SSB demod: updated AGC

plugins/channelrx/demodssb/ssbdemod.cpp

@@ -24,6 +24,7 @@
 #include <stdio.h>
 #include "audio/audiooutput.h"
 #include "dsp/dspengine.h"
+#include "util/db.h"
 
 MESSAGE_CLASS_DEFINITION(SSBDemod::MsgConfigureSSBDemod, Message)
 
@@ -32,7 +33,10 @@ SSBDemod::SSBDemod(BasebandSampleSink* sampleSink) :
 	m_audioFlipChannels(false),
     m_dsb(false),
     m_audioMute(false),
-    m_agc(12000, 40.0, 1e-2),
+    m_agc(12000, agcTarget, 1e-2),
+    m_agcActive(false),
+    m_agcNbSamples(12000),
+    m_agcPowerThreshold(1e-2),
     m_sampleSink(sampleSink),
     m_audioFifo(4, 24000),
     m_settingsMutex(QMutex::Recursive)
@@ -181,25 +185,25 @@ void SSBDemod::feed(const SampleVector::const_iterator& begin, const SampleVecto
 			}
 			else
 			{
-			    double agcVal = m_agc.feedAndGetValue(sideband[i]);
+			    double agcVal = m_agcActive ? m_agc.feedAndGetValue(sideband[i]) : 1.0;
 
 				if (m_audioBinaual)
 				{
 					if (m_audioFlipChannels)
 					{
-						m_audioBuffer[m_audioBufferFill].r = (qint16)(sideband[i].imag() * m_volume * agcVal * 10);
+						m_audioBuffer[m_audioBufferFill].r = (qint16)(sideband[i].imag() * m_volume * agcVal);
-						m_audioBuffer[m_audioBufferFill].l = (qint16)(sideband[i].real() * m_volume * agcVal * 10);
+						m_audioBuffer[m_audioBufferFill].l = (qint16)(sideband[i].real() * m_volume * agcVal);
 					}
 					else
 					{
-						m_audioBuffer[m_audioBufferFill].r = (qint16)(sideband[i].real() * m_volume * agcVal * 10);
+						m_audioBuffer[m_audioBufferFill].r = (qint16)(sideband[i].real() * m_volume * agcVal);
-						m_audioBuffer[m_audioBufferFill].l = (qint16)(sideband[i].imag() * m_volume * agcVal * 10);
+						m_audioBuffer[m_audioBufferFill].l = (qint16)(sideband[i].imag() * m_volume * agcVal);
 					}
 				}
 				else
 				{
 					Real demod = (sideband[i].real() + sideband[i].imag()) * 0.7;
-					qint16 sample = (qint16)(demod * m_volume * agcVal * 10);
+					qint16 sample = (qint16)(demod * m_volume * agcVal);
 					m_audioBuffer[m_audioBufferFill].l = sample;
 					m_audioBuffer[m_audioBufferFill].r = sample;
 				}
@@ -305,6 +309,22 @@ bool SSBDemod::handleMessage(const Message& cmd)
 		m_audioFlipChannels = cfg.getAudioFlipChannels();
 		m_dsb = cfg.getDSB();
 		m_audioMute = cfg.getAudioMute();
+		m_agcActive = cfg.getAGC();
+
+		int agcNbSamples = 48 * (1<<cfg.getAGCTimeLog2());
+		double agcPowerThreshold = CalcDb::powerFromdB(cfg.getAGCPowerThershold()) * (1<<30);
+
+		if (m_agcNbSamples != agcNbSamples)
+		{
+		    m_agc.resize(agcNbSamples, agcTarget);
+		    m_agcNbSamples = agcNbSamples;
+		}
+
+		if (m_agcPowerThreshold != agcPowerThreshold)
+		{
+		    m_agc.setThreshold(agcPowerThreshold);
+		    m_agcPowerThreshold = agcPowerThreshold;
+		}
 
 		m_settingsMutex.unlock();
 
@@ -315,7 +335,10 @@ bool SSBDemod::handleMessage(const Message& cmd)
 				<< " m_audioBinaual: " << m_audioBinaual
 				<< " m_audioFlipChannels: " << m_audioFlipChannels
 				<< " m_dsb: " << m_dsb
-				<< "m_audioMute: " << m_audioMute;
+				<< " m_audioMute: " << m_audioMute
+				<< " m_agcActive: " << m_agcActive
+				<< " agcNbSamples: " << agcNbSamples
+				<< " agcPowerThreshold: " << agcPowerThreshold;
 
 		return true;
 	}

plugins/channelrx/demodssb/ssbdemod.h

@@ -29,6 +29,7 @@
 #include "util/message.h"
 
 #define ssbFftLen 1024
+#define agcTarget 327.68 // -20 dB amplitude => -40 dB power: center of normal signal
 
 class SSBDemod : public BasebandSampleSink {
 public:
@@ -173,6 +174,9 @@ private:
 	double m_magsqPeak;
     int  m_magsqCount;
     MagAGC m_agc;
+    bool m_agcActive;
+    int m_agcNbSamples;         //!< number of audio (48 kHz) samples for AGC averaging
+    double m_agcPowerThreshold; //!< AGC power threshold (linear)
 
 	NCOF m_nco;
 	Interpolator m_interpolator;

plugins/channelrx/demodssb/ssbdemodgui.cpp

@@ -79,6 +79,9 @@ QByteArray SSBDemodGUI::serialize() const
 	s.writeBool(8, m_audioBinaural);
 	s.writeBool(9, m_audioFlipChannels);
 	s.writeBool(10, m_dsb);
+	s.writeBool(11, ui->agc->isChecked());
+	s.writeS32(12, ui->agcTimeLog2->value());
+	s.writeS32(13, ui->agcPowerThreshold->value());
 	return s.final();
 }
 
@@ -97,6 +100,7 @@ bool SSBDemodGUI::deserialize(const QByteArray& data)
 		QByteArray bytetmp;
 		quint32 u32tmp;
 		qint32 tmp;
+		bool booltmp;
 
 		blockApplySettings(true);
 	    m_channelMarker.blockSignals(true);
@@ -122,6 +126,12 @@ bool SSBDemodGUI::deserialize(const QByteArray& data)
 		ui->audioFlipChannels->setChecked(m_audioFlipChannels);
 		d.readBool(10, &m_dsb);
 		ui->dsb->setChecked(m_dsb);
+		d.readBool(11, &booltmp, false);
+		ui->agc->setChecked(booltmp);
+		d.readS32(12, &tmp, 7);
+		ui->agcTimeText->setText(QString("%1").arg((1<<tmp), 0, 'f', 0));
+        d.readS32(13, &tmp, -20);
+        ui->agcPowerThresholdText->setText(QString("%1").arg(tmp, 0, 'f', 0));
 
 		blockApplySettings(false);
 	    m_channelMarker.blockSignals(false);
@@ -265,6 +275,23 @@ void SSBDemodGUI::on_volume_valueChanged(int value)
 	applySettings();
 }
 
+void SSBDemodGUI::on_agc_stateChanged(int state)
+{
+    applySettings();
+}
+
+void SSBDemodGUI::on_agcTimeLog2_valueChanged(int value)
+{
+    ui->agcTimeText->setText(QString("%1").arg((1<<value), 0, 'f', 0));
+    applySettings();
+}
+
+void SSBDemodGUI::on_agcPowerThreshold_valueChanged(int value)
+{
+    ui->agcPowerThresholdText->setText(QString("%1").arg(value, 0, 'f', 0));
+    applySettings();
+}
+
 void SSBDemodGUI::on_audioMute_toggled(bool checked)
 {
 	m_audioMute = checked;

plugins/channelrx/demodssb/ssbdemodgui.ui

@@ -433,6 +433,9 @@
           <height>24</height>
          </size>
         </property>
+        <property name="pageStep">
+         <number>1</number>
+        </property>
        </widget>
       </item>
       <item>
@@ -489,6 +492,12 @@
       </item>
       <item>
        <widget class="QLabel" name="agcTimeText">
+        <property name="minimumSize">
+         <size>
+          <width>30</width>
+          <height>0</height>
+         </size>
+        </property>
         <property name="toolTip">
          <string>AGC time constant (ms)</string>
         </property>
@@ -521,12 +530,18 @@
          <number>1</number>
         </property>
         <property name="value">
-         <number>-40</number>
+         <number>-50</number>
         </property>
        </widget>
       </item>
       <item>
-       <widget class="QLabel" name="agcPowerThersholdText">
+       <widget class="QLabel" name="agcPowerThresholdText">
+        <property name="minimumSize">
+         <size>
+          <width>20</width>
+          <height>0</height>
+         </size>
+        </property>
         <property name="toolTip">
          <string>AGC power threshold (dB)</string>
         </property>
@@ -677,6 +692,14 @@
   <include location="../../../sdrbase/resources/res.qrc"/>
   <include location="../../../sdrbase/resources/res.qrc"/>
   <include location="../../../sdrbase/resources/res.qrc"/>
+  <include location="../../../sdrbase/resources/res.qrc"/>
+  <include location="../../../sdrbase/resources/res.qrc"/>
+  <include location="../../../sdrbase/resources/res.qrc"/>
+  <include location="../../../sdrbase/resources/res.qrc"/>
+  <include location="../../../sdrbase/resources/res.qrc"/>
+  <include location="../../../sdrbase/resources/res.qrc"/>
+  <include location="../../../sdrbase/resources/res.qrc"/>
+  <include location="../../../sdrbase/resources/res.qrc"/>
  </resources>
  <connections/>
 </ui>

sdrbase/dsp/agc.cpp

@@ -45,7 +45,8 @@ Real AGC::getAverage()
 MagSquaredAGC::MagSquaredAGC(int historySize, double R, double threshold) :
 	AGC(historySize, R),
 	m_magsq(0.0),
-	m_threshold(threshold)
+	m_threshold(threshold),
+	m_thresholdCount(0)
 {}
 
 MagSquaredAGC::~MagSquaredAGC()
@@ -64,7 +65,19 @@ double MagSquaredAGC::feedAndGetValue(const Complex& ci)
     m_magsq = ci.real()*ci.real() + ci.imag()*ci.imag();
     m_moving_average.feed(m_magsq);
     m_u0 = m_R / m_moving_average.average();
-    return m_magsq > m_threshold ? m_u0 : 1.0;
+
+    if (m_magsq > m_threshold)
+    {
+        m_thresholdCount = 0;
+    }
+    else
+    {
+        if (m_thresholdCount < m_moving_average.historySize()) {
+            m_thresholdCount++;
+        }
+    }
+
+    return (m_thresholdCount <  m_moving_average.historySize()) ? m_u0 : 0.0;
 }
 
 //MagAGC::MagAGC() :
@@ -75,7 +88,8 @@ double MagSquaredAGC::feedAndGetValue(const Complex& ci)
 MagAGC::MagAGC(int historySize, double R, double threshold) :
 	AGC(historySize, R),
 	m_magsq(0.0),
-	m_threshold(threshold)
+	m_threshold(threshold),
+	m_thresholdCount(0)
 {}
 
 MagAGC::~MagAGC()
@@ -94,7 +108,19 @@ double MagAGC::feedAndGetValue(const Complex& ci)
     m_magsq = ci.real()*ci.real() + ci.imag()*ci.imag();
     m_moving_average.feed(m_magsq);
     m_u0 = m_R / sqrt(m_moving_average.average());
-    return m_magsq > m_threshold ? m_u0 : 1.0;
+
+    if (m_magsq > m_threshold)
+    {
+        m_thresholdCount = 0;
+    }
+    else
+    {
+        if (m_thresholdCount < m_moving_average.historySize()) {
+            m_thresholdCount++;
+        }
+    }
+
+    return (m_thresholdCount <  m_moving_average.historySize()) ? m_u0 : 0.0;
 }
 
 //AlphaAGC::AlphaAGC() :

sdrbase/dsp/agc.h

@@ -37,9 +37,11 @@ public:
 	virtual void feed(Complex& ci);
 	double feedAndGetValue(const Complex& ci);
 	double getMagSq() const { return m_magsq; }
+	void setThreshold(double threshold) { m_threshold = threshold; }
 private:
 	double m_magsq;
-	double m_threshold;
+	double m_threshold; //!< squelch on magsq average with transition from +3dB
+    int m_thresholdCount;
 };
 
 class MagAGC : public AGC
@@ -50,9 +52,11 @@ public:
 	virtual void feed(Complex& ci);
     double feedAndGetValue(const Complex& ci);
 	Real getMagSq() const { return m_magsq; }
+    void setThreshold(double threshold) { m_threshold = threshold; }
 private:
 	double m_magsq;
-    double m_threshold;
+    double m_threshold; //!< squelch on magsq average
+    int m_thresholdCount;
 };
 
 class AlphaAGC : public AGC

sdrbase/dsp/movingaverage.h

@@ -50,6 +50,11 @@ public:
 		return m_sum;
 	}
 
+	int historySize() const
+	{
+	    return m_history.size();
+	}
+
 protected:
 	std::vector<Type> m_history;
 	Type m_sum;

sdrbase/util/db.cpp

@@ -28,3 +28,8 @@ double CalcDb::dbPower(double magsq, double floordB)
 		return floordB;
 	}
 }
+
+double CalcDb::powerFromdB(double powerdB)
+{
+    return pow(10.0, powerdB / 10.0);
+}

sdrbase/util/db.h

@@ -23,6 +23,7 @@ class CalcDb
 {
 public:
 	static double dbPower(double magsq, double floordB = -100.0);
+	static double powerFromdB(double powerdB);
 };
 
 #endif /* INCLUDE_UTIL_DB_H_ */