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QAudioOutput: low-latency related changes.

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- Decrease timer period to 10ms;
- Set PulseAudio buffer size if specified by the user;
- Set PulseAudio buffer size to 40ms if not specified;
- Always request 1 chunk of data at a time in pull mode;

Change-Id: If95c097c67c3342f733bde9e699518741d7ef991
Reviewed-by: Dmytro Poplavskiy <dmytro.poplavskiy@nokia.com>
This commit is contained in:
Lev Zelenskiy
2012-05-08 14:06:30 +10:00
committed by Qt by Nokia
parent 68680fc661
commit db9a6de400
2 changed files with 40 additions and 15 deletions
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53
src/plugins/pulseaudio/qaudiooutput_pulse.cpp
View File

@@ -53,8 +53,11 @@
QT_BEGIN_NAMESPACE QT_BEGIN_NAMESPACE
const int PeriodTimeMs = 20; const int PeriodTimeMs = 20;
const int LowLatencyPeriodTimeMs = 10;
const int LowLatencyBufferSizeMs = 40; const int LowLatencyBufferSizeMs = 40;
#define LOW_LATENCY_CATEGORY_NAME "game"
static void outputStreamWriteCallback(pa_stream *stream, size_t length, void *userdata) static void outputStreamWriteCallback(pa_stream *stream, size_t length, void *userdata)
{ {
Q_UNUSED(stream); Q_UNUSED(stream);
@@ -145,10 +148,12 @@ QPulseAudioOutput::QPulseAudioOutput(const QByteArray &device)
, m_pullMode(true) , m_pullMode(true)
, m_opened(false) , m_opened(false)
, m_audioSource(0) , m_audioSource(0)
, m_periodTime(0)
, m_stream(0) , m_stream(0)
, m_notifyInterval(1000) , m_notifyInterval(1000)
, m_periodSize(0) , m_periodSize(0)
, m_bufferSize(0) , m_bufferSize(0)
, m_maxBufferSize(0)
, m_totalTimeValue(0) , m_totalTimeValue(0)
, m_tickTimer(new QTimer(this)) , m_tickTimer(new QTimer(this))
, m_audioBuffer(0) , m_audioBuffer(0)
@@ -269,19 +274,19 @@ bool QPulseAudioOutput::open()
QPulseAudioEngine *pulseEngine = QPulseAudioEngine::instance(); QPulseAudioEngine *pulseEngine = QPulseAudioEngine::instance();
pa_threaded_mainloop_lock(pulseEngine->mainloop()); pa_threaded_mainloop_lock(pulseEngine->mainloop());
qint64 bytesPerSecond = m_format.sampleRate() * m_format.channels() * m_format.sampleSize() / 8;
pa_proplist *propList = pa_proplist_new(); pa_proplist *propList = pa_proplist_new();
if (m_category.isNull()) { if (m_category.isNull()) {
// Meant to be one of the strings "video", "music", "game", "event", "phone", "animation", "production", "a11y", "test" // Meant to be one of the strings "video", "music", "game", "event", "phone", "animation", "production", "a11y", "test"
// We choose music unless the buffer size is small, where we choose game.. // We choose music unless the buffer size is small, where we choose game..
qint64 bytesPerSecond = m_format.sampleRate() * m_format.channels() * m_format.sampleSize() / 8; if (m_bufferSize > 0 && bytesPerSecond > 0 && (m_bufferSize * 1000LL / bytesPerSecond <= LowLatencyBufferSizeMs)) {
if (m_bufferSize > 0 && bytesPerSecond > 0 && (m_bufferSize * 1000LL / bytesPerSecond < LowLatencyBufferSizeMs)) { m_category = LOW_LATENCY_CATEGORY_NAME;
pa_proplist_sets(propList, PA_PROP_MEDIA_ROLE, "game");
} else { } else {
pa_proplist_sets(propList, PA_PROP_MEDIA_ROLE, "music"); m_category = "music";
}
} }
} else {
pa_proplist_sets(propList, PA_PROP_MEDIA_ROLE, m_category.toLatin1().constData()); pa_proplist_sets(propList, PA_PROP_MEDIA_ROLE, m_category.toLatin1().constData());
}
m_stream = pa_stream_new_with_proplist(pulseEngine->context(), m_streamName.constData(), &spec, 0, propList); m_stream = pa_stream_new_with_proplist(pulseEngine->context(), m_streamName.constData(), &spec, 0, propList);
pa_proplist_free(propList); pa_proplist_free(propList);
@@ -302,7 +307,18 @@ bool QPulseAudioOutput::open()
} }
pa_cvolume_set(&m_chVolume, m_spec.channels, paVolume); pa_cvolume_set(&m_chVolume, m_spec.channels, paVolume);
if (pa_stream_connect_playback(m_stream, m_device.data(), NULL, (pa_stream_flags_t)0, &m_chVolume, NULL) < 0) { if (m_bufferSize <= 0 && m_category == LOW_LATENCY_CATEGORY_NAME) {
m_bufferSize = bytesPerSecond * LowLatencyBufferSizeMs / qint64(1000);
}
pa_buffer_attr requestedBuffer;
requestedBuffer.fragsize = (uint32_t)-1;
requestedBuffer.maxlength = (uint32_t)-1;
requestedBuffer.minreq = (uint32_t)-1;
requestedBuffer.prebuf = (uint32_t)-1;
requestedBuffer.tlength = m_bufferSize;
if (pa_stream_connect_playback(m_stream, m_device.data(), (m_bufferSize > 0) ? &requestedBuffer : NULL, (pa_stream_flags_t)0, &m_chVolume, NULL) < 0) {
qWarning() << "pa_stream_connect_playback() failed!"; qWarning() << "pa_stream_connect_playback() failed!";
return false; return false;
} }
@@ -311,9 +327,11 @@ bool QPulseAudioOutput::open()
pa_threaded_mainloop_wait(pulseEngine->mainloop()); pa_threaded_mainloop_wait(pulseEngine->mainloop());
} }
const pa_buffer_attr *buffer = pa_stream_get_buffer_attr(m_stream); const pa_buffer_attr *buffer = pa_stream_get_buffer_attr(m_stream);
m_periodSize = pa_usec_to_bytes(PeriodTimeMs*1000, &spec); m_periodTime = (m_category == LOW_LATENCY_CATEGORY_NAME) ? LowLatencyPeriodTimeMs : PeriodTimeMs;
m_bufferSize = qMin(m_periodSize * 5, int(buffer->maxlength)); m_periodSize = pa_usec_to_bytes(m_periodTime*1000, &spec);
m_audioBuffer = new char[buffer->maxlength]; m_bufferSize = buffer->tlength;
m_maxBufferSize = buffer->maxlength;
m_audioBuffer = new char[m_maxBufferSize];
#ifdef DEBUG_PULSE #ifdef DEBUG_PULSE
qDebug() << "Buffering info:"; qDebug() << "Buffering info:";
qDebug() << "\tMax length: " << buffer->maxlength; qDebug() << "\tMax length: " << buffer->maxlength;
@@ -326,7 +344,7 @@ bool QPulseAudioOutput::open()
pa_threaded_mainloop_unlock(pulseEngine->mainloop()); pa_threaded_mainloop_unlock(pulseEngine->mainloop());
m_opened = true; m_opened = true;
m_tickTimer->start(PeriodTimeMs); m_tickTimer->start(m_periodTime);
m_elapsedTimeOffset = 0; m_elapsedTimeOffset = 0;
m_timeStamp.restart(); m_timeStamp.restart();
@@ -383,9 +401,9 @@ void QPulseAudioOutput::userFeed()
if (chunks == 0) if (chunks == 0)
return; return;
int input = m_periodSize * chunks; int input = m_periodSize; // always request 1 chunk of data from user
if (input > m_bufferSize) if (input > m_maxBufferSize)
input = m_bufferSize; input = m_maxBufferSize;
int audioBytesPulled = m_audioSource->read(m_audioBuffer, input); int audioBytesPulled = m_audioSource->read(m_audioBuffer, input);
Q_ASSERT(audioBytesPulled <= input); Q_ASSERT(audioBytesPulled <= input);
@@ -397,6 +415,11 @@ void QPulseAudioOutput::userFeed()
} }
qint64 bytesWritten = write(m_audioBuffer, audioBytesPulled); qint64 bytesWritten = write(m_audioBuffer, audioBytesPulled);
Q_ASSERT(bytesWritten == audioBytesPulled); //unfinished write should not happen since the data provided is less than writableSize Q_ASSERT(bytesWritten == audioBytesPulled); //unfinished write should not happen since the data provided is less than writableSize
if (chunks > 1) {
// PulseAudio needs more data. Ask for it immediately.
QMetaObject::invokeMethod(this, "userFeed", Qt::QueuedConnection);
}
} }
} }
@@ -514,7 +537,7 @@ void QPulseAudioOutput::resume()
m_deviceState = QAudio::ActiveState; m_deviceState = QAudio::ActiveState;
m_errorState = QAudio::NoError; m_errorState = QAudio::NoError;
m_tickTimer->start(PeriodTimeMs); m_tickTimer->start(m_periodTime);
emit stateChanged(m_deviceState); emit stateChanged(m_deviceState);
} }

2
src/plugins/pulseaudio/qaudiooutput_pulse.h
View File

@@ -122,10 +122,12 @@ private:
bool m_opened; bool m_opened;
QIODevice *m_audioSource; QIODevice *m_audioSource;
QTimer m_periodTimer; QTimer m_periodTimer;
int m_periodTime;
pa_stream *m_stream; pa_stream *m_stream;
int m_notifyInterval; int m_notifyInterval;
int m_periodSize; int m_periodSize;
int m_bufferSize; int m_bufferSize;
int m_maxBufferSize;
QTime m_clockStamp; QTime m_clockStamp;
qint64 m_totalTimeValue; qint64 m_totalTimeValue;
QTimer *m_tickTimer; QTimer *m_tickTimer;