Indicate audio FIFO underflow/overflow. Don't zero pad audio output, if some audio is available.

plugins/channelrx/demodwfm/wfmdemod.h

@@ -95,6 +95,7 @@ public:
 	double getMagSq() const { return m_running ? m_basebandSink->getMagSq() : 0.0; }
     bool getSquelchOpen() const { return m_running && m_basebandSink->getSquelchOpen(); }
     int getAudioSampleRate() const { return m_running ? m_basebandSink->getAudioSampleRate() : 0; }
+    QDateTime getAudioFifoErrorDateTime() const { return m_running ? m_basebandSink->getAudioFifoErrorDateTime() : QDateTime(); }
 
     void getMagSqLevels(double& avg, double& peak, int& nbSamples)
     {

plugins/channelrx/demodwfm/wfmdemodbaseband.cpp

@@ -44,6 +44,8 @@ WFMDemodBaseband::WFMDemodBaseband()
     m_channelSampleRate = 0;
 
     connect(&m_inputMessageQueue, SIGNAL(messageEnqueued()), this, SLOT(handleInputMessages()));
+    connect(m_sink.getAudioFifo(), &AudioFifo::underflow, this, &WFMDemodBaseband::audioUnderflow);
+    connect(m_sink.getAudioFifo(), &AudioFifo::overflow, this, &WFMDemodBaseband::audioOverflow);
 }
 
 WFMDemodBaseband::~WFMDemodBaseband()
@@ -188,3 +190,13 @@ void WFMDemodBaseband::setBasebandSampleRate(int sampleRate)
     m_channelizer->setBasebandSampleRate(sampleRate);
     m_sink.applyChannelSettings(m_channelizer->getChannelSampleRate(), m_channelizer->getChannelFrequencyOffset());
 }
+
+void WFMDemodBaseband::audioUnderflow()
+{
+    m_audioFifoErrorDateTime = QDateTime::currentDateTime();
+}
+
+void WFMDemodBaseband::audioOverflow()
+{
+    m_audioFifoErrorDateTime = QDateTime::currentDateTime();
+}

plugins/channelrx/demodwfm/wfmdemodbaseband.h

@@ -20,6 +20,7 @@
 
 #include <QObject>
 #include <QRecursiveMutex>
+#include <QDateTime>
 
 #include "dsp/samplesinkfifo.h"
 #include "util/message.h"
@@ -73,6 +74,7 @@ public:
     void setChannel(ChannelAPI *channel);
     void setFifoLabel(const QString& label) { m_sampleFifo.setLabel(label); }
     void setAudioFifoLabel(const QString& label) { m_sink.setAudioFifoLabel(label); }
+    QDateTime getAudioFifoErrorDateTime() { return m_audioFifoErrorDateTime; }
 
 private:
     SampleSinkFifo m_sampleFifo;
@@ -82,6 +84,7 @@ private:
 	MessageQueue m_inputMessageQueue; //!< Queue for asynchronous inbound communication
     WFMDemodSettings m_settings;
     QRecursiveMutex m_mutex;
+    QDateTime m_audioFifoErrorDateTime;
 
     bool handleMessage(const Message& cmd);
     void applySettings(const WFMDemodSettings& settings, bool force = false);
@@ -89,6 +92,8 @@ private:
 private slots:
     void handleInputMessages();
     void handleData(); //!< Handle data when samples have to be processed
+    void audioUnderflow();
+    void audioOverflow();
 };
 
 #endif // INCLUDE_WFMDEMODBASEBAND_H

plugins/channelrx/demodwfm/wfmdemodgui.cpp

@@ -218,7 +218,8 @@ WFMDemodGUI::WFMDemodGUI(PluginAPI* pluginAPI, DeviceUISet *deviceUISet, Baseban
     m_basebandSampleRate(1),
 	m_basicSettingsShown(false),
     m_squelchOpen(false),
-    m_audioSampleRate(-1)
+    m_audioSampleRate(-1),
+    m_recentAudioFifoError(false)
 {
 	setAttribute(Qt::WA_DeleteOnClose, true);
     m_helpURL = "plugins/channelrx/demodwfm/readme.md";
@@ -361,11 +362,15 @@ void WFMDemodGUI::tick()
 
     int audioSampleRate = m_wfmDemod->getAudioSampleRate();
     bool squelchOpen = m_wfmDemod->getSquelchOpen();
+    int secsSinceAudioFifoError = m_wfmDemod->getAudioFifoErrorDateTime().secsTo(QDateTime::currentDateTime());
+    bool recentAudioFifoError = (secsSinceAudioFifoError < 1) && squelchOpen;
 
-    if ((audioSampleRate != m_audioSampleRate) || (squelchOpen != m_squelchOpen))
+    if ((audioSampleRate != m_audioSampleRate) || (squelchOpen != m_squelchOpen) || (recentAudioFifoError != m_recentAudioFifoError))
     {
         if (audioSampleRate < 0) {
             ui->audioMute->setStyleSheet("QToolButton { background-color : red; }");
+        } else if (recentAudioFifoError) {
+            ui->audioMute->setStyleSheet("QToolButton { background-color : rgb(120,120,0); }");
         } else if (squelchOpen) {
             ui->audioMute->setStyleSheet("QToolButton { background-color : green; }");
         } else {
@@ -374,6 +379,7 @@ void WFMDemodGUI::tick()
 
         m_audioSampleRate = audioSampleRate;
         m_squelchOpen = squelchOpen;
+        m_recentAudioFifoError = recentAudioFifoError;
     }
 }
 

plugins/channelrx/demodwfm/wfmdemodgui.h

@@ -58,6 +58,7 @@ private:
     bool m_audioMute;
     bool m_squelchOpen;
     int m_audioSampleRate;
+    bool m_recentAudioFifoError;
 
 	WFMDemod* m_wfmDemod;
 	MessageQueue m_inputMessageQueue;

sdrbase/audio/audiofifo.h

@@ -68,6 +68,7 @@ private:
 signals:
 	void dataReady();
 	void overflow(int nsamples);
+    void underflow();
 };
 
 #endif // INCLUDE_AUDIOFIFO_H

sdrbase/audio/audiooutputdevice.cpp

@@ -369,6 +369,13 @@ qint64 AudioOutputDevice::readData(char* data, qint64 maxLen)
 		}
 	}
 
+    // See how much data we have available
+    // If we have less than the requested amount, we only output what we have
+    // If we have no data, then we output some zeros to avoid underflow
+    // (bytesAvailable() returns this amount when none available)
+    unsigned int samplesAvailable = bytesAvailable() / 4;
+    samplesPerBuffer = std::min(samplesAvailable, samplesPerBuffer);
+
 	memset(&m_mixBuffer[0], 0x00, 2 * samplesPerBuffer * sizeof(m_mixBuffer[0])); // start with silence
 
 	// sum up a block from all fifos
@@ -380,10 +387,11 @@ qint64 AudioOutputDevice::readData(char* data, qint64 maxLen)
 		const qint16* src = (const qint16*) data;
 		std::vector<qint32>::iterator dst = m_mixBuffer.begin();
 
-//		if (samples != framesPerBuffer)
-//		{
-//            qDebug("AudioOutputDevice::readData: read %d samples vs %d requested", samples, framesPerBuffer);
-//		}
+        if (samples != samplesPerBuffer)
+        {
+            //qDebug("AudioOutputDevice::readData: read %d samples vs %d requested", samples, samplesPerBuffer);
+            emit (*it)->underflow();
+        }
 
 		for (unsigned int i = 0; i < samples; i++)
 		{
@@ -541,8 +549,11 @@ qint64 AudioOutputDevice::bytesAvailable() const
     // If we return 0 from this twice in a row, audio will stop.
     // So we always return a value, and if we don't have enough data in the FIFOs
     // when readData is called, that will output silence
-    if (available == 0) {
-        available = 2048; // Is there a better value to use?
+    if (available == 0)
+    {
+        // Use a small value, so padding is minimized, but not too small, we get underflow again straightaway
+        // Could make this a function of sample rate
+        available = 512;
     }
     return available * 2 * 2; // 2 Channels of 16-bit data
 }