PulseAudio: fix playback for short streams in pull mode

If the provided stream's length is shorter than the stream prebuf
attribute, the stream will never play. We adjust the prebuf attribute
in this case.

Change-Id: Ia397ac967ad2fa357a7aba137fbb78de272440ed
Reviewed-by: Yoann Lopes <yoann.lopes@theqtcompany.com>

1 files changed, 32 insertions, 6 deletions

diff --git a/src/plugins/pulseaudio/qaudiooutput_pulse.cpp b/src/plugins/pulseaudio/qaudiooutput_pulse.cpp
index a654af86c..5d2ba8653 100644
--- a/src/plugins/pulseaudio/qaudiooutput_pulse.cpp
+++ b/src/plugins/pulseaudio/qaudiooutput_pulse.cpp
@@ -133,6 +133,18 @@ static void outputStreamDrainComplete(pa_stream *stream, int success, void *user
 #endif
 }
 
+static void streamAdjustPrebufferCallback(pa_stream *stream, int success, void *userdata)
+{
+    Q_UNUSED(stream);
+    Q_UNUSED(success);
+    Q_UNUSED(userdata);
+
+#ifdef DEBUG_PULSE
+    qDebug() << "Adjust prebuffer completed successfully: " << (bool)success;
+#endif
+}
+
+
 QPulseAudioOutput::QPulseAudioOutput(const QByteArray &device)
     : m_device(device)
     , m_errorState(QAudio::NoError)
@@ -207,17 +219,19 @@ void QPulseAudioOutput::start(QIODevice *device)
     // Handle change of mode
     if (m_audioSource && !m_pullMode) {
         delete m_audioSource;
-        m_audioSource = 0;
     }
+    m_audioSource = 0;
 
     close();
 
-    if (!open())
-        return;
-
     m_pullMode = true;
     m_audioSource = device;
 
+    if (!open()) {
+        m_audioSource = 0;
+        return;
+    }
+
     setState(QAudio::ActiveState);
 }
 
@@ -229,17 +243,18 @@ QIODevice *QPulseAudioOutput::start()
     // Handle change of mode
     if (m_audioSource && !m_pullMode) {
         delete m_audioSource;
-        m_audioSource = 0;
     }
+    m_audioSource = 0;
 
     close();
 
+    m_pullMode = false;
+
     if (!open())
         return Q_NULLPTR;
 
     m_audioSource = new PulseOutputPrivate(this);
     m_audioSource->open(QIODevice::WriteOnly|QIODevice::Unbuffered);
-    m_pullMode = false;
 
     setState(QAudio::IdleState);
 
@@ -349,6 +364,17 @@ bool QPulseAudioOutput::open()
     m_bufferSize = buffer->tlength;
     m_maxBufferSize = buffer->maxlength;
     m_audioBuffer = new char[m_maxBufferSize];
+
+    const qint64 streamSize = m_audioSource ? m_audioSource->size() : 0;
+    if (m_pullMode && streamSize > 0 && static_cast<qint64>(buffer->prebuf) > streamSize) {
+        pa_buffer_attr newBufferAttr;
+        newBufferAttr = *buffer;
+        newBufferAttr.prebuf = streamSize;
+        pa_operation *o = pa_stream_set_buffer_attr(m_stream, &newBufferAttr, streamAdjustPrebufferCallback, NULL);
+        if (o)
+            pa_operation_unref(o);
+    }
+
 #ifdef DEBUG_PULSE
     qDebug() << "Buffering info:";
     qDebug() << "\tMax length: " << buffer->maxlength;