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Remove latency drop logic and replace by single frame writes

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This commit is contained in:
Cameron Gutman 2018-12-25 14:05:17 -08:00
parent cfabaf334e
commit 14cb2e1999
2 changed files with 12 additions and 28 deletions
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39
app/streaming/audio/renderers/soundioaudiorenderer.cpp
View file

@ -17,6 +17,7 @@ SoundIoAudioRenderer::SoundIoAudioRenderer()
m_Device(nullptr),
m_OutputStream(nullptr),
m_RingBuffer(nullptr),
m_Latency(0),
m_Errored(false)
{
@ -24,6 +25,10 @@ SoundIoAudioRenderer::SoundIoAudioRenderer()
SoundIoAudioRenderer::~SoundIoAudioRenderer()
{
SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
"Audio latency: %f",
m_Latency);
if (m_OutputStream != nullptr) {
soundio_outstream_destroy(m_OutputStream);
}
@ -330,41 +335,19 @@ void SoundIoAudioRenderer::sioWriteCallback(SoundIoOutStream* stream, int frameC
(me->m_OpusChannelCount * stream->bytes_per_sample);
int bytesRead = 0;
// Clamp framesLeft to frameCountMax
framesLeft = qMin(framesLeft, frameCountMax);
// Ensure we always write at least a buffer, even if it's silence, to avoid
// busy looping when no audio data is available while libsoundio tries to keep
// us from starving the output device.
frameCountMin = qMax(frameCountMin, (int)(stream->sample_rate * k_RawSampleLengthSec));
frameCountMin = qMin(frameCountMin, frameCountMax);
// Place an upper-bound on audio stream latency to
// avoid accumulating packets in queue-based backends
// like WASAPI, ALSA, and PulseAudio.
//
// This bound was set by testing on several Windows machines.
// The highest latency was found on a XPS 9343 running Windows 7
// in Steam Big Picture and the 5.1 audio test clip from Fraunhofer.
if (me->m_SoundIo->current_backend != SoundIoBackendCoreAudio && me->m_SoundIo->current_backend != SoundIoBackendJack) {
double latency;
if (soundio_outstream_get_latency(stream, &latency) == SoundIoErrorNone) {
if (latency > 0.050) {
// If our latency is higher than desired, drop these samples to gracefully lower
// the latency without glitching too much. Dropping the whole buffer causes
// a much more noticeable glitch. This approach also ensures that we don't
// accidentally underflow if the driver/kernel side is delayed and isn't
// consuming data fast enough. Dropping a frame at a time and re-evaluating
// each time ensures that we'll stop dropping if latency returns to normal.
readPtr += framesLeft * stream->bytes_per_sample * me->m_OpusChannelCount;
bytesRead += framesLeft * stream->bytes_per_sample * me->m_OpusChannelCount;
framesLeft = 0;
// Clamp framesLeft to frameCountMin to ensure that we never write more than one sample.
// This makes sure that we never increase our latency beyond what the sink is consuming.
framesLeft = qMin(framesLeft, frameCountMin);
SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
"Latency exceeded drop cap: %f",
latency);
}
}
// Track latency on queueing-based backends
if (me->m_SoundIo->current_backend != SoundIoBackendCoreAudio && me->m_SoundIo->current_backend != SoundIoBackendJack) {
soundio_outstream_get_latency(stream, &me->m_Latency);
}
for (;;) {

1
app/streaming/audio/renderers/soundioaudiorenderer.h
View file

@ -32,6 +32,7 @@ private:
struct SoundIoOutStream* m_OutputStream;
struct SoundIoRingBuffer* m_RingBuffer;
struct SoundIoChannelLayout m_EffectiveLayout;
double m_Latency;
bool m_Errored;
static const double k_RawSampleLengthSec;