From 064f25ee73148580fe26fd817b97dd1fa3f11f99 Mon Sep 17 00:00:00 2001 From: AlexandreRouma Date: Thu, 19 Sep 2024 17:28:03 +0200 Subject: [PATCH] work on the time sync algo --- decoder_modules/dab_decoder/src/ofdm.h | 121 +++++++++++++++++-------- 1 file changed, 85 insertions(+), 36 deletions(-) diff --git a/decoder_modules/dab_decoder/src/ofdm.h b/decoder_modules/dab_decoder/src/ofdm.h index 4934bd5a..1f3fb5a5 100644 --- a/decoder_modules/dab_decoder/src/ofdm.h +++ b/decoder_modules/dab_decoder/src/ofdm.h @@ -6,29 +6,33 @@ #include namespace dsp::ofdm { - class MM : public Processor { + class CyclicTimeSync : public Processor { using base_type = Processor ; public: - MM() {} + CyclicTimeSync() {} - MM(stream* in, double omega, double omegaGain, double muGain, double omegaRelLimit, int interpPhaseCount = 128, int interpTapCount = 8) { init(in, omega, omegaGain, muGain, omegaRelLimit, interpPhaseCount, interpTapCount); } + CyclicTimeSync(stream* in, int fftSize, double usefulSymbolTime, double cyclicPrefixRatio, double samplerate, + double omegaGain, double muGain, double omegaRelLimit, int interpPhaseCount = 128, int interpTapCount = 8) { + init(in, fftSize, usefulSymbolTime, cyclicPrefixRatio, samplerate, omegaGain, muGain, omegaRelLimit, interpPhaseCount, interpTapCount); + } - ~MM() { + ~CyclicTimeSync() { if (!base_type::_block_init) { return; } base_type::stop(); dsp::multirate::freePolyphaseBank(interpBank); buffer::free(buffer); } - void init(stream* in, double omega, double omegaGain, double muGain, double omegaRelLimit, int interpPhaseCount = 128, int interpTapCount = 8) { - _omega = omega; + void init(stream* in, int fftSize, double usefulSymbolTime, double cyclicPrefixRatio, double samplerate, + double omegaGain, double muGain, double omegaRelLimit, int interpPhaseCount = 128, int interpTapCount = 8) { + omega = 0; // TODO _omegaGain = omegaGain; _muGain = muGain; _omegaRelLimit = omegaRelLimit; _interpPhaseCount = interpPhaseCount; _interpTapCount = interpTapCount; - pcl.init(_muGain, _omegaGain, 0.0, 0.0, 1.0, _omega, _omega * (1.0 - omegaRelLimit), _omega * (1.0 + omegaRelLimit)); + pcl.init(_muGain, _omegaGain, 0.0, 0.0, 1.0, omega, omega * (1.0 - omegaRelLimit), omega * (1.0 + omegaRelLimit)); generateInterpTaps(); buffer = buffer::alloc(STREAM_BUFFER_SIZE + _interpTapCount); bufStart = &buffer[_interpTapCount - 1]; @@ -36,18 +40,6 @@ namespace dsp::ofdm { base_type::init(in); } - void setOmega(double omega) { - assert(base_type::_block_init); - std::lock_guard lck(base_type::ctrlMtx); - base_type::tempStop(); - _omega = omega; - offset = 0; - pcl.phase = 0.0f; - pcl.freq = _omega; - pcl.setFreqLimits(_omega * (1.0 - _omegaRelLimit), _omega * (1.0 + _omegaRelLimit)); - base_type::tempStart(); - } - void setOmegaGain(double omegaGain) { assert(base_type::_block_init); std::lock_guard lck(base_type::ctrlMtx); @@ -66,7 +58,7 @@ namespace dsp::ofdm { assert(base_type::_block_init); std::lock_guard lck(base_type::ctrlMtx); _omegaRelLimit = omegaRelLimit; - pcl.setFreqLimits(_omega * (1.0 - _omegaRelLimit), _omega * (1.0 + _omegaRelLimit)); + pcl.setFreqLimits(omega * (1.0 - _omegaRelLimit), omega * (1.0 + _omegaRelLimit)); } void setInterpParams(int interpPhaseCount, int interpTapCount) { @@ -89,7 +81,7 @@ namespace dsp::ofdm { base_type::tempStop(); offset = 0; pcl.phase = 0.0f; - pcl.freq = _omega; + pcl.freq = omega; base_type::tempStart(); } @@ -100,20 +92,60 @@ namespace dsp::ofdm { // Process all samples int outCount = 0; while (offset < count) { - float error = 0; // TODO - complex_t outVal; - - // Calculate new output value + // Compute the interpolated sample + complex_t sample; int phase = std::clamp(floorf(pcl.phase * (float)_interpPhaseCount), 0, _interpPhaseCount - 1); - volk_32fc_32f_dot_prod_32fc((lv_32fc_t*)&outVal, (lv_32fc_t*)&buffer[offset], interpBank.phases[phase], _interpTapCount); - out[outCount++] = outVal; + volk_32fc_32f_dot_prod_32fc((lv_32fc_t*)&sample, (lv_32fc_t*)&buffer[offset], interpBank.phases[phase], _interpTapCount); - // Advance symbol offset and phase - pcl.advance(error); + // Update autocorrelation + + // Compute the correlation level + float corrLvl = corr.amplitude(); + + // Detect peak in autocorrelation + if (0/*TODO*/) { + // Save the current correlation as the peak + corrPeak = corrLvl; + + // Save the value of the previous correlation as the left side of the peak + corrPeakL = corrLastLvl; + + // Save the symbol period + measuredSymbolPeriod = sampCount; + + // Reset the sample count + sampCount = 0; + + // TODO: Maybe save the error to apply it at the end of the frame? (will cause issues with the longer null symbol in DAB) + } + + // Write the sample to the frame if within it + if (sampCount < symbolSize) { + symbol[sampCount++] = sample; + } + + // When the end of the symbol is reached + if (sampCount == symbolSize) { + // Send out the symbol + // TODO + } + + // TODO: limit how much the sample count can grow otherwise otherflows will trigger a false frame detection + + // Run the control loop + //pcl.advance(error); // TODO + pcl.advancePhase(); + + // Update the offset and phase float delta = floorf(pcl.phase); offset += delta; pcl.phase -= delta; + + // Update the last correlation level + corrLastLvl = corrLvl; } + + // Prepare offset for next buffer of samples offset -= count; // Update delay buffer @@ -144,18 +176,35 @@ namespace dsp::ofdm { taps::free(lp); } + // Interpolator dsp::multirate::PolyphaseBank interpBank; + int _interpPhaseCount; + int _interpTapCount; + int offset = 0; + complex_t* buffer = NULL; + complex_t* bufStart; + + // Control loop loop::PhaseControlLoop pcl; - - double _omega; + double omega; double _omegaGain; double _muGain; double _omegaRelLimit; - int _interpPhaseCount; - int _interpTapCount; + + // Autocorrelator + complex_t corr; + complex_t* corrProducts = NULL; + float corrAgcRate; + float corrAgcInvRate; + float corrLastLvl = 0; + float corrPeakR = 0; + float corrPeak = 0; + float corrPeakL = 0; - int offset = 0; - complex_t* buffer; - complex_t* bufStart; + // Symbol + complex_t* symbol; // TODO: Will use output stream buffer instead + int symbolSize; + int sampCount = 0; + int measuredSymbolPeriod = 0; }; }; \ No newline at end of file