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SSB demod: mitigate AGC steep transitions causing audio clicks

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This commit is contained in:
f4exb 2023-11-30 14:11:36 +01:00
parent 3b969ac058
commit b402739db6
3 changed files with 24 additions and 5 deletions
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26
plugins/channelrx/demodssb/ssbdemodsink.cpp
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@ -69,10 +69,12 @@ SSBDemodSink::SSBDemodSink() :
m_demodBufferFill = 0; m_demodBufferFill = 0;
m_usb = true; m_usb = true;
m_magsq = 0.0f; m_magsq = 0.0;
m_magsqSum = 0.0f; m_magsqSum = 0.0;
m_magsqPeak = 0.0f; m_magsqPeak = 0.0;
m_magsqCount = 0; m_magsqCount = 0;
m_magsqCur = 0.0;
m_magsqPrev = 0.0;
m_agc.setClampMax(SDR_RX_SCALED/100.0); m_agc.setClampMax(SDR_RX_SCALED/100.0);
m_agc.setClamping(m_agcClamping); m_agc.setClamping(m_agcClamping);
@ -170,10 +172,24 @@ void SSBDemodSink::processOneSample(Complex &ci)
m_sum.imag(0.0); m_sum.imag(0.0);
} }
float agcVal = m_agcActive ? m_agc.feedAndGetValue(sideband[i]) : 0.1; float agcVal = m_agcActive ? m_agc.feedAndGetValue(sideband[i]) : 1.0;
fftfilt::cmplx& delayedSample = m_squelchDelayLine.readBack(m_agc.getStepDownDelay()); fftfilt::cmplx& delayedSample = m_squelchDelayLine.readBack(m_agc.getStepDownDelay());
m_audioActive = delayedSample.real() != 0.0; m_audioActive = delayedSample.real() != 0.0;
m_squelchDelayLine.write(sideband[i]*agcVal); m_magsqCur = std::norm(sideband[i]*agcVal);
// Prevent overload if squared magnitude variation is 90% full scale (0.9*.0.9 = 0.81)
// Only if AGC is active
if (m_agcActive && (m_magsqCur - m_magsqPrev > m_agcTarget*m_agcTarget*8.1))
{
m_agc.reset(m_agcTarget*100.0); // Quench AGC at -20dB the target
m_squelchDelayLine.write(sideband[i]);
}
else
{
m_squelchDelayLine.write(sideband[i]*agcVal);
}
m_magsqPrev = m_magsqCur;
if (m_audioMute) if (m_audioMute)
{ {

2
plugins/channelrx/demodssb/ssbdemodsink.h
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@ -101,6 +101,8 @@ private:
double m_magsqSum; double m_magsqSum;
double m_magsqPeak; double m_magsqPeak;
int m_magsqCount; int m_magsqCount;
double m_magsqCur;
double m_magsqPrev;
MagSqLevelsStore m_magSqLevelStore; MagSqLevelsStore m_magSqLevelStore;
MagAGC m_agc; MagAGC m_agc;
bool m_agcActive; bool m_agcActive;

1
sdrbase/dsp/agc.h
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@ -32,6 +32,7 @@ public:
void setOrder(double R) { m_R = R; } void setOrder(double R) { m_R = R; }
Real getValue(); Real getValue();
Real getAverage(); Real getAverage();
void reset(double R) { m_moving_average.fill(R); }
virtual void feed(Complex& ci) = 0; virtual void feed(Complex& ci) = 0;
protected: protected: