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SSB demod: added FIR LP filter after AGC to smooth out sharp peaks

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This commit is contained in:
f4exb 2023-12-09 12:53:39 +01:00
parent d97f92dcc3
commit aee055e883
2 changed files with 15 additions and 1 deletions
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12
plugins/channelrx/demodssb/ssbdemodsink.cpp
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@ -82,6 +82,9 @@ SSBDemodSink::SSBDemodSink() :
SSBFilter = new fftfilt(m_LowCutoff / m_audioSampleRate, m_Bandwidth / m_audioSampleRate, m_ssbFftLen); SSBFilter = new fftfilt(m_LowCutoff / m_audioSampleRate, m_Bandwidth / m_audioSampleRate, m_ssbFftLen);
DSBFilter = new fftfilt((2.0f * m_Bandwidth) / m_audioSampleRate, 2 * m_ssbFftLen); DSBFilter = new fftfilt((2.0f * m_Bandwidth) / m_audioSampleRate, 2 * m_ssbFftLen);
m_lowpassI.create(101, m_audioSampleRate, m_Bandwidth * 1.2);
m_lowpassQ.create(101, m_audioSampleRate, m_Bandwidth * 1.2);
applyChannelSettings(m_channelSampleRate, m_channelFrequencyOffset, true); applyChannelSettings(m_channelSampleRate, m_channelFrequencyOffset, true);
applySettings(m_settings, true); applySettings(m_settings, true);
} }
@ -201,7 +204,9 @@ void SSBDemodSink::processOneSample(Complex &ci)
else else
{ {
// fftfilt::cmplx z = m_agcActive ? delayedSample * m_agc.getStepValue() : delayedSample; // fftfilt::cmplx z = m_agcActive ? delayedSample * m_agc.getStepValue() : delayedSample;
fftfilt::cmplx& z = delayedSample; fftfilt::cmplx z = (m_agcActive && m_agcClamping) ?
fftfilt::cmplx{m_lowpassI.filter(delayedSample.real()), m_lowpassQ.filter(delayedSample.imag())}
: delayedSample;
if (m_audioBinaual) if (m_audioBinaual)
{ {
@ -318,6 +323,9 @@ void SSBDemodSink::applyAudioSampleRate(int sampleRate)
SSBFilter->create_filter(m_LowCutoff / (float) sampleRate, m_Bandwidth / (float) sampleRate, m_settings.m_filterBank[m_settings.m_filterIndex].m_fftWindow); SSBFilter->create_filter(m_LowCutoff / (float) sampleRate, m_Bandwidth / (float) sampleRate, m_settings.m_filterBank[m_settings.m_filterIndex].m_fftWindow);
DSBFilter->create_dsb_filter(m_Bandwidth / (float) sampleRate, m_settings.m_filterBank[m_settings.m_filterIndex].m_fftWindow); DSBFilter->create_dsb_filter(m_Bandwidth / (float) sampleRate, m_settings.m_filterBank[m_settings.m_filterIndex].m_fftWindow);
m_lowpassI.create(101, sampleRate, m_Bandwidth * 1.2);
m_lowpassQ.create(101, sampleRate, m_Bandwidth * 1.2);
int agcNbSamples = (sampleRate / 1000) * (1<<m_settings.m_agcTimeLog2); int agcNbSamples = (sampleRate / 1000) * (1<<m_settings.m_agcTimeLog2);
int agcThresholdGate = (sampleRate / 1000) * m_settings.m_agcThresholdGate; // ms int agcThresholdGate = (sampleRate / 1000) * m_settings.m_agcThresholdGate; // ms
@ -423,6 +431,8 @@ void SSBDemodSink::applySettings(const SSBDemodSettings& settings, bool force)
m_interpolatorDistance = (Real) m_channelSampleRate / (Real) m_audioSampleRate; m_interpolatorDistance = (Real) m_channelSampleRate / (Real) m_audioSampleRate;
SSBFilter->create_filter(m_LowCutoff / (float) m_audioSampleRate, m_Bandwidth / (float) m_audioSampleRate, settings.m_filterBank[settings.m_filterIndex].m_fftWindow); SSBFilter->create_filter(m_LowCutoff / (float) m_audioSampleRate, m_Bandwidth / (float) m_audioSampleRate, settings.m_filterBank[settings.m_filterIndex].m_fftWindow);
DSBFilter->create_dsb_filter(m_Bandwidth / (float) m_audioSampleRate, settings.m_filterBank[settings.m_filterIndex].m_fftWindow); DSBFilter->create_dsb_filter(m_Bandwidth / (float) m_audioSampleRate, settings.m_filterBank[settings.m_filterIndex].m_fftWindow);
m_lowpassI.create(101, m_audioSampleRate, m_Bandwidth * 1.2);
m_lowpassQ.create(101, m_audioSampleRate, m_Bandwidth * 1.2);
} }
if ((m_settings.m_volume != settings.m_volume) || force) if ((m_settings.m_volume != settings.m_volume) || force)

4
plugins/channelrx/demodssb/ssbdemodsink.h
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@ -25,6 +25,7 @@
#include "dsp/interpolator.h" #include "dsp/interpolator.h"
#include "dsp/fftfilt.h" #include "dsp/fftfilt.h"
#include "dsp/agc.h" #include "dsp/agc.h"
#include "dsp/firfilter.h"
#include "audio/audiofifo.h" #include "audio/audiofifo.h"
#include "util/doublebufferfifo.h" #include "util/doublebufferfifo.h"
@ -112,6 +113,9 @@ private:
int m_agcThresholdGate; //!< Gate length in number of samples befor threshold triggers int m_agcThresholdGate; //!< Gate length in number of samples befor threshold triggers
DoubleBufferFIFO<fftfilt::cmplx> m_squelchDelayLine; DoubleBufferFIFO<fftfilt::cmplx> m_squelchDelayLine;
bool m_audioActive; //!< True if an audio signal is produced (no AGC or AGC and above threshold) bool m_audioActive; //!< True if an audio signal is produced (no AGC or AGC and above threshold)
Lowpass<Real> m_lowpassI;
Lowpass<Real> m_lowpassQ;
NCOF m_nco; NCOF m_nco;
Interpolator m_interpolator; Interpolator m_interpolator;