BFM demod: introducing LSB stereo for what it's worth...

include/dsp/phaselock.h

@@ -128,7 +128,9 @@ protected:
     	samples_out[0] = m_psin; // f Pilot
         // Generate double-frequency output.
         // sin(2*x) = 2 * sin(x) * cos(x)
-    	samples_out[1] = 2.0 * m_psin * m_pcos; // 2f Pilot
+    	samples_out[1] = 2.0 * m_psin * m_pcos; // 2f Pilot sin
+        // cos(2*x) = 2 * cos(x) * cos(x) - 1
+    	samples_out[1] = (2.0 * m_pcos * m_pcos) - 1.0; // 2f Pilot cos
     }
 };
 
@@ -150,6 +152,8 @@ protected:
         // Generate double-frequency output.
         // sin(2*x) = 2 * sin(x) * cos(x)
         samples_out[1] = 2.0 * m_psin * m_pcos; // Pilot signal (2f)
-        samples_out[2] = m_phase; // Pilot phase
+        // cos(2*x) = 2 * cos(x) * cos(x) - 1
+    	samples_out[1] = (2.0 * m_pcos * m_pcos) - 1.0; // 2f Pilot cos
+        samples_out[3] = m_phase; // Pilot phase
     }
 };

plugins/channel/bfm/bfmdemod.cpp

@@ -50,7 +50,7 @@ BFMDemod::BFMDemod(SampleSink* sampleSink, RDSParser *rdsParser) :
 	m_config.m_audioSampleRate = DSPEngine::instance()->getAudioSampleRate(); // normally 48 kHz
 	m_deemphasisFilterX.configure(default_deemphasis * m_config.m_audioSampleRate * 1.0e-6);
 	m_deemphasisFilterY.configure(default_deemphasis * m_config.m_audioSampleRate * 1.0e-6);
-	m_rfFilter = new fftfilt(-50000.0 / 384000.0, 50000.0 / 384000.0, rfFilterFftLength);
+	m_rfFilter = new fftfilt(-50000.0 / 384000.0, 50000.0 / 384000.0, filtFftLen);
 	m_phaseDiscri.setFMScaling(384000/m_fmExcursion);
 
 	apply();
@@ -79,6 +79,7 @@ void BFMDemod::configure(MessageQueue* messageQueue,
 		Real volume,
 		Real squelch,
 		bool audioStereo,
+		bool lsbStereo,
 		bool showPilot,
 		bool rdsActive)
 {
@@ -87,6 +88,7 @@ void BFMDemod::configure(MessageQueue* messageQueue,
 			volume,
 			squelch,
 			audioStereo,
+			lsbStereo,
 			showPilot,
 			rdsActive);
 	messageQueue->push(cmd);
@@ -138,8 +140,8 @@ void BFMDemod::feed(const SampleVector::const_iterator& begin, const SampleVecto
 
 			if (m_running.m_rdsActive)
 			{
-				//Complex r(demod * 2.0 * std::cos(3.0 * m_pilotPLLSamples[2]), 0.0);
+				//Complex r(demod * 2.0 * std::cos(3.0 * m_pilotPLLSamples[3]), 0.0);
-				Complex r(demod * 2.0 * std::cos(3.0 * m_pilotPLLSamples[2]), 0.0);
+				Complex r(demod * 2.0 * std::cos(3.0 * m_pilotPLLSamples[3]), 0.0);
 
 				if (m_interpolatorRDS.interpolate(&m_interpolatorRDSDistanceRemain, r, &cr))
 				{
@@ -173,12 +175,26 @@ void BFMDemod::feed(const SampleVector::const_iterator& begin, const SampleVecto
 					m_sampleBuffer.push_back(Sample(m_pilotPLLSamples[1] * (1<<15), 0.0)); // debug 38 kHz pilot
 				}
 
-				Complex s(demod * 1.17 * m_pilotPLLSamples[1], 0);
+				if (m_running.m_lsbStereo)
-
-				if (m_interpolatorStereo.interpolate(&m_interpolatorStereoDistanceRemain, s, &cs))
 				{
-					sampleStereo = cs.real();
+					// 1.17 * 0.7 = 0.819
-					m_interpolatorStereoDistanceRemain += m_interpolatorStereoDistance;
+					Complex s(demod * m_pilotPLLSamples[1], demod * m_pilotPLLSamples[2]);
+
+					if (m_interpolatorStereo.interpolate(&m_interpolatorStereoDistanceRemain, s, &cs))
+					{
+						sampleStereo = cs.real() + cs.imag();
+						m_interpolatorStereoDistanceRemain += m_interpolatorStereoDistance;
+					}
+				}
+				else
+				{
+					Complex s(demod * 1.17 * m_pilotPLLSamples[1], 0);
+
+					if (m_interpolatorStereo.interpolate(&m_interpolatorStereoDistanceRemain, s, &cs))
+					{
+						sampleStereo = cs.real();
+						m_interpolatorStereoDistanceRemain += m_interpolatorStereoDistance;
+					}
 				}
 			}
 
@@ -191,8 +207,16 @@ void BFMDemod::feed(const SampleVector::const_iterator& begin, const SampleVecto
 					Real deemph_l, deemph_r; // Pre-emphasis is applied on each channel before multiplexing
 					m_deemphasisFilterX.process(ci.real() + sampleStereo, deemph_l);
 					m_deemphasisFilterY.process(ci.real() - sampleStereo, deemph_r);
-					m_audioBuffer[m_audioBufferFill].l = (qint16)(deemph_l * (1<<12) * m_running.m_volume);
+					if (m_running.m_lsbStereo)
-					m_audioBuffer[m_audioBufferFill].r = (qint16)(deemph_r * (1<<12) * m_running.m_volume);
+					{
+						m_audioBuffer[m_audioBufferFill].l = (qint16)(deemph_l * (1<<12) * m_running.m_volume * 0.9);
+						m_audioBuffer[m_audioBufferFill].r = (qint16)(deemph_r * (1<<12) * m_running.m_volume * 1.11);
+					}
+					else
+					{
+						m_audioBuffer[m_audioBufferFill].l = (qint16)(deemph_l * (1<<12) * m_running.m_volume);
+						m_audioBuffer[m_audioBufferFill].r = (qint16)(deemph_r * (1<<12) * m_running.m_volume);
+					}
 				}
 				else
 				{
@@ -280,6 +304,7 @@ bool BFMDemod::handleMessage(const Message& cmd)
 		m_config.m_volume = cfg.getVolume();
 		m_config.m_squelch = cfg.getSquelch();
 		m_config.m_audioStereo = cfg.getAudioStereo();
+		m_config.m_lsbStereo = cfg.getLsbStereo();
 		m_config.m_showPilot = cfg.getShowPilot();
 		m_config.m_rdsActive = cfg.getRDSActive();
 
@@ -290,6 +315,7 @@ bool BFMDemod::handleMessage(const Message& cmd)
 				<< " m_volume: " << m_config.m_volume
 				<< " m_squelch: " << m_config.m_squelch
 				<< " m_audioStereo: " << m_config.m_audioStereo
+				<< " m_lsbStereo: " << m_config.m_lsbStereo
 				<< " m_showPilot: " << m_config.m_showPilot
 				<< " m_rdsActive: " << m_config.m_rdsActive;
 
@@ -392,6 +418,7 @@ void BFMDemod::apply()
 	m_running.m_volume = m_config.m_volume;
 	m_running.m_audioSampleRate = m_config.m_audioSampleRate;
 	m_running.m_audioStereo = m_config.m_audioStereo;
+	m_running.m_lsbStereo = m_config.m_lsbStereo;
 	m_running.m_showPilot = m_config.m_showPilot;
 	m_running.m_rdsActive = m_config.m_rdsActive;
 }

plugins/channel/bfm/bfmdemod.h

@@ -34,8 +34,6 @@
 #include "rdsdemod.h"
 #include "rdsdecoder.h"
 
-#define rfFilterFftLength 1024
-
 class RDSParser;
 
 class BFMDemod : public SampleSink {
@@ -49,6 +47,7 @@ public:
 			Real volume,
 			Real squelch,
 			bool audioStereo,
+			bool lsbStereo,
 			bool showPilot,
 			bool rdsActive);
 
@@ -79,6 +78,7 @@ private:
 		Real getVolume() const { return m_volume; }
 		Real getSquelch() const { return m_squelch; }
 		bool getAudioStereo() const { return m_audioStereo; }
+		bool getLsbStereo() const { return m_lsbStereo; }
 		bool getShowPilot() const { return m_showPilot; }
 		bool getRDSActive() const { return m_rdsActive; }
 
@@ -87,6 +87,7 @@ private:
 				Real volume,
 				Real squelch,
 				bool audioStereo,
+				bool lsbStereo,
 				bool showPilot,
 				bool rdsActive)
 		{
@@ -95,6 +96,7 @@ private:
 					volume,
 					squelch,
 					audioStereo,
+					lsbStereo,
 					showPilot,
 					rdsActive);
 		}
@@ -105,6 +107,7 @@ private:
 		Real m_volume;
 		Real m_squelch;
 		bool m_audioStereo;
+		bool m_lsbStereo;
 		bool m_showPilot;
 		bool m_rdsActive;
 
@@ -113,6 +116,7 @@ private:
 				Real volume,
 				Real squelch,
 				bool audioStereo,
+				bool lsbStereo,
 				bool showPilot,
 				bool rdsActive) :
 			Message(),
@@ -121,6 +125,7 @@ private:
 			m_volume(volume),
 			m_squelch(squelch),
 			m_audioStereo(audioStereo),
+			m_lsbStereo(lsbStereo),
 			m_showPilot(showPilot),
 			m_rdsActive(rdsActive)
 		{ }
@@ -146,6 +151,7 @@ private:
 		Real m_volume;
 		quint32 m_audioSampleRate;
 		bool m_audioStereo;
+		bool m_lsbStereo;
 		bool m_showPilot;
 		bool m_rdsActive;
 
@@ -158,6 +164,7 @@ private:
 			m_volume(0),
 			m_audioSampleRate(0),
 			m_audioStereo(false),
+			m_lsbStereo(false),
 			m_showPilot(false),
 			m_rdsActive(false)
 		{ }
@@ -181,6 +188,7 @@ private:
 
 	Lowpass<Real> m_lowpass;
 	fftfilt* m_rfFilter;
+	static const int filtFftLen = 1024;
 
 	Real m_squelchLevel;
 	int m_squelchState;
@@ -198,7 +206,7 @@ private:
 	QMutex m_settingsMutex;
 
 	RDSPhaseLock m_pilotPLL;
-	Real m_pilotPLLSamples[3];
+	Real m_pilotPLLSamples[4];
 
 	RDSDemod m_rdsDemod;
 	RDSDecoder m_rdsDecoder;

plugins/channel/bfm/bfmdemodgui.cpp

@@ -110,6 +110,7 @@ QByteArray BFMDemodGUI::serialize() const
 	s.writeU32(7, m_channelMarker.getColor().rgb());
 	s.writeBlob(8, ui->spectrumGUI->serialize());
 	s.writeBool(9, ui->audioStereo->isChecked());
+	s.writeBool(10, ui->lsbStereo->isChecked());
 	return s.final();
 }
 
@@ -162,6 +163,9 @@ bool BFMDemodGUI::deserialize(const QByteArray& data)
 		d.readBool(9, &booltmp, false);
 		ui->audioStereo->setChecked(booltmp);
 
+		d.readBool(10, &booltmp, false);
+		ui->lsbStereo->setChecked(booltmp);
+
 		blockApplySettings(false);
 	    m_channelMarker.blockSignals(false);
 
@@ -243,6 +247,11 @@ void BFMDemodGUI::on_audioStereo_toggled(bool stereo)
 	applySettings();
 }
 
+void BFMDemodGUI::on_lsbStereo_toggled(bool lsb)
+{
+	applySettings();
+}
+
 void BFMDemodGUI::on_showPilot_clicked()
 {
 	applySettings();
@@ -436,6 +445,7 @@ void BFMDemodGUI::applySettings()
 			ui->volume->value() / 10.0,
 			ui->squelch->value(),
 			ui->audioStereo->isChecked(),
+			ui->lsbStereo->isChecked(),
 			ui->showPilot->isChecked(),
 			ui->rds->isChecked());
 	}

plugins/channel/bfm/bfmdemodgui.h

@@ -63,6 +63,7 @@ private slots:
 	void on_volume_valueChanged(int value);
 	void on_squelch_valueChanged(int value);
 	void on_audioStereo_toggled(bool stereo);
+	void on_lsbStereo_toggled(bool lsb);
 	void on_showPilot_clicked();
 	void on_rds_clicked();
 	void on_g14ProgServiceNames_currentIndexChanged(int index);

plugins/channel/bfm/bfmdemodgui.ui

@@ -21,7 +21,7 @@
     <rect>
      <x>10</x>
      <y>20</y>
-     <width>311</width>
+     <width>411</width>
      <height>121</height>
     </rect>
    </property>
@@ -160,6 +160,26 @@
           </property>
          </widget>
         </item>
+        <item>
+         <widget class="ButtonSwitch" name="lsbStereo">
+          <property name="toolTip">
+           <string>Use only LSB from stereo subcarrier </string>
+          </property>
+          <property name="text">
+           <string/>
+          </property>
+          <property name="icon">
+           <iconset resource="../../../sdrbase/resources/res.qrc">
+            <normaloff>:/lsb.png</normaloff>:/lsb.png</iconset>
+          </property>
+          <property name="checkable">
+           <bool>true</bool>
+          </property>
+          <property name="autoRaise">
+           <bool>true</bool>
+          </property>
+         </widget>
+        </item>
         <item>
          <widget class="ButtonSwitch" name="showPilot">
           <property name="toolTip">

sdrbase/resources/res.qrc

@@ -48,5 +48,6 @@
         <file>carrier.png</file>
         <file>rds.png</file>
         <file>recycle.png</file>
+        <file>lsb.png</file>
     </qresource>
 </RCC>