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SSB demod: mitigate AGC steep transitions causing audio clicks
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@ -69,10 +69,12 @@ SSBDemodSink::SSBDemodSink() :
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m_demodBufferFill = 0;
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m_usb = true;
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m_magsq = 0.0f;
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m_magsqSum = 0.0f;
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m_magsqPeak = 0.0f;
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m_magsq = 0.0;
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m_magsqSum = 0.0;
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m_magsqPeak = 0.0;
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m_magsqCount = 0;
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m_magsqCur = 0.0;
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m_magsqPrev = 0.0;
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m_agc.setClampMax(SDR_RX_SCALED/100.0);
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m_agc.setClamping(m_agcClamping);
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@ -170,10 +172,24 @@ void SSBDemodSink::processOneSample(Complex &ci)
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m_sum.imag(0.0);
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}
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float agcVal = m_agcActive ? m_agc.feedAndGetValue(sideband[i]) : 0.1;
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float agcVal = m_agcActive ? m_agc.feedAndGetValue(sideband[i]) : 1.0;
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fftfilt::cmplx& delayedSample = m_squelchDelayLine.readBack(m_agc.getStepDownDelay());
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m_audioActive = delayedSample.real() != 0.0;
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m_magsqCur = std::norm(sideband[i]*agcVal);
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// Prevent overload if squared magnitude variation is 90% full scale (0.9*.0.9 = 0.81)
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// Only if AGC is active
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if (m_agcActive && (m_magsqCur - m_magsqPrev > m_agcTarget*m_agcTarget*8.1))
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{
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m_agc.reset(m_agcTarget*100.0); // Quench AGC at -20dB the target
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m_squelchDelayLine.write(sideband[i]);
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}
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else
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{
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m_squelchDelayLine.write(sideband[i]*agcVal);
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}
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m_magsqPrev = m_magsqCur;
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if (m_audioMute)
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{
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@ -101,6 +101,8 @@ private:
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double m_magsqSum;
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double m_magsqPeak;
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int m_magsqCount;
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double m_magsqCur;
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double m_magsqPrev;
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MagSqLevelsStore m_magSqLevelStore;
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MagAGC m_agc;
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bool m_agcActive;
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@ -32,6 +32,7 @@ public:
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void setOrder(double R) { m_R = R; }
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Real getValue();
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Real getAverage();
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void reset(double R) { m_moving_average.fill(R); }
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virtual void feed(Complex& ci) = 0;
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protected:
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