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added Demodulator class

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This commit is contained in:
Ahmet Inan 2024-04-16 11:43:43 +02:00
parent fee4012c6a
commit b8c98317b1
2 changed files with 88 additions and 66 deletions
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73
app/src/main/java/xdsopl/robot36/Demodulator.java Normal file
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@ -0,0 +1,73 @@
/*
SSTV Demodulator
Copyright 2024 Ahmet Inan <xdsopl@gmail.com>
*/
package xdsopl.robot36;
public class Demodulator {
private final SimpleMovingAverage powerAvg;
private final ComplexMovingAverage syncPulseFilter;
private final ComplexMovingAverage scanLineFilter;
private final ComplexMovingAverage baseBandLowPass;
private final FrequencyModulation scanLineDemod;
private final Phasor syncPulseOscillator;
private final Phasor scanLineOscillator;
private final Phasor baseBandOscillator;
private final Delay syncPulseDelay;
private final Delay scanLineDelay;
private Complex baseBand;
private Complex syncPulse;
private Complex scanLine;
Demodulator(int sampleRate) {
double powerWindowSeconds = 0.5;
int powerWindowSamples = (int) Math.round(powerWindowSeconds * sampleRate) | 1;
powerAvg = new SimpleMovingAverage(powerWindowSamples);
float blackFrequency = 1500;
float whiteFrequency = 2300;
float scanLineBandwidth = whiteFrequency - blackFrequency;
scanLineDemod = new FrequencyModulation(scanLineBandwidth, sampleRate);
float scanLineCutoff = scanLineBandwidth / 2;
int scanLineFilterSamples = (int) Math.round(0.443 * sampleRate / scanLineCutoff) | 1;
scanLineFilter = new ComplexMovingAverage(scanLineFilterSamples);
double syncPulseSeconds = 0.009;
int syncPulseFilterSamples = (int) Math.round(syncPulseSeconds * sampleRate) | 1;
syncPulseFilter = new ComplexMovingAverage(syncPulseFilterSamples);
float lowestFrequency = 1100;
float highestFrequency = 2300;
float cutoffFrequency = (highestFrequency - lowestFrequency) / 2;
int lowPassSamples = (int) Math.round(0.443 * sampleRate / cutoffFrequency) | 1;
baseBandLowPass = new ComplexMovingAverage(lowPassSamples);
float centerFrequency = (lowestFrequency + highestFrequency) / 2;
baseBandOscillator = new Phasor(-centerFrequency, sampleRate);
float syncPulseFrequency = 1200;
syncPulseOscillator = new Phasor(-(syncPulseFrequency - centerFrequency), sampleRate);
float grayFrequency = (blackFrequency + whiteFrequency) / 2;
scanLineOscillator = new Phasor(-(grayFrequency - centerFrequency), sampleRate);
int syncPulseDelaySamples = (powerWindowSamples - 1) / 2;
syncPulseDelay = new Delay(syncPulseDelaySamples);
int scanLineDelaySamples = (powerWindowSamples - 1) / 2 + (syncPulseFilterSamples - 1) / 2 - (scanLineFilterSamples - 1) / 2;
scanLineDelay = new Delay(scanLineDelaySamples);
baseBand = new Complex();
syncPulse = new Complex();
scanLine = new Complex();
}
public void process(float[] buffer) {
for (int i = 0; i < buffer.length; ++i) {
baseBand = baseBandLowPass.avg(baseBand.set(buffer[i]).mul(baseBandOscillator.rotate()));
syncPulse = syncPulseFilter.avg(syncPulse.set(baseBand).mul(syncPulseOscillator.rotate()));
scanLine = scanLineFilter.avg(scanLine.set(baseBand).mul(scanLineOscillator.rotate()));
float syncPulseValue = syncPulseDelay.push(syncPulse.norm()) / powerAvg.avg(baseBand.norm());
float scanLineValue = scanLineDelay.push(scanLineDemod.demod(scanLine));
float syncPulseLevel = Math.min(Math.max(syncPulseValue, 0), 1);
float scanLineLevel = Math.min(Math.max(0.5f * (scanLineValue + 1), 0), 1);
if (syncPulseLevel > 0.1)
buffer[i] = -syncPulseLevel;
else
buffer[i] = scanLineLevel;
}
}
}

81
app/src/main/java/xdsopl/robot36/MainActivity.java
View file

@ -37,19 +37,8 @@ public class MainActivity extends AppCompatActivity {
private float[] recordBuffer; private float[] recordBuffer;
private AudioRecord audioRecord; private AudioRecord audioRecord;
private TextView status; private TextView status;
private Delay syncPulseDelay; private Demodulator demodulator;
private Delay scanLineDelay;
private SimpleMovingAverage powerAvg;
private ComplexMovingAverage syncPulseFilter;
private ComplexMovingAverage scanLineFilter;
private ComplexMovingAverage baseBandLowPass;
private FrequencyModulation scanLineDemod;
private Phasor syncPulseOscillator;
private Phasor scanLineOscillator;
private Phasor baseBandOscillator;
private Complex baseBand;
private Complex syncPulse;
private Complex scanLine;
private int tint; private int tint;
private int curLine; private int curLine;
private int curColumn; private int curColumn;
@ -66,28 +55,22 @@ public class MainActivity extends AppCompatActivity {
@Override @Override
public void onPeriodicNotification(AudioRecord audioRecord) { public void onPeriodicNotification(AudioRecord audioRecord) {
audioRecord.read(recordBuffer, 0, recordBuffer.length, AudioRecord.READ_BLOCKING); audioRecord.read(recordBuffer, 0, recordBuffer.length, AudioRecord.READ_BLOCKING);
processSamples(); demodulator.process(recordBuffer);
visualizeSignal();
} }
}; };
private void processSamples() { private void visualizeSignal() {
for (float v : recordBuffer) { for (float v : recordBuffer) {
baseBand = baseBandLowPass.avg(baseBand.set(v).mul(baseBandOscillator.rotate())); int pixelColor = 0x00010101;
syncPulse = syncPulseFilter.avg(syncPulse.set(baseBand).mul(syncPulseOscillator.rotate())); float level = v;
scanLine = scanLineFilter.avg(scanLine.set(baseBand).mul(scanLineOscillator.rotate())); if (v < 0) {
float syncPulseValue = syncPulseDelay.push(syncPulse.norm()) / powerAvg.avg(baseBand.norm()); level = -v;
float scanLineValue = scanLineDelay.push(scanLineDemod.demod(scanLine)); pixelColor = 0x00000100;
float syncPulseLevel = Math.min(Math.max(syncPulseValue, 0), 1); }
float scanLineLevel = Math.min(Math.max(0.5f * (scanLineValue + 1), 0), 1); int intensity = (int) Math.round(255 * Math.sqrt(level));
int syncPulseIntensity = (int) Math.round(255 * Math.sqrt(syncPulseLevel)); pixelColor *= intensity;
int scanLineIntensity = (int) Math.round(255 * Math.sqrt(scanLineLevel)); pixelColor |= 0xff000000;
int syncPulseColor = 0x00000100 * syncPulseIntensity;
int scanLineColor = 0x00010101 * scanLineIntensity;
int pixelColor = 0xff000000;
if (syncPulseLevel > 0.1)
pixelColor |= syncPulseColor;
else
pixelColor |= scanLineColor;
scopePixels[scopeWidth * curLine + curColumn] = pixelColor; scopePixels[scopeWidth * curLine + curColumn] = pixelColor;
if (++curColumn >= scopeWidth) { if (++curColumn >= scopeWidth) {
curColumn = 0; curColumn = 0;
@ -100,40 +83,6 @@ public class MainActivity extends AppCompatActivity {
} }
} }
private void initTools(int sampleRate) {
double powerWindowSeconds = 0.5;
int powerWindowSamples = (int) Math.round(powerWindowSeconds * sampleRate) | 1;
powerAvg = new SimpleMovingAverage(powerWindowSamples);
float blackFrequency = 1500;
float whiteFrequency = 2300;
float scanLineBandwidth = whiteFrequency - blackFrequency;
scanLineDemod = new FrequencyModulation(scanLineBandwidth, sampleRate);
float scanLineCutoff = scanLineBandwidth / 2;
int scanLineFilterSamples = (int) Math.round(0.443 * sampleRate / scanLineCutoff) | 1;
scanLineFilter = new ComplexMovingAverage(scanLineFilterSamples);
double syncPulseSeconds = 0.009;
int syncPulseFilterSamples = (int) Math.round(syncPulseSeconds * sampleRate) | 1;
syncPulseFilter = new ComplexMovingAverage(syncPulseFilterSamples);
float lowestFrequency = 1100;
float highestFrequency = 2300;
float cutoffFrequency = (highestFrequency - lowestFrequency) / 2;
int lowPassSamples = (int) Math.round(0.443 * sampleRate / cutoffFrequency) | 1;
baseBandLowPass = new ComplexMovingAverage(lowPassSamples);
float centerFrequency = (lowestFrequency + highestFrequency) / 2;
baseBandOscillator = new Phasor(-centerFrequency, sampleRate);
float syncPulseFrequency = 1200;
syncPulseOscillator = new Phasor(-(syncPulseFrequency - centerFrequency), sampleRate);
float grayFrequency = (blackFrequency + whiteFrequency) / 2;
scanLineOscillator = new Phasor(-(grayFrequency - centerFrequency), sampleRate);
int syncPulseDelaySamples = (powerWindowSamples - 1) / 2;
syncPulseDelay = new Delay(syncPulseDelaySamples);
int scanLineDelaySamples = (powerWindowSamples - 1) / 2 + (syncPulseFilterSamples - 1) / 2 - (scanLineFilterSamples - 1) / 2;
scanLineDelay = new Delay(scanLineDelaySamples);
baseBand = new Complex();
syncPulse = new Complex();
scanLine = new Complex();
}
private void initAudioRecord() { private void initAudioRecord() {
int audioSource = MediaRecorder.AudioSource.UNPROCESSED; int audioSource = MediaRecorder.AudioSource.UNPROCESSED;
int channelConfig = AudioFormat.CHANNEL_IN_MONO; int channelConfig = AudioFormat.CHANNEL_IN_MONO;
@ -150,7 +99,7 @@ public class MainActivity extends AppCompatActivity {
if (audioRecord.getState() == AudioRecord.STATE_INITIALIZED) { if (audioRecord.getState() == AudioRecord.STATE_INITIALIZED) {
audioRecord.setRecordPositionUpdateListener(recordListener); audioRecord.setRecordPositionUpdateListener(recordListener);
audioRecord.setPositionNotificationPeriod(recordBuffer.length); audioRecord.setPositionNotificationPeriod(recordBuffer.length);
initTools(sampleRate); demodulator = new Demodulator(sampleRate);
startListening(); startListening();
} else { } else {
setStatus(R.string.audio_init_failed); setStatus(R.string.audio_init_failed);