Audio output device recording: implemented mono recording option

sdrbase/audio/audiooutputdevice.cpp

@@ -218,6 +218,15 @@ void AudioOutputDevice::setUdpChannelFormat(UDPChannelCodec udpChannelCodec, boo
     if (m_audioNetSink) {
         m_audioNetSink->setParameters((AudioNetSink::Codec) m_udpChannelCodec, stereo, sampleRate);
     }
+
+    if (m_wavFileRecord)
+    {
+        if (m_wavFileRecord->isRecording()) {
+            m_wavFileRecord->stopRecording();
+        }
+
+        m_wavFileRecord->setMono(!stereo);
+    }
 }
 
 void AudioOutputDevice::setUdpDecimation(uint32_t decimation)
@@ -403,12 +412,12 @@ qint64 AudioOutputDevice::readData(char* data, qint64 maxLen)
             {
                 if (m_recordSilenceNbSamples <= 0)
                 {
-                    m_wavFileRecord->write(sl, sr);
+                    writeSampleToFile(sl, sr);
                     m_recordSilenceCount = 0;
                 }
                 else if (m_recordSilenceCount < m_recordSilenceNbSamples)
                 {
-                    m_wavFileRecord->write(sl, sr);
+                    writeSampleToFile(sl, sr);
                     m_recordSilenceCount++;
                 }
                 else
@@ -422,7 +431,7 @@ qint64 AudioOutputDevice::readData(char* data, qint64 maxLen)
                     m_wavFileRecord->startRecording();
                 }
 
-                m_wavFileRecord->write(sl, sr);
+                writeSampleToFile(sl, sr);
                 m_recordSilenceCount = 0;
             }
         }
@@ -431,6 +440,26 @@ qint64 AudioOutputDevice::readData(char* data, qint64 maxLen)
 	return samplesPerBuffer * 4;
 }
 
+void AudioOutputDevice::writeSampleToFile(qint16 lSample, qint16 rSample)
+{
+    switch (m_udpChannelMode)
+    {
+    case UDPChannelStereo:
+        m_wavFileRecord->write(lSample, rSample);
+        break;
+    case UDPChannelMixed:
+        m_wavFileRecord->writeMono((lSample+rSample)/2);
+        break;
+    case UDPChannelRight:
+        m_wavFileRecord->writeMono(rSample);
+        break;
+    case UDPChannelLeft:
+    default:
+        m_wavFileRecord->writeMono(lSample);
+        break;
+    }
+}
+
 qint64 AudioOutputDevice::writeData(const char* data, qint64 len)
 {
 	Q_UNUSED(data);

sdrbase/audio/audiooutputdevice.h

@@ -102,6 +102,7 @@ private:
 	//virtual bool open(OpenMode mode);
 	virtual qint64 readData(char* data, qint64 maxLen);
 	virtual qint64 writeData(const char* data, qint64 len);
+    void writeSampleToFile(qint16 lSample, qint16 rSample);
 
 	friend class AudioOutputPipe;
 };

sdrbase/dsp/wavfilerecord.cpp

@@ -37,7 +37,8 @@ WavFileRecord::WavFileRecord(quint32 sampleRate, quint64 centerFrequency) :
     m_recordOn(false),
     m_recordStart(false),
     m_byteCount(0),
-    m_msShift(0)
+    m_msShift(0),
+    m_nbChannels(2)
 {
     setObjectName("WavFileRecord");
 }
@@ -49,7 +50,8 @@ WavFileRecord::WavFileRecord(const QString& fileBase) :
     m_centerFrequency(0),
     m_recordOn(false),
     m_recordStart(false),
-    m_byteCount(0)
+    m_byteCount(0),
+    m_nbChannels(2)
 {
     setObjectName("WavFileRecord");
 }
@@ -124,6 +126,18 @@ void WavFileRecord::write(qint16 lSample, qint16 rSample)
     m_byteCount += 4;
 }
 
+void WavFileRecord::writeMono(qint16 sample)
+{
+    if (m_recordStart)
+    {
+        writeHeader();
+        m_recordStart = false;
+    }
+
+    m_sampleFile.write(reinterpret_cast<const char*>(&sample), 2);
+    m_byteCount += 2;
+}
+
 void WavFileRecord::start()
 {
 }
@@ -229,11 +243,11 @@ void WavFileRecord::writeHeader()
     header.m_fmtHeader.m_id[3] = ' ';
     header.m_fmtHeader.m_size = 16;
     header.m_audioFormat = 1; // Linear PCM
-    header.m_numChannels = 2; // I/Q
+    header.m_numChannels = m_nbChannels; // 2 for I/Q
     header.m_sampleRate = m_sampleRate;
     // We always use 16-bits regardless of SDR_RX_SAMP_SZ
-    header.m_byteRate = m_sampleRate * 2 * 16 / 8;
+    header.m_byteRate = m_sampleRate * m_nbChannels * 16 / 8;
-    header.m_blockAlign = 2 * 16 / 8;
+    header.m_blockAlign = m_nbChannels * 16 / 8;
     header.m_bitsPerSample = 16;
 
     header.m_auxiHeader.m_id[0] = 'a';

sdrbase/dsp/wavfilerecord.h

@@ -93,11 +93,13 @@ public:
     void setMsShift(qint64 shift) override { m_msShift = shift; }
     virtual int getBytesPerSample() override { return 4; };
     const QString& getCurrentFileName() override { return m_currentFileName; }
+    void setMono(bool mono) { m_nbChannels = mono ? 1 : 2; }
 
     void genUniqueFileName(uint deviceUID, int istream = -1);
 
     virtual void feed(const SampleVector::const_iterator& begin, const SampleVector::const_iterator& end, bool positiveOnly) override;
     void write(qint16 lSample, qint16 rSample); //!< write a single sample
+    void writeMono(qint16 sample); //!< write a single mono sample
     virtual void start() override;
     virtual void stop() override;
     virtual bool handleMessage(const Message& message) override;
@@ -124,6 +126,7 @@ private:
     QString m_currentFileName;
     quint64 m_byteCount;
     qint64 m_msShift;
+    int m_nbChannels;
 
     void writeHeader();
 };