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Batch audio frames on Steam Link to save CPU cycles

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This commit is contained in:
Cameron Gutman 2019-04-28 12:55:04 -07:00
parent 477fa8fedf
commit 2bf552f801
2 changed files with 37 additions and 5 deletions
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39
app/streaming/audio/renderers/slaud.cpp
View file

@ -2,9 +2,16 @@
#include <SDL.h>
// To reduce CPU load on the Steam Link, we need to accumulate several frames
// before submitting for playback. Higher frames per submission saves more CPU
// but increases audio latency.
#define FRAMES_PER_SUBMISSION 4
SLAudioRenderer::SLAudioRenderer()
: m_AudioContext(nullptr),
m_AudioStream(nullptr)
m_AudioStream(nullptr),
m_AudioBuffer(nullptr),
m_AudioBufferBytesFilled(0)
{
SLAudio_SetLogFunction(SLAudioRenderer::slLogCallback, nullptr);
}
@ -18,10 +25,11 @@ bool SLAudioRenderer::prepareForPlayback(const OPUS_MULTISTREAM_CONFIGURATION* o
return false;
}
m_AudioBufferSize = SAMPLES_PER_FRAME * sizeof(short) * opusConfig->channelCount * FRAMES_PER_SUBMISSION;
m_AudioStream = SLAudio_CreateStream(m_AudioContext,
opusConfig->sampleRate,
opusConfig->channelCount,
SAMPLES_PER_FRAME * sizeof(short) * opusConfig->channelCount,
m_AudioBufferSize,
1);
if (m_AudioStream == nullptr) {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
@ -37,6 +45,14 @@ bool SLAudioRenderer::prepareForPlayback(const OPUS_MULTISTREAM_CONFIGURATION* o
SLAudioRenderer::~SLAudioRenderer()
{
if (m_AudioBufferBytesFilled != 0) {
// We had a buffer in flight when we quit. Just in case
// SLAudio doesn't handle this properly, we'll zero and submit
// it just to be safe.
memset(m_AudioBuffer, 0, m_AudioBufferSize);
SLAudio_SubmitFrame(m_AudioStream);
}
if (m_AudioStream != nullptr) {
SLAudio_FreeStream(m_AudioStream);
}
@ -48,11 +64,24 @@ SLAudioRenderer::~SLAudioRenderer()
bool SLAudioRenderer::submitAudio(short* audioBuffer, int audioSize)
{
void* outputBuffer = SLAudio_BeginFrame(m_AudioStream);
if (m_AudioBufferBytesFilled == 0) {
// Get a new audio buffer from SLAudio
m_AudioBuffer = (char*)SLAudio_BeginFrame(m_AudioStream);
if (m_AudioBuffer == nullptr) {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "SLAudio_BeginFrame() failed");
return true;
}
}
if (outputBuffer != nullptr) {
memcpy(outputBuffer, audioBuffer, audioSize);
// Accumulate several frames of audio before submitting to reduce CPU load
SDL_assert(audioSize <= m_AudioBufferSize - m_AudioBufferBytesFilled);
memcpy(&m_AudioBuffer[m_AudioBufferBytesFilled], audioBuffer, audioSize);
m_AudioBufferBytesFilled += audioSize;
// Submit the buffer when it's full
if (m_AudioBufferBytesFilled == m_AudioBufferSize) {
SLAudio_SubmitFrame(m_AudioStream);
m_AudioBufferBytesFilled = 0;
}
return true;

3
app/streaming/audio/renderers/slaud.h
View file

@ -19,4 +19,7 @@ private:
CSLAudioContext* m_AudioContext;
CSLAudioStream* m_AudioStream;
char* m_AudioBuffer;
int m_AudioBufferSize;
int m_AudioBufferBytesFilled;
};