stopRipple(0.000001)
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.passRipple(0.00001)
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.build();
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try
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{
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RemezFIRFilterDesigner designer = new RemezFIRFilterDesigner(specification);
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if(designer.isValid())
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{
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sBandPassFilterCoefficients = designer.getImpulseResponse();
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}
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}
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catch(FilterDesignException fde)
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{
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mLog.error("Filter design error", fde);
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}
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}
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private Correlator mCorrelator1200 = new Correlator(TARGET_SAMPLE_RATE, 1200.0, SAMPLES_PER_SYMBOL);
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private Correlator mCorrelator1800 = new Correlator(TARGET_SAMPLE_RATE, 1800.0, SAMPLES_PER_SYMBOL);
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private float[] mCorrelationValues1200;
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private float[] mCorrelationValues1800;
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protected boolean mNormalOutput;
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protected float mSymbolTimingGain = COARSE_TIMING_GAIN;
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protected SampleBuffer mSampleBuffer;
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protected ZeroCrossingErrorDetector mTimingErrorDetector = new ZeroCrossingErrorDetector(SAMPLES_PER_SYMBOL);
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protected SynchronizationMonitor mSynchronizationMonitor;
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private RealFIRFilter2 mBandPassFilter = new RealFIRFilter2(sBandPassFilterCoefficients);
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protected MessageFramer mMessageFramer;
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private boolean mSampleDecision;
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//Resample to an integral of the baud rate 1200 baud * 6 samples per symbol = 7200.0 Hertz
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private RealResampler mResampler = new RealResampler(8000.0, TARGET_SAMPLE_RATE, 2000, 1);
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public AFSK1200Decoder(int messageLength, SampleBuffer sampleBuffer, ZeroCrossingErrorDetector detector, boolean invertOutput)
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{
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mSynchronizationMonitor = new SynchronizationMonitor(messageLength);
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mSynchronizationMonitor.setListener(this);
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mTimingErrorDetector = detector;
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mSampleBuffer = sampleBuffer;
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mSampleBuffer.setTimingGain(mSymbolTimingGain);
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mResampler.setListener(new Decoder(SAMPLES_PER_SYMBOL));
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mNormalOutput = !invertOutput;
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}
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public AFSK1200Decoder(int messageLength, boolean invertOutput)
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{
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this(messageLength, new SampleBuffer(SAMPLES_PER_SYMBOL, COARSE_TIMING_GAIN),
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new ZeroCrossingErrorDetector(SAMPLES_PER_SYMBOL), invertOutput);
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}
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/**
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* Disposes of all references to prepare for garbage collection
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*/
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public void dispose()
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{
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}
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/**
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* Implements the ISyncDetectedListener interface to be notified of message sync detection events.
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*
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* This allows the internal timing error detector to adjust symbol timing error gain levels according to the
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* message synchronization state to quickly adjust to initial signal streams or to reduce gain levels once
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* synchronization has been achieved.
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*/
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@Override
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public void syncDetected()
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{
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mSynchronizationMonitor.syncDetected();
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}
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/**
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* Processes the buffer samples by converting all samples to boolean values reflecting if the sample value is
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* greater than zero (or not). Average symbol timing offset is calculated for the full buffer and the offset is
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* adjusted and then each of the symbols are decoded using a simple majority decision.
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*
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* @param buffer containing 8.0 kHz unfiltered FM demodulated audio samples with sub-audible LTR signalling.
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*/
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@Override
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public void receive(ReusableBuffer buffer)
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{
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// ReusableBuffer bandPassFiltered = mBandPassFilter.filter(buffer);
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// mResampler.resample(bandPassFiltered);
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mResampler.resample(buffer);
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}
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protected void dispatch(boolean symbol)
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{
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if(mMessageFramer != null)
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{
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mMessageFramer.receive(mNormalOutput ? symbol : !symbol);
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}
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}
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/**
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* Registers a listener to receive decoded LTR symbols.
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*
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* @param messageFramer to receive symbols.
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*/
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public void setMessageFramer(MessageFramer messageFramer)
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{
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mMessageFramer = messageFramer;
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}
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/**
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* Removes the symbol listener from receiving decoded LTR symbols.
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*/
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public void removeListener()
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{
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mMessageFramer = null;
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}
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/**
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* Implements the ISyncStateListener interface to receive synchronization state events and adjust the symbol timing
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* error gain levels on the internal timing error detector.
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*
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* Gain levels are defined relative to a unit gain of 1.0 over a number of symbol periods. LTR uses an initial
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* ramp-up symbol reversal pattern of 0101 which provides three zero crossing detection opportunities for the timing
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* error detector, therefore we react to a COARSE gain state to average timing error over 3 symbols.
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*
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* @param syncState from an external synchronization state monitor
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*/
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@Override
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public void setSyncState(SyncState syncState)
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{
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switch(syncState)
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{
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case FINE:
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mSymbolTimingGain = FINE_TIMING_GAIN;
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break;
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case MEDIUM:
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mSymbolTimingGain = MEDIUM_TIMING_GAIN;
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break;
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case COARSE:
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mSymbolTimingGain = COARSE_TIMING_GAIN;
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break;
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default:
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throw new IllegalArgumentException("Unrecognized sync state level: " + syncState.name());
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}
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mSampleBuffer.setTimingGain(mSymbolTimingGain);
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}
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public class Decoder implements Listener<ReusableBuffer>
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{
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private BooleanAveragingBuffer mSampleAveragingBuffer;
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private Decoder(int samplesPerSymbol)
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{
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mSampleAveragingBuffer = new BooleanAveragingBuffer(samplesPerSymbol);
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}
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@Override
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public void receive(ReusableBuffer buffer)
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{
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//Calculate correlation values against each 1200/1800 reference signal
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mCorrelationValues1200 = mCorrelator1200.process(buffer);
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mCorrelationValues1800 = mCorrelator1800.process(buffer);
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buffer.decrementUserCount();
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for(int x = 0; x < mCorrelationValues1200.length; x++)
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{
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//1200 = Mark (1) and 1800 = Space (0)
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mSampleDecision = mCorrelationValues1200[x] > mCorrelationValues1800[x];
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// mSampleDecision = mSampleAveragingBuffer.getAverage(mSampleDecision);
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mSampleBuffer.receive(mSampleDecision);
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mTimingErrorDetector.receive(mSampleDecision);
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if(mSampleBuffer.hasSymbol())
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{
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dispatch(mSampleBuffer.getSymbol());
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// mSampleBuffer.resetAndAdjust(-mTimingErrorDetector.getError());
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mSampleBuffer.resetAndAdjust(0.0f);
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mSynchronizationMonitor.increment();
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}
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}
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}
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}
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/**
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* Generates a correlation value for each FM demodulated signal against an established reference frequency,
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* correlated and averaged over separate periods relative to the samples per symbol period.
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*/
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public class Correlator
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{
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private FloatAveragingBuffer mAveragingBuffer;
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private float[] mReferenceSamples;
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private float[] mDemodulatedSamples;
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private float[] mCorrelationValues;
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private float mCorrelationAccumulator;
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/**
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* Constructs a correlator instance for the specified parameters
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* @param sampleRate of the incoming sample stream. Note: this should be an integral of the symbol rate.
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* @param frequency of the mark or space symbol to test for correlation
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* @param samplesPerSymbol to determine the correlation and averaging periods
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*/
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public Correlator(double sampleRate, double frequency, int samplesPerSymbol)
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{
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//Adjust correlation period and averaging period to provide optimal correlation for a given samples/symbol.
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//These values are optimized for 6 samples per symbol with averaging over 7 samples and correlation over an
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//8 sample period.
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int correlationPeriod = samplesPerSymbol + 2;
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mAveragingBuffer = new FloatAveragingBuffer(samplesPerSymbol + 1);
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mDemodulatedSamples = new float[correlationPeriod];
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IOscillator referenceGenerator = new Oscillator(frequency, sampleRate);
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mReferenceSamples = referenceGenerator.generateReal(correlationPeriod);
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}
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/**
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* Processes each sample in the incoming sample buffer against a generated reference sample set for one symbol
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* period to derive a correlation value that is in-turn averaged over one symbol period.
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*
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* @param reusableBuffer containing FM demodulated samples
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* @return a reusable array of correlation values for each sample
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*/
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public float[] process(ReusableBuffer reusableBuffer)
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{
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if(mCorrelationValues == null || mCorrelationValues.length != reusableBuffer.getSampleCount())
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{
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mCorrelationValues = new float[reusableBuffer.getSampleCount()];
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}
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float[] samples = reusableBuffer.getSamples();
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int y;
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for(int x = 0; x < samples.length; x++)
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{
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//Note: we're using array copy and dot product structures that the JRE can promote to SIMD intrinsics
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//when the host processor provides SIMD capabilities
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System.arraycopy(mDemodulatedSamples, 1, mDemodulatedSamples, 0, mDemodulatedSamples.length - 1);
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mDemodulatedSamples[mDemodulatedSamples.length - 1] = samples[x];
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mCorrelationAccumulator = 0.0f;
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for(y = 0; y < mDemodulatedSamples.length; y++)
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{
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mCorrelationAccumulator += mDemodulatedSamples[y] * mReferenceSamples[y];
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}
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//Add the absolute value of correlation accumulator value to the averaging buffer and store the current
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// average as the correlation value for this sample
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mCorrelationValues[x] = mAveragingBuffer.get(Math.abs(mCorrelationAccumulator));
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}
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return mCorrelationValues;
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}
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}
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}
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@@ -0,0 +1,55 @@
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/*******************************************************************************
|
||||
* sdr-trunk
|
||||
* Copyright (C) 2014-2018 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/>
|
||||
*
|
||||
******************************************************************************/
|
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package io.github.dsheirer.dsp.fsk;
|
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import io.github.dsheirer.sample.Broadcaster;
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import io.github.dsheirer.sample.Listener;
|
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public class AFSK1200DecoderInstrumented extends AFSK1200Decoder
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{
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private Broadcaster<Boolean> mSymbolBroadcaster = new Broadcaster<>();
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public AFSK1200DecoderInstrumented(int messageLength, SampleBuffer sampleBuffer, ZeroCrossingErrorDetector detector, boolean invertOutput)
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{
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super(messageLength, new SampleBufferInstrumented(SAMPLES_PER_SYMBOL, COARSE_TIMING_GAIN),
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new ZeroCrossingErrorDetectorInstrumented(SAMPLES_PER_SYMBOL), invertOutput);
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}
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public SampleBufferInstrumented getSampleBuffer()
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{
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return (SampleBufferInstrumented)mSampleBuffer;
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}
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public ZeroCrossingErrorDetectorInstrumented getErrorDetector()
|
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{
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return (ZeroCrossingErrorDetectorInstrumented)mTimingErrorDetector;
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}
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protected void dispatch(boolean symbol)
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{
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if(mMessageFramer != null)
|
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{
|
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mMessageFramer.receive(mNormalOutput ? symbol : !symbol);
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}
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mSymbolBroadcaster.broadcast(symbol);
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}
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|
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public void addListener(Listener<Boolean> listener)
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{
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mSymbolBroadcaster.addListener(listener);
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}
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}
|
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122
src/main/java/io/github/dsheirer/dsp/fsk/AFSKTest.java
Normal file
122
src/main/java/io/github/dsheirer/dsp/fsk/AFSKTest.java
Normal file
@@ -0,0 +1,122 @@
|
||||
/*******************************************************************************
|
||||
* sdr-trunk
|
||||
* Copyright (C) 2014-2018 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 io.github.dsheirer.dsp.fsk;
|
||||
|
||||
import io.github.dsheirer.buffer.FloatAveragingBuffer;
|
||||
import io.github.dsheirer.dsp.mixer.IOscillator;
|
||||
import io.github.dsheirer.dsp.mixer.Oscillator;
|
||||
import io.github.dsheirer.sample.complex.Complex;
|
||||
import org.slf4j.Logger;
|
||||
import org.slf4j.LoggerFactory;
|
||||
|
||||
import java.text.DecimalFormat;
|
||||
|
||||
public class AFSKTest
|
||||
{
|
||||
private final static Logger mLog = LoggerFactory.getLogger(AFSK1200Decoder.class);
|
||||
|
||||
private static final DecimalFormat df = new DecimalFormat("00.000");
|
||||
|
||||
public static String format(double value)
|
||||
{
|
||||
if(value > 0)
|
||||
{
|
||||
return " " + df.format(value);
|
||||
}
|
||||
else
|
||||
{
|
||||
return df.format(value);
|
||||
}
|
||||
}
|
||||
|
||||
public static float[] generateAFSK1200(boolean[] symbols, int samplesPerSymbol, float gain)
|
||||
{
|
||||
float[] samples = new float[symbols.length * samplesPerSymbol];
|
||||
|
||||
Oscillator oscillator = new Oscillator(1200.0, (double)samplesPerSymbol * 1200);
|
||||
|
||||
for(int x = 0; x < symbols.length; x++)
|
||||
{
|
||||
oscillator.setFrequency(symbols[x] ? 1200.0 : 1800.0);
|
||||
|
||||
for(int y = 0; y < samplesPerSymbol; y++)
|
||||
{
|
||||
Complex sample = new Complex(oscillator.inphase(), oscillator.quadrature());
|
||||
sample.multiply(gain);
|
||||
samples[x * samplesPerSymbol + y] = sample.inphase();
|
||||
oscillator.rotate();
|
||||
}
|
||||
}
|
||||
|
||||
return samples;
|
||||
}
|
||||
|
||||
public static void main(String[] args)
|
||||
{
|
||||
int sampleSize = 6;
|
||||
|
||||
FloatAveragingBuffer avg1200 = new FloatAveragingBuffer(sampleSize);
|
||||
FloatAveragingBuffer avg1800 = new FloatAveragingBuffer(sampleSize);
|
||||
|
||||
IOscillator oscillator1200 = new Oscillator(1200.0, 7200.0);
|
||||
IOscillator oscillator1800 = new Oscillator(1800.0, 7200.0);
|
||||
oscillator1200.generateReal(1);
|
||||
oscillator1800.generateReal(1);
|
||||
|
||||
float[] reference1200 = oscillator1200.generateReal(sampleSize);
|
||||
float[] reference1800 = oscillator1800.generateReal(sampleSize);
|
||||
|
||||
boolean[] symbols = new boolean[]{true,false,true,false,true,false,true,false,true,true,true,false,true,false,
|
||||
false,false,true,false,false,false,false,true,false,true,true,true,true,false,true,true,false,true,false,
|
||||
true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,
|
||||
false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,
|
||||
true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,
|
||||
false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,
|
||||
true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,
|
||||
false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,true,false,
|
||||
true,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,
|
||||
false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false,false};
|
||||
|
||||
float[] samples = generateAFSK1200(symbols, 6, 0.5f);
|
||||
|
||||
mLog.debug("Length:" + samples.length);
|
||||
|
||||
int offset = 0;
|
||||
|
||||
float correlation1200 = 0.0f;
|
||||
float correlation1800 = 0.0f;
|
||||
|
||||
while(offset + sampleSize < samples.length)
|
||||
{
|
||||
correlation1200 = 0.0f;
|
||||
correlation1800 = 0.0f;
|
||||
|
||||
for(int x = 0; x < sampleSize; x++)
|
||||
{
|
||||
correlation1200 += reference1200[x] * samples[x + offset];
|
||||
correlation1800 += reference1800[x] * samples[x + offset];
|
||||
}
|
||||
|
||||
correlation1200 = avg1200.get(Math.abs(correlation1200));
|
||||
correlation1800 = avg1800.get(Math.abs(correlation1800));
|
||||
|
||||
mLog.debug(offset + " 1200:" + format(correlation1200) + " 1800:" + format(correlation1800) +
|
||||
" Decision: " + (correlation1200 > correlation1800 ? "0" : "1"));
|
||||
|
||||
offset++;
|
||||
}
|
||||
}
|
||||
}
|
||||
@@ -46,7 +46,8 @@ public class ZeroCrossingErrorDetector
|
||||
public ZeroCrossingErrorDetector(float samplesPerSymbol)
|
||||
{
|
||||
mBuffer = new boolean[(int)Math.ceil(samplesPerSymbol)];
|
||||
mZeroCrossingIdeal = mBuffer.length - 1.5f - (samplesPerSymbol / 2.0f);
|
||||
// mZeroCrossingIdeal = mBuffer.length - 1.5f - (samplesPerSymbol / 2.0f); //Preserve this for LTR
|
||||
mZeroCrossingIdeal = (samplesPerSymbol / 2.0f);
|
||||
}
|
||||
|
||||
/**
|
||||
|
||||
Reference in New Issue
Block a user