SSM modulator: added audio compressor

plugins/channelrx/demodssb/ssbdemod.cpp

@@ -325,6 +325,7 @@ bool SSBDemod::handleMessage(const Message& cmd)
 		if (m_agcNbSamples != agcNbSamples)
 		{
 		    m_agc.resize(agcNbSamples, agcTarget);
+		    m_agc.setStepDownDelay(agcNbSamples);
 		    m_agcNbSamples = agcNbSamples;
 		}
 

plugins/channeltx/modssb/ssbmod.cpp

@@ -24,6 +24,7 @@
 #include <dsp/upchannelizer.h>
 #include "dsp/dspengine.h"
 #include "dsp/pidcontroller.h"
+#include "util/db.h"
 
 MESSAGE_CLASS_DEFINITION(SSBMod::MsgConfigureSSBMod, Message)
 MESSAGE_CLASS_DEFINITION(SSBMod::MsgConfigureFileSourceName, Message)
@@ -45,7 +46,6 @@ SSBMod::SSBMod(BasebandSampleSink* sampleSink) :
 	m_DSBFilterBufferIndex(0),
     m_sampleSink(sampleSink),
     m_movingAverage(40, 0),
-    m_volumeAGC(40, 0),
     m_audioFifo(4, 48000),
 	m_settingsMutex(QMutex::Recursive),
 	m_fileSize(0),
@@ -54,7 +54,8 @@ SSBMod::SSBMod(BasebandSampleSink* sampleSink) :
 	m_afInput(SSBModInputNone),
 	m_levelCalcCount(0),
 	m_peakLevel(0.0f),
-	m_levelSum(0.0f)
+	m_levelSum(0.0f),
+	m_inAGC(9600, 0.2, 1e-4)
 {
 	setObjectName("SSBMod");
 
@@ -84,7 +85,6 @@ SSBMod::SSBMod(BasebandSampleSink* sampleSink) :
     m_sumCount = 0;
 
 	m_movingAverage.resize(16, 0);
-	m_volumeAGC.resize(4096, 0.003, 0);
 	m_magsq = 0.0;
 
 	m_toneNco.setFreq(1000.0, m_config.m_audioSampleRate);
@@ -96,6 +96,9 @@ SSBMod::SSBMod(BasebandSampleSink* sampleSink) :
 	m_cwKeyer.setMode(CWKeyer::CWNone);
 
 	m_cwSmoother.setNbFadeSamples(192); // 4 ms at 48 kHz
+	m_inAGC.setGate(m_config.m_agcThresholdGate);
+	m_inAGC.setStepDownDelay(m_config.m_agcThresholdDelay);
+	m_inAGC.setClamping(true);
     apply();
 }
 
@@ -130,7 +133,12 @@ void SSBMod::configure(MessageQueue* messageQueue,
 		bool audioFlipChannels,
 		bool dsb,
 		bool audioMute,
-		bool playLoop)
+		bool playLoop,
+		bool agc,
+		int agcTime,
+		int agcThreshold,
+		int agcThresholdGate,
+		int agcThresholdDelay)
 {
 	Message* cmd = MsgConfigureSSBMod::create(bandwidth,
 			lowCutoff,
@@ -141,7 +149,12 @@ void SSBMod::configure(MessageQueue* messageQueue,
 			audioFlipChannels,
 			dsb,
 			audioMute,
-			playLoop);
+			playLoop,
+			agc,
+			agcTime,
+			agcThreshold,
+			agcThresholdGate,
+			agcThresholdDelay);
 	messageQueue->push(cmd);
 }
 
@@ -282,11 +295,22 @@ void SSBMod::pullAF(Complex& sample)
             	{
                     Real real;
                 	m_ifstream.read(reinterpret_cast<char*>(&real), sizeof(Real));
+
+                	if (m_running.m_agc)
+                	{
+                        ci.real(real);
+                        ci.imag(0.0f);
+                        m_inAGC.feed(ci);
+                        ci *= m_running.m_volumeFactor;
+                	}
+                	else
+                	{
                         ci.real(real * m_running.m_volumeFactor);
                         ci.imag(0.0f);
                 	}
             	}
             }
+        }
         else
         {
             ci.real(0.0f);
@@ -308,10 +332,20 @@ void SSBMod::pullAF(Complex& sample)
         	}
     	}
         else
+        {
+            if (m_running.m_agc)
+            {
+                ci.real(((m_audioBuffer[m_audioBufferFill].l + m_audioBuffer[m_audioBufferFill].r)  / 65536.0f));
+                ci.imag(0.0f);
+                m_inAGC.feed(ci);
+                ci *= m_running.m_volumeFactor;
+            }
+            else
             {
                 ci.real(((m_audioBuffer[m_audioBufferFill].l + m_audioBuffer[m_audioBufferFill].r)  / 65536.0f) * m_running.m_volumeFactor);
                 ci.imag(0.0f);
             }
+        }
 
         break;
     case SSBModInputCWTone:
@@ -580,6 +614,13 @@ bool SSBMod::handleMessage(const Message& cmd)
 		m_config.m_dsb = cfg.getDSB();
 		m_config.m_audioMute = cfg.getAudioMute();
 		m_config.m_playLoop = cfg.getPlayLoop();
+		m_config.m_agc = cfg.getAGC();
+
+		m_config.m_agcTime = 48 * cfg.getAGCTime(); // ms
+		m_config.m_agcThresholdEnable = cfg.getAGCThreshold() != -99;
+		m_config.m_agcThreshold = CalcDb::powerFromdB(cfg.getAGCThreshold()); // power dB
+		m_config.m_agcThresholdGate = 48 * cfg.getAGCThresholdGate(); // ms
+		m_config.m_agcThresholdDelay = 48 * cfg.getAGCThresholdDelay(); // ms
 
 		apply();
 
@@ -595,7 +636,13 @@ bool SSBMod::handleMessage(const Message& cmd)
 				<< " m_audioFlipChannels: " << m_config.m_audioFlipChannels
 				<< " m_dsb: " << m_config.m_dsb
 				<< " m_audioMute: " << m_config.m_audioMute
-				<< " m_playLoop: " << m_config.m_playLoop;
+				<< " m_playLoop: " << m_config.m_playLoop
+				<< " m_agc: " << m_config.m_agc
+				<< " m_agcTime: " << m_config.m_agcTime
+                << " m_agcThresholdEnable: " << m_config.m_agcThresholdEnable
+                << " m_agcThreshold: " << m_config.m_agcThreshold
+                << " m_agcThresholdGate: " << m_config.m_agcThresholdGate
+                << " m_agcThresholdDelay: " << m_config.m_agcThresholdDelay;
 
 		return true;
 	}
@@ -705,6 +752,31 @@ void SSBMod::apply()
 		}
 	}
 
+    if (m_config.m_agcTime != m_running.m_agcTime)
+    {
+        m_inAGC.resize(m_config.m_agcTime, 0.2);
+    }
+
+    if (m_config.m_agcThresholdEnable != m_running.m_agcThresholdEnable)
+    {
+        m_inAGC.setThresholdEnable(m_config.m_agcThresholdEnable);
+    }
+
+    if (m_config.m_agcThreshold != m_running.m_agcThreshold)
+    {
+        m_inAGC.setThreshold(m_config.m_agcThreshold);
+    }
+
+    if (m_config.m_agcThresholdGate != m_running.m_agcThresholdGate)
+    {
+        m_inAGC.setGate(m_config.m_agcThresholdGate);
+    }
+
+    if (m_config.m_agcThresholdDelay != m_running.m_agcThresholdDelay)
+    {
+        m_inAGC.setStepDownDelay(m_config.m_agcThresholdDelay);
+    }
+
 	m_running.m_outputSampleRate = m_config.m_outputSampleRate;
 	m_running.m_inputFrequencyOffset = m_config.m_inputFrequencyOffset;
 	m_running.m_bandwidth = m_config.m_bandwidth;
@@ -719,6 +791,12 @@ void SSBMod::apply()
 	m_running.m_dsb = m_config.m_dsb;
 	m_running.m_audioMute = m_config.m_audioMute;
 	m_running.m_playLoop = m_config.m_playLoop;
+	m_running.m_agc = m_config.m_agc;
+    m_running.m_agcTime = m_config.m_agcTime;
+    m_running.m_agcThresholdEnable = m_config.m_agcThresholdEnable;
+    m_running.m_agcThreshold = m_config.m_agcThreshold;
+    m_running.m_agcThresholdGate = m_config.m_agcThresholdGate;
+    m_running.m_agcThresholdDelay = m_config.m_agcThresholdDelay;
 }
 
 void SSBMod::openFileStream()

plugins/channeltx/modssb/ssbmod.h

@@ -187,7 +187,12 @@ public:
 			bool audioFlipChannels,
 			bool dsb,
 			bool audioMute,
-            bool playLoop);
+            bool playLoop,
+            bool agc,
+            int agcTime,
+            int agcThreshold,
+            int agcThresholdGate,
+            int agcThresholdDelay);
 
     virtual void pull(Sample& sample);
     virtual void pullAudio(int nbSamples);
@@ -225,6 +230,11 @@ private:
         bool getDSB() const { return m_dsb; }
         bool getAudioMute() const { return m_audioMute; }
         bool getPlayLoop() const { return m_playLoop; }
+        bool getAGC() const { return m_agc; }
+        int getAGCTime() const { return m_agcTime; }
+        int getAGCThreshold() const { return m_agcThreshold; }
+        int getAGCThresholdGate() const { return m_agcThresholdGate; }
+        int getAGCThresholdDelay() const { return m_agcThresholdDelay; }
 
         static MsgConfigureSSBMod* create(Real bandwidth,
         		Real lowCutoff,
@@ -235,7 +245,12 @@ private:
 				bool audioFlipChannels,
 				bool dsb,
 				bool audioMute,
-				bool playLoop)
+				bool playLoop,
+				bool agc,
+				int agcTime,
+                int agcThreshold,
+                int agcThresholdGate,
+                int agcThresholdDelay)
         {
             return new MsgConfigureSSBMod(bandwidth,
             		lowCutoff,
@@ -246,7 +261,12 @@ private:
 					audioFlipChannels,
 					dsb,
 					audioMute,
-					playLoop);
+					playLoop,
+					agc,
+					agcTime,
+					agcThreshold,
+					agcThresholdGate,
+					agcThresholdDelay);
         }
 
     private:
@@ -260,6 +280,11 @@ private:
 		bool m_dsb;
         bool m_audioMute;
         bool m_playLoop;
+        bool m_agc;
+        int m_agcTime;
+        int m_agcThreshold;
+        int m_agcThresholdGate;
+        int m_agcThresholdDelay;
 
         MsgConfigureSSBMod(Real bandwidth,
         		Real lowCutoff,
@@ -270,7 +295,12 @@ private:
 				bool audioFlipChannels,
 				bool dsb,
 				bool audioMute,
-				bool playLoop) :
+				bool playLoop,
+				bool agc,
+				int agcTime,
+				int agcThreshold,
+				int agcThresholdGate,
+				int agcThresholdDelay) :
             Message(),
             m_bandwidth(bandwidth),
 			m_lowCutoff(lowCutoff),
@@ -281,7 +311,12 @@ private:
 			m_audioFlipChannels(audioFlipChannels),
 			m_dsb(dsb),
             m_audioMute(audioMute),
-			m_playLoop(playLoop)
+			m_playLoop(playLoop),
+			m_agc(agc),
+			m_agcTime(agcTime),
+			m_agcThreshold(agcThreshold),
+			m_agcThresholdGate(agcThresholdGate),
+			m_agcThresholdDelay(agcThresholdDelay)
         { }
     };
 
@@ -313,6 +348,12 @@ private:
 		bool m_dsb;
 		bool m_audioMute;
         bool m_playLoop;
+        bool m_agc;
+        int m_agcTime;
+        bool m_agcThresholdEnable;
+        double m_agcThreshold;
+        int m_agcThresholdGate;
+        int m_agcThresholdDelay;
 
         Config() :
             m_outputSampleRate(0),
@@ -328,7 +369,13 @@ private:
 			m_audioFlipChannels(false),
 			m_dsb(false),
             m_audioMute(false),
-			m_playLoop(false)
+			m_playLoop(false),
+			m_agc(false),
+			m_agcTime(9600),
+			m_agcThresholdEnable(true),
+			m_agcThreshold(1e-4),
+			m_agcThresholdGate(192),
+			m_agcThresholdDelay(2400)
         { }
     };
 
@@ -365,7 +412,6 @@ private:
 
     double m_magsq;
     MovingAverage<double> m_movingAverage;
-    SimpleAGC m_volumeAGC;
 
     AudioVector m_audioBuffer;
     uint m_audioBufferFill;
@@ -386,6 +432,8 @@ private:
     CWKeyer m_cwKeyer;
     CWSmoother m_cwSmoother;
 
+    MagAGC m_inAGC;
+
     static const int m_levelNbSamples;
 
     void apply();

plugins/channeltx/modssb/ssbmodgui.cpp

@@ -36,6 +36,18 @@
 
 const QString SSBModGUI::m_channelID = "sdrangel.channeltx.modssb";
 
+const int SSBModGUI::m_agcTimeConstant[] = {
+        1,
+        2,
+        5,
+       10,
+       20,
+       50,
+      100,
+      200,
+      500,
+      990};
+
 SSBModGUI* SSBModGUI::create(PluginAPI* pluginAPI, DeviceSinkAPI *deviceAPI)
 {
     SSBModGUI* gui = new SSBModGUI(pluginAPI, deviceAPI);
@@ -105,6 +117,11 @@ QByteArray SSBModGUI::serialize() const
     s.writeBool(9, ui->audioBinaural->isChecked());
     s.writeBool(10, ui->audioFlipChannels->isChecked());
     s.writeBool(11, ui->dsb->isChecked());
+    s.writeBool(12, ui->agc->isChecked());
+    s.writeS32(13, ui->agcTime->value());
+    s.writeS32(14, ui->agcThreshold->value());
+    s.writeS32(15, ui->agcThresholdGate->value());
+    s.writeS32(16, ui->agcThresholdDelay->value());
 
 	return s.final();
 }
@@ -158,6 +175,18 @@ bool SSBModGUI::deserialize(const QByteArray& data)
         ui->audioFlipChannels->setChecked(booltmp);
         d.readBool(11, &booltmp);
         ui->dsb->setChecked(booltmp);
+        d.readBool(12, &booltmp, false);
+        ui->agc->setChecked(booltmp);
+        d.readS32(13, &tmp, 7);
+        ui->agcTime->setValue(tmp > 9 ? 9 : tmp);
+        d.readS32(14, &tmp, -40);
+        ui->agcThreshold->setValue(tmp);
+        d.readS32(15, &tmp, 4);
+        ui->agcThresholdGate->setValue(tmp);
+        d.readS32(16, &tmp, 5);
+        ui->agcThresholdDelay->setValue(tmp);
+
+        displaySettings();
 
         blockApplySettings(false);
 		m_channelMarker.blockSignals(false);
@@ -399,6 +428,37 @@ void SSBModGUI::on_mic_toggled(bool checked)
     m_ssbMod->getInputMessageQueue()->push(message);
 }
 
+void SSBModGUI::on_agc_stateChanged(int state __attribute((__unused__)))
+{
+    applySettings();
+}
+
+void SSBModGUI::on_agcTime_valueChanged(int value){
+    QString s = QString::number(m_agcTimeConstant[value], 'f', 0);
+    ui->agcTimeText->setText(s);
+    applySettings();
+}
+
+void SSBModGUI::on_agcThreshold_valueChanged(int value)
+{
+    displayAGCPowerThreshold(value);
+    applySettings();
+}
+
+void SSBModGUI::on_agcThresholdGate_valueChanged(int value)
+{
+    QString s = QString::number(value, 'f', 0);
+    ui->agcThresholdGateText->setText(s);
+    applySettings();
+}
+
+void SSBModGUI::on_agcThresholdDelay_valueChanged(int value)
+{
+    QString s = QString::number(value * 10, 'f', 0);
+    ui->agcThresholdDelayText->setText(s);
+    applySettings();
+}
+
 void SSBModGUI::on_navTimeSlider_valueChanged(int value)
 {
     if (m_enableNavTime && ((value >= 0) && (value <= 100)))
@@ -507,6 +567,7 @@ SSBModGUI::SSBModGUI(PluginAPI* pluginAPI, DeviceSinkAPI *deviceAPI, QWidget* pa
     ui->cwKeyerGUI->setBuddies(m_ssbMod->getInputMessageQueue(), m_ssbMod->getCWKeyer());
     ui->spectrumGUI->setBuddies(m_spectrumVis->getInputMessageQueue(), m_spectrumVis, ui->glSpectrum);
 
+    displaySettings();
 	applySettings();
 	setNewRate(m_spanLog2);
 
@@ -629,7 +690,36 @@ void SSBModGUI::applySettings()
 			ui->audioFlipChannels->isChecked(),
 			ui->dsb->isChecked(),
 			ui->audioMute->isChecked(),
-			ui->playLoop->isChecked());
+			ui->playLoop->isChecked(),
+			ui->agc->isChecked(),
+			m_agcTimeConstant[ui->agcTime->value()],
+            ui->agcThreshold->value(),
+            ui->agcThresholdGate->value(),
+            ui->agcThresholdDelay->value() * 10);
+	}
+}
+
+void SSBModGUI::displaySettings()
+{
+    QString s = QString::number(m_agcTimeConstant[ui->agcTime->value()], 'f', 0);
+    ui->agcTimeText->setText(s);
+    displayAGCPowerThreshold(ui->agcThreshold->value());
+    s = QString::number(ui->agcThresholdGate->value(), 'f', 0);
+    ui->agcThresholdGateText->setText(s);
+    s = QString::number(ui->agcThresholdDelay->value() * 10, 'f', 0);
+    ui->agcThresholdDelayText->setText(s);
+}
+
+void SSBModGUI::displayAGCPowerThreshold(int value)
+{
+    if (value == -99)
+    {
+        ui->agcThresholdText->setText("---");
+    }
+    else
+    {
+        QString s = QString::number(value, 'f', 0);
+        ui->agcThresholdText->setText(s);
     }
 }
 

plugins/channeltx/modssb/ssbmodgui.h

@@ -71,6 +71,11 @@ private slots:
     void on_tone_toggled(bool checked);
     void on_toneFrequency_valueChanged(int value);
     void on_mic_toggled(bool checked);
+    void on_agc_stateChanged(int state);
+    void on_agcTime_valueChanged(int value);
+    void on_agcThreshold_valueChanged(int value);
+    void on_agcThresholdGate_valueChanged(int value);
+    void on_agcThresholdDelay_valueChanged(int value);
     void on_play_toggled(bool checked);
     void on_playLoop_toggled(bool checked);
     void on_morseKeyer_toggled(bool checked);
@@ -107,6 +112,7 @@ private:
     std::size_t m_tickCount;
     bool m_enableNavTime;
     SSBMod::SSBModInputAF m_modAFInput;
+    static const int m_agcTimeConstant[]; //!< time constant index to value in ms
 
     explicit SSBModGUI(PluginAPI* pluginAPI, DeviceSinkAPI *deviceAPI, QWidget* parent = NULL);
     virtual ~SSBModGUI();
@@ -116,6 +122,8 @@ private:
 
     void blockApplySettings(bool block);
     void applySettings();
+    void displaySettings();
+    void displayAGCPowerThreshold(int value);
     void updateWithStreamData();
     void updateWithStreamTime();
 

plugins/channeltx/modssb/ssbmodgui.ui

@@ -463,6 +463,204 @@
       </item>
      </layout>
     </item>
+    <item>
+     <layout class="QHBoxLayout" name="horizontalLayout_agc">
+      <item>
+       <widget class="QCheckBox" name="agc">
+        <property name="toolTip">
+         <string>Toggle audio compressor</string>
+        </property>
+        <property name="text">
+         <string>Cmp</string>
+        </property>
+       </widget>
+      </item>
+      <item>
+       <widget class="QDial" name="agcTime">
+        <property name="maximumSize">
+         <size>
+          <width>24</width>
+          <height>24</height>
+         </size>
+        </property>
+        <property name="toolTip">
+         <string>Compressor time constant (attack)</string>
+        </property>
+        <property name="minimum">
+         <number>0</number>
+        </property>
+        <property name="maximum">
+         <number>9</number>
+        </property>
+        <property name="pageStep">
+         <number>1</number>
+        </property>
+        <property name="value">
+         <number>4</number>
+        </property>
+       </widget>
+      </item>
+      <item>
+       <widget class="QLabel" name="agcTimeText">
+        <property name="minimumSize">
+         <size>
+          <width>25</width>
+          <height>0</height>
+         </size>
+        </property>
+        <property name="toolTip">
+         <string>Compressor time constant in ms</string>
+        </property>
+        <property name="text">
+         <string>000</string>
+        </property>
+        <property name="alignment">
+         <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+        </property>
+       </widget>
+      </item>
+      <item>
+       <widget class="QDial" name="agcThreshold">
+        <property name="maximumSize">
+         <size>
+          <width>24</width>
+          <height>24</height>
+         </size>
+        </property>
+        <property name="toolTip">
+         <string>Audio squelch threshold</string>
+        </property>
+        <property name="minimum">
+         <number>-99</number>
+        </property>
+        <property name="maximum">
+         <number>0</number>
+        </property>
+        <property name="pageStep">
+         <number>1</number>
+        </property>
+        <property name="value">
+         <number>-40</number>
+        </property>
+       </widget>
+      </item>
+      <item>
+       <widget class="QLabel" name="agcThresholdText">
+        <property name="minimumSize">
+         <size>
+          <width>14</width>
+          <height>0</height>
+         </size>
+        </property>
+        <property name="toolTip">
+         <string>Audio squelch threshold (dB power)</string>
+        </property>
+        <property name="text">
+         <string>-00</string>
+        </property>
+        <property name="alignment">
+         <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+        </property>
+       </widget>
+      </item>
+      <item>
+       <widget class="QDial" name="agcThresholdGate">
+        <property name="maximumSize">
+         <size>
+          <width>24</width>
+          <height>24</height>
+         </size>
+        </property>
+        <property name="toolTip">
+         <string>Audio squelch gate</string>
+        </property>
+        <property name="pageStep">
+         <number>1</number>
+        </property>
+        <property name="value">
+         <number>4</number>
+        </property>
+       </widget>
+      </item>
+      <item>
+       <widget class="QLabel" name="agcThresholdGateText">
+        <property name="minimumSize">
+         <size>
+          <width>18</width>
+          <height>0</height>
+         </size>
+        </property>
+        <property name="toolTip">
+         <string>Audio squelch gate in ms</string>
+        </property>
+        <property name="text">
+         <string>00</string>
+        </property>
+        <property name="alignment">
+         <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+        </property>
+       </widget>
+      </item>
+      <item>
+       <widget class="QDial" name="agcThresholdDelay">
+        <property name="maximumSize">
+         <size>
+          <width>24</width>
+          <height>24</height>
+         </size>
+        </property>
+        <property name="toolTip">
+         <string>Audio squelch delay (release)</string>
+        </property>
+        <property name="pageStep">
+         <number>1</number>
+        </property>
+        <property name="value">
+         <number>5</number>
+        </property>
+       </widget>
+      </item>
+      <item>
+       <widget class="QLabel" name="agcThresholdDelayText">
+        <property name="minimumSize">
+         <size>
+          <width>25</width>
+          <height>0</height>
+         </size>
+        </property>
+        <property name="toolTip">
+         <string>Audio squelch delay in ms</string>
+        </property>
+        <property name="text">
+         <string>000</string>
+        </property>
+        <property name="alignment">
+         <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+        </property>
+       </widget>
+      </item>
+      <item>
+       <spacer name="horizontalSpacer">
+        <property name="orientation">
+         <enum>Qt::Horizontal</enum>
+        </property>
+        <property name="sizeHint" stdset="0">
+         <size>
+          <width>40</width>
+          <height>20</height>
+         </size>
+        </property>
+       </spacer>
+      </item>
+     </layout>
+    </item>
+    <item>
+     <widget class="Line" name="line">
+      <property name="orientation">
+       <enum>Qt::Horizontal</enum>
+      </property>
+     </widget>
+    </item>
     <item>
      <layout class="QHBoxLayout" name="inputSelectLayout">
       <item>

sdrbase/dsp/agc.cpp

@@ -53,7 +53,11 @@ MagAGC::MagAGC(int historySize, double R, double threshold) :
     m_stepDelta(1.0/m_stepLength),
 	m_stepUpCounter(0),
     m_stepDownCounter(m_stepLength),
-	m_gateCounter(0)
+	m_gateCounter(0),
+	m_stepDownDelay(historySize),
+	m_clamping(false),
+	m_R2(R*R),
+	m_clampMax(1.0)
 {}
 
 MagAGC::~MagAGC()
@@ -61,6 +65,7 @@ MagAGC::~MagAGC()
 
 void MagAGC::resize(int historySize, Real R)
 {
+    m_R2 = R*R;
     m_stepLength = std::min(StepLengthMax, historySize/2);
     m_stepDelta = 1.0 / m_stepLength;
     m_stepUpCounter = 0;
@@ -88,7 +93,24 @@ double MagAGC::feedAndGetValue(const Complex& ci)
 {
     m_magsq = ci.real()*ci.real() + ci.imag()*ci.imag();
     m_moving_average.feed(m_magsq);
+
+    if (m_clamping)
+    {
+        if (m_squared)
+        {
+            double u0 = m_R / m_moving_average.average();
+            m_u0 = (u0 * m_magsq > m_clampMax) ? m_clampMax / m_magsq : u0;
+        }
+        else
+        {
+            double u02 = m_R2 / m_moving_average.average();
+            m_u0 = (u02 * m_magsq > m_clampMax) ? m_clampMax / sqrt(m_magsq) : sqrt(u02);
+        }
+    }
+    else
+    {
         m_u0 = m_R / (m_squared ? m_moving_average.average() : sqrt(m_moving_average.average()));
+    }
 
     if (m_thresholdEnable)
     {
@@ -105,14 +127,14 @@ double MagAGC::feedAndGetValue(const Complex& ci)
         }
         else
         {
-            if (m_count < m_moving_average.historySize()) {
+            if (m_count < m_stepDownDelay) {
                 m_count++;
             }
 
             m_gateCounter = 0;
         }
 
-        if (m_count <  m_moving_average.historySize())
+        if (m_count <  m_stepDownDelay)
         {
             m_stepDownCounter = m_stepUpCounter;
 

sdrbase/dsp/agc.h

@@ -22,11 +22,11 @@ public:
 	virtual void feed(Complex& ci) = 0;
 
 protected:
-	double m_u0;
+	double m_u0;                            //!< AGC factor
-	double m_R;       // objective mag
+	double m_R;                             //!< objective mag
-	MovingAverage<double> m_moving_average; // Averaging engine. The stack length conditions the smoothness of AGC.
+	MovingAverage<double> m_moving_average; //!< Averaging engine. The stack length conditions the smoothness of AGC.
-	int m_historySize;
+	int m_historySize;                      //!< Averaging length (attack)
-	int m_count;
+	int m_count;                            //!< Samples counter
 };
 
 
@@ -43,6 +43,9 @@ public:
     void setThreshold(double threshold) { m_threshold = threshold; }
     void setThresholdEnable(bool enable);
     void setGate(int gate) { m_gate = gate; }
+    void setStepDownDelay(int stepDownDelay) { m_stepDownDelay = stepDownDelay; }
+    void setClamping(bool clamping) { m_clamping = clamping; }
+    void setClampMax(double clampMax) { m_clampMax = clampMax; }
 private:
     bool m_squared;        //!< use squared magnitude (power) to compute AGC value
 	double m_magsq;        //!< current squared magnitude (power)
@@ -54,6 +57,10 @@ private:
     int m_stepUpCounter;   //!< step up transition samples counter
     int m_stepDownCounter; //!< step down transition samples counter
     int m_gateCounter;     //!< threshold gate samples counter
+    int m_stepDownDelay;   //!< delay in samples before cutoff (release)
+    bool m_clamping;       //!< clamping active
+    double m_R2;           //!< square of objective magnitude
+    double m_clampMax;     //!< maximum to clamp to
 };