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sdrangel/plugins/channelrx/demodrtty/rttydemodsink.cpp

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///////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2023 Jon Beniston, M7RCE <jon@beniston.com> //
// //
// 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 as 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 V3 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/>. //
///////////////////////////////////////////////////////////////////////////////////
#include <QDebug>
#include <QRegularExpression>
#include <complex.h>
#include "dsp/dspengine.h"
#include "dsp/scopevis.h"
#include "util/db.h"
#include "maincore.h"
#include "rttydemod.h"
#include "rttydemodsink.h"
RttyDemodSink::RttyDemodSink(RttyDemod *packetDemod) :
m_rttyDemod(packetDemod),
m_channelSampleRate(RttyDemodSettings::RTTYDEMOD_CHANNEL_SAMPLE_RATE),
m_channelFrequencyOffset(0),
m_magsqSum(0.0f),
m_magsqPeak(0.0f),
m_magsqCount(0),
m_messageQueueToChannel(nullptr),
m_expLength(600),
m_prods1(nullptr),
m_prods2(nullptr),
m_exp(nullptr),
m_sampleIdx(0),
m_clockHistogram(100),
m_shiftEstMag(m_fftSize),
m_fftSequence(-1),
m_fft(nullptr),
m_fftCounter(0),
m_sampleBufferIndex(0)
{
m_magsq = 0.0;
m_sampleBuffer.resize(m_sampleBufferSize);
applySettings(m_settings, true);
applyChannelSettings(m_channelSampleRate, m_channelFrequencyOffset, true);
FFTFactory *fftFactory = DSPEngine::instance()->getFFTFactory();
if (m_fftSequence >= 0) {
fftFactory->releaseEngine(m_fftSize, false, m_fftSequence);
}
m_fftSequence = fftFactory->getEngine(m_fftSize, false, &m_fft);
m_fftCounter = 0;
}
RttyDemodSink::~RttyDemodSink()
{
delete[] m_exp;
delete[] m_prods1;
delete[] m_prods2;
}
void RttyDemodSink::sampleToScope(Complex sample)
{
if (m_scopeSink)
{
Real r = std::real(sample) * SDR_RX_SCALEF;
Real i = std::imag(sample) * SDR_RX_SCALEF;
m_sampleBuffer[m_sampleBufferIndex++] = Sample(r, i);
if (m_sampleBufferIndex == m_sampleBufferSize)
{
std::vector<SampleVector::const_iterator> vbegin;
vbegin.push_back(m_sampleBuffer.begin());
m_scopeSink->feed(vbegin, m_sampleBufferSize);
m_sampleBufferIndex = 0;
}
}
}
void RttyDemodSink::feed(const SampleVector::const_iterator& begin, const SampleVector::const_iterator& end)
{
Complex ci;
for (SampleVector::const_iterator it = begin; it != end; ++it)
{
Complex c(it->real(), it->imag());
c *= m_nco.nextIQ();
if (m_interpolatorDistance < 1.0f) // interpolate
{
while (!m_interpolator.interpolate(&m_interpolatorDistanceRemain, c, &ci))
{
processOneSample(ci);
m_interpolatorDistanceRemain += m_interpolatorDistance;
}
}
else // decimate
{
if (m_interpolator.decimate(&m_interpolatorDistanceRemain, c, &ci))
{
processOneSample(ci);
m_interpolatorDistanceRemain += m_interpolatorDistance;
}
}
}
}
void RttyDemodSink::processOneSample(Complex &ci)
{
// Calculate average and peak levels for level meter
double magsqRaw = ci.real()*ci.real() + ci.imag()*ci.imag();;
Real magsq = magsqRaw / (SDR_RX_SCALED*SDR_RX_SCALED);
m_movingAverage(magsq);
m_magsq = m_movingAverage.asDouble();
m_magsqSum += magsq;
if (magsq > m_magsqPeak)
{
m_magsqPeak = magsq;
}
m_magsqCount++;
// Sum power while data is being received
if (m_gotSOP)
{
m_rssiMagSqSum += magsq;
m_rssiMagSqCount++;
}
ci /= SDR_RX_SCALEF;
// Use FFT to estimate frequency shift
m_fft->in()[m_fftCounter] = ci;
m_fftCounter++;
if (m_fftCounter == m_fftSize)
{
estimateFrequencyShift();
m_fftCounter = 0;
}
// Correlate with expected mark and space frequencies
Complex exp = m_exp[m_expIdx];
m_expIdx = (m_expIdx + 1) % m_expLength;
//Complex exp = m_exp[m_sampleIdx];
//qDebug() << "IQ " << real(ci) << imag(ci);
Complex corr1 = ci * std::conj(exp); // Conj is high/mark freq (as for matched filter, we need to time reverse and take conjugate)
Complex corr2 = ci * exp; // Low/space freq
// Filter
Real abs1, abs2;
Real abs1Filt, abs2Filt;
if (m_settings.m_filter == RttyDemodSettings::LOWPASS)
{
// Low pass filter
abs1Filt = abs1 = std::abs(m_lowpassComplex1.filter(corr1));
abs2Filt = abs2 = std::abs(m_lowpassComplex2.filter(corr2));
}
else if ( (m_settings.m_filter == RttyDemodSettings::COSINE_B_1)
|| (m_settings.m_filter == RttyDemodSettings::COSINE_B_0_75)
|| (m_settings.m_filter == RttyDemodSettings::COSINE_B_0_5)
)
{
// Rasised cosine filter
abs1Filt = abs1 = std::abs(m_raisedCosine1.filter(corr1));
abs2Filt = abs2 = std::abs(m_raisedCosine2.filter(corr2));
}
else
{
// Moving average
// Calculating moving average (well windowed sum)
Complex old1 = m_prods1[m_sampleIdx];
Complex old2 = m_prods2[m_sampleIdx];
m_prods1[m_sampleIdx] = corr1;
m_prods2[m_sampleIdx] = corr2;
m_sum1 += m_prods1[m_sampleIdx] - old1;
m_sum2 += m_prods2[m_sampleIdx] - old2;
m_sampleIdx = (m_sampleIdx + 1) % m_samplesPerBit;
// Square signals (by calculating absolute value of complex signal)
abs1 = std::abs(m_sum1);
abs2 = std::abs(m_sum2);
// Apply optional low-pass filter to try to avoid extra zero-crassings above the baud rate
if (m_settings.m_filter == RttyDemodSettings::FILTERED_MAV)
{
abs1Filt = m_lowpass1.filter(abs1);
abs2Filt = m_lowpass2.filter(abs2);
}
else
{
abs1Filt = abs1;
abs2Filt = abs2;
}
}
// Envelope calculation
m_movMax1(abs1Filt);
m_movMax2(abs2Filt);
Real env1 = m_movMax1.getMaximum();
Real env2 = m_movMax2.getMaximum();
// Automatic threshold correction to compensate for frequency selective fading
// http://www.w7ay.net/site/Technical/ATC/index.html
Real bias1 = abs1Filt - 0.5 * env1;
Real bias2 = abs2Filt - 0.5 * env2;
Real unbiasedData = abs1Filt - abs2Filt;
Real biasedData = bias1 - bias2;
// Save current data for edge detection
m_dataPrev = m_data;
// Set data according to stongest correlation
if (m_settings.m_spaceHigh) {
m_data = m_settings.m_atc ? biasedData < 0 : unbiasedData < 0;
} else {
m_data = m_settings.m_atc ? biasedData > 0 : unbiasedData > 0;
}
if (!m_gotSOP)
{
// Look for falling edge which indicates start bit
if (!m_data && m_dataPrev)
{
m_gotSOP = true;
m_bits = 0;
m_bitCount = 0;
m_clockCount = 0;
m_clock = false;
m_cycleCount = 0;
m_rssiMagSqSum = 0.0;
m_rssiMagSqCount = 0;
}
}
else
{
// Sample in middle of symbol
if (m_clockCount == m_samplesPerBit/2)
{
receiveBit(m_data);
m_clock = true;
}
m_clockCount = (m_clockCount + 1) % m_samplesPerBit;
if (m_clockCount == 0) {
m_clock = false;
}
// Count cycles between edges, to estimate baud rate
m_cycleCount++;
if (m_data != m_dataPrev)
{
if (m_cycleCount < m_clockHistogram.size())
{
m_clockHistogram[m_cycleCount]++;
m_edgeCount++;
// Every 100 edges, calculate estimate
if (m_edgeCount == 100) {
estimateBaudRate();
}
}
m_cycleCount = 0;
}
}
// Select signals to feed to scope
Complex scopeSample;
switch (m_settings.m_scopeCh1)
{
case 0:
scopeSample.real(ci.real());
break;
case 1:
scopeSample.real(ci.imag());
break;
case 2:
scopeSample.real(magsq);
break;
case 3:
scopeSample.real(m_sampleIdx);
break;
case 4:
scopeSample.real(abs(m_sum1));
break;
case 5:
scopeSample.real(abs(m_sum2));
break;
case 6:
scopeSample.real(m_bit);
break;
case 7:
scopeSample.real(m_bitCount);
break;
case 8:
scopeSample.real(m_gotSOP);
break;
case 9:
scopeSample.real(real(exp));
break;
case 10:
scopeSample.real(imag(exp));
break;
case 11:
scopeSample.real(abs1Filt);
break;
case 12:
scopeSample.real(abs2Filt);
break;
case 13:
scopeSample.real(abs2 - abs1);
break;
case 14:
scopeSample.real(abs2Filt - abs1Filt);
break;
case 15:
scopeSample.real(m_data);
break;
case 16:
scopeSample.real(m_clock);
break;
case 17:
scopeSample.real(env1);
break;
case 18:
scopeSample.real(env2);
break;
case 19:
scopeSample.real(bias1);
break;
case 20:
scopeSample.real(bias2);
break;
case 21:
scopeSample.real(unbiasedData);
break;
case 22:
scopeSample.real(biasedData);
break;
}
switch (m_settings.m_scopeCh2)
{
case 0:
scopeSample.imag(ci.real());
break;
case 1:
scopeSample.imag(ci.imag());
break;
case 2:
scopeSample.imag(magsq);
break;
case 3:
scopeSample.imag(m_sampleIdx);
break;
case 4:
scopeSample.imag(abs(m_sum1));
break;
case 5:
scopeSample.imag(abs(m_sum2));
break;
case 6:
scopeSample.imag(m_bit);
break;
case 7:
scopeSample.imag(m_bitCount);
break;
case 8:
scopeSample.imag(m_gotSOP);
break;
case 9:
scopeSample.imag(real(exp));
break;
case 10:
scopeSample.imag(imag(exp));
break;
case 11:
scopeSample.imag(abs1Filt);
break;
case 12:
scopeSample.imag(abs2Filt);
break;
case 13:
scopeSample.imag(abs2 - abs1);
break;
case 14:
scopeSample.imag(abs2Filt - abs1Filt);
break;
case 15:
scopeSample.imag(m_data);
break;
case 16:
scopeSample.imag(m_clock);
break;
case 17:
scopeSample.imag(env1);
break;
case 18:
scopeSample.imag(env2);
break;
case 19:
scopeSample.imag(bias1);
break;
case 20:
scopeSample.imag(bias2);
break;
case 21:
scopeSample.imag(unbiasedData);
break;
case 22:
scopeSample.imag(biasedData);
break;
}
sampleToScope(scopeSample);
}
void RttyDemodSink::estimateFrequencyShift()
{
// Perform FFT
m_fft->transform();
// Calculate magnitude
for (int i = 0; i < m_fftSize; i++)
{
Complex c = m_fft->out()[i];
Real v = c.real() * c.real() + c.imag() * c.imag();
Real magsq = v / (m_fftSize * m_fftSize);
m_shiftEstMag[i] = magsq;
}
// Fink peaks in each half
Real peak1 = m_shiftEstMag[0];
int peak1Bin = 0;
for (int i = 1; i < m_fftSize/2; i++)
{
if (m_shiftEstMag[i] > peak1)
{
peak1 = m_shiftEstMag[i];
peak1Bin = i;
}
}
Real peak2 = m_shiftEstMag[m_fftSize/2];
int peak2Bin = m_fftSize/2;
for (int i = m_fftSize/2+1; i < m_fftSize; i++)
{
if (m_shiftEstMag[i] > peak2)
{
peak2 = m_shiftEstMag[i];
peak2Bin = i;
}
}
// Convert bin to frequency offset
double frequencyResolution = RttyDemodSettings::RTTYDEMOD_CHANNEL_SAMPLE_RATE / (double)m_fftSize;
double freq1 = frequencyResolution * peak1Bin;
double freq2 = -frequencyResolution * (m_fftSize - peak2Bin);
m_freq1Average(freq1);
m_freq2Average(freq2);
//int shift = m_freq1Average.instantAverage() - m_freq2Average.instantAverage();
//qDebug() << "Freq est " << freq1 << freq2 << shift;
}
int RttyDemodSink::estimateBaudRate()
{
// Find most frequent entry in histogram
auto histMax = max_element(m_clockHistogram.begin(), m_clockHistogram.end());
int index = std::distance(m_clockHistogram.begin(), histMax);
// Calculate baud rate as weighted average
Real baud1 = RttyDemodSettings::RTTYDEMOD_CHANNEL_SAMPLE_RATE / (Real)(index-1);
int count1 = m_clockHistogram[index-1];
Real baud2 = RttyDemodSettings::RTTYDEMOD_CHANNEL_SAMPLE_RATE / (Real)(index);
int count2 = m_clockHistogram[index];
Real baud3 = RttyDemodSettings::RTTYDEMOD_CHANNEL_SAMPLE_RATE / (Real)(index+1);
int count3 = m_clockHistogram[index+1];
Real total = count1 + count2 + count3;
Real estBaud = count1/total*baud1 + count2/total*baud2 + count3/total*baud3;
m_baudRateAverage(estBaud);
// Send estimate to GUI
if (getMessageQueueToChannel())
{
int estFrequencyShift = m_freq1Average.instantAverage() - m_freq2Average.instantAverage();
RttyDemod::MsgModeEstimate *msg = RttyDemod::MsgModeEstimate::create(m_baudRateAverage.instantAverage(), estFrequencyShift);
getMessageQueueToChannel()->push(msg);
}
// Restart estimation
std::fill(m_clockHistogram.begin(), m_clockHistogram.end(), 0);
m_edgeCount = 0;
return estBaud;
}
void RttyDemodSink::receiveBit(bool bit)
{
m_bit = bit;
// Store in shift reg.
if (m_settings.m_msbFirst) {
m_bits = (m_bit & 0x1) | (m_bits << 1);
} else {
m_bits = (m_bit << 6) | (m_bits >> 1);
}
m_bitCount++;
if (m_bitCount == 7)
{
if ( (!m_settings.m_msbFirst && ((m_bits & 0x40) != 0x40))
|| (m_settings.m_msbFirst && ((m_bits & 0x01) != 0x01)))
{
//qDebug() << "No stop bit";
}
else
{
QString c = m_rttyDecoder.decode((m_bits >> 1) & 0x1f);
if ((c != "\0") && (c != "<") && (c != ">") && (c != "^"))
{
// Calculate average power over received byte
float rssi = CalcDb::dbPower(m_rssiMagSqSum / m_rssiMagSqCount);
if (rssi > m_settings.m_squelch)
{
// Slow enough to send individually to be displayed
if (getMessageQueueToChannel())
{
RttyDemod::MsgCharacter *msg = RttyDemod::MsgCharacter::create(c);
getMessageQueueToChannel()->push(msg);
}
}
}
}
m_gotSOP = false;
}
}
void RttyDemodSink::applyChannelSettings(int channelSampleRate, int channelFrequencyOffset, bool force)
{
qDebug() << "RttyDemodSink::applyChannelSettings:"
<< " channelSampleRate: " << channelSampleRate
<< " channelFrequencyOffset: " << channelFrequencyOffset;
if ((m_channelFrequencyOffset != channelFrequencyOffset) ||
(m_channelSampleRate != channelSampleRate) || force)
{
m_nco.setFreq(-channelFrequencyOffset, channelSampleRate);
}
if ((m_channelSampleRate != channelSampleRate) || force)
{
m_interpolator.create(16, channelSampleRate, m_settings.m_rfBandwidth / 2.2);
m_interpolatorDistance = (Real) channelSampleRate / (Real) RttyDemodSettings::RTTYDEMOD_CHANNEL_SAMPLE_RATE;
m_interpolatorDistanceRemain = m_interpolatorDistance;
}
m_channelSampleRate = channelSampleRate;
m_channelFrequencyOffset = channelFrequencyOffset;
}
void RttyDemodSink::init()
{
m_sampleIdx = 0;
m_expIdx = 0;
m_sum1 = 0.0;
m_sum2 = 0.0;
for (int i = 0; i < m_samplesPerBit; i++)
{
m_prods1[i] = 0.0f;
m_prods2[i] = 0.0f;
}
m_bit = 0;
m_bits = 0;
m_bitCount = 0;
m_gotSOP = false;
m_clockCount = 0;
m_clock = 0;
m_rssiMagSqSum = 0.0;
m_rssiMagSqCount = 0;
m_rttyDecoder.init();
}
void RttyDemodSink::applySettings(const RttyDemodSettings& settings, bool force)
{
qDebug() << "RttyDemodSink::applySettings:"
<< " m_rfBandwidth: " << settings.m_rfBandwidth
<< " m_baudRate: " << settings.m_baudRate
<< " m_frequencyShift: " << settings.m_frequencyShift
<< " m_characterSet: " << settings.m_characterSet
<< " m_unshiftOnSpace: " << settings.m_unshiftOnSpace
<< " force: " << force;
if ((settings.m_rfBandwidth != m_settings.m_rfBandwidth) || force)
{
m_interpolator.create(16, m_channelSampleRate, settings.m_rfBandwidth / 2.2);
m_interpolatorDistance = (Real) m_channelSampleRate / (Real) RttyDemodSettings::RTTYDEMOD_CHANNEL_SAMPLE_RATE;
m_interpolatorDistanceRemain = m_interpolatorDistance;
}
if ((settings.m_baudRate != m_settings.m_baudRate) || (settings.m_filter != m_settings.m_filter) || force)
{
m_envelope1.create(301, RttyDemodSettings::RTTYDEMOD_CHANNEL_SAMPLE_RATE, 2);
m_envelope2.create(301, RttyDemodSettings::RTTYDEMOD_CHANNEL_SAMPLE_RATE, 2);
m_lowpass1.create(301, RttyDemodSettings::RTTYDEMOD_CHANNEL_SAMPLE_RATE, m_settings.m_baudRate * 1.1);
m_lowpass2.create(301, RttyDemodSettings::RTTYDEMOD_CHANNEL_SAMPLE_RATE, m_settings.m_baudRate * 1.1);
//m_lowpass1.printTaps("lpf");
m_lowpassComplex1.create(301, RttyDemodSettings::RTTYDEMOD_CHANNEL_SAMPLE_RATE, m_settings.m_baudRate * 1.1);
m_lowpassComplex2.create(301, RttyDemodSettings::RTTYDEMOD_CHANNEL_SAMPLE_RATE, m_settings.m_baudRate * 1.1);
//m_lowpass1.printTaps("lpfc");
// http://w7ay.net/site/Technical/Extended%20Nyquist%20Filters/index.html
// http://w7ay.net/site/Technical/EqualizedRaisedCosine/index.html
float beta = 1.0f;
float bw = 1.0f;
if (settings.m_filter == RttyDemodSettings::COSINE_B_0_5) {
beta = 0.5f;
} else if (settings.m_filter == RttyDemodSettings::COSINE_B_0_75) {
beta = 0.75f;
} else if (settings.m_filter == RttyDemodSettings::COSINE_B_1_BW_0_75) {
bw = 0.75f;
} else if (settings.m_filter == RttyDemodSettings::COSINE_B_1_BW_1_25) {
bw = 1.25f;
}
m_raisedCosine1.create(beta, 7, RttyDemodSettings::RTTYDEMOD_CHANNEL_SAMPLE_RATE/(m_settings.m_baudRate/bw), false);
m_raisedCosine2.create(beta, 7, RttyDemodSettings::RTTYDEMOD_CHANNEL_SAMPLE_RATE/(m_settings.m_baudRate/bw), false);
//m_raisedCosine1.printTaps("rcos");
}
if ((settings.m_characterSet != m_settings.m_characterSet) || force) {
m_rttyDecoder.setCharacterSet(settings.m_characterSet);
}
if ((settings.m_unshiftOnSpace != m_settings.m_unshiftOnSpace) || force) {
m_rttyDecoder.setUnshiftOnSpace(settings.m_unshiftOnSpace);
}
if ((settings.m_baudRate != m_settings.m_baudRate) || (settings.m_frequencyShift != m_settings.m_frequencyShift) || force)
{
delete[] m_exp;
delete[] m_prods1;
delete[] m_prods2;
m_samplesPerBit = RttyDemodSettings::RTTYDEMOD_CHANNEL_SAMPLE_RATE / settings.m_baudRate;
m_exp = new Complex[m_expLength];
m_prods1 = new Complex[m_samplesPerBit];
m_prods2 = new Complex[m_samplesPerBit];
Real f0 = 0.0f;
for (int i = 0; i < m_expLength; i++)
{
m_exp[i] = Complex(cos(f0), sin(f0));
f0 += 2.0f * (Real)M_PI * (settings.m_frequencyShift/2.0f) / RttyDemodSettings::RTTYDEMOD_CHANNEL_SAMPLE_RATE;
}
init();
// Due to start and stop bits, we should get mark and space at least every 8 bits
// while something is being transmitted
m_movMax1.setSize(m_samplesPerBit * 8);
m_movMax2.setSize(m_samplesPerBit * 8);
m_edgeCount = 0;
std::fill(m_clockHistogram.begin(), m_clockHistogram.end(), 0);
m_baudRateAverage.reset();
m_freq1Average.reset();
m_freq2Average.reset();
}
m_settings = settings;
}
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