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Use a wait-free algorithm for audio queueing to minimize audio hiccups. This closes #8
This commit is contained in:
Cameron Gutman
parent
cf5b2ccbb4
commit
3ce2d68250
142
auddec.cpp
142
auddec.cpp
@ -1,138 +1,84 @@
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#include "moonlight.hpp"
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#define MAX_CHANNEL_COUNT 6
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#define MAX_CHANNEL_COUNT 2
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#define FRAME_SIZE 240
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typedef struct decoded_sample_entry {
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struct decoded_sample_entry *next;
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int sampleLength;
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short sampleBuffer[1];
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} decoded_sample_entry_t;
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#define CIRCULAR_BUFFER_SIZE 32
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#define MAX_QUEUE_LENGTH 14
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#define QUEUE_PRUNING_LENGTH 7
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// This code uses volatiles for synchronization between the producer and consumer side. This is
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// only safe because this code executes under very specific conditions, namely that the framework
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// ensures AudioPlayerSampleCallback and AudDecDecodeAndPlaySample are each only active on one thread
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// at a time.
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static int s_OpusChannelCount;
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static decoded_sample_entry_t* s_SampleQueueHead;
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static decoded_sample_entry_t* s_SampleQueueTail;
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static int s_SampleQueueLength;
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static pthread_mutex_t s_SampleQueueLock;
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static void ReapSampleQueue() {
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decoded_sample_entry_t *entry;
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while (s_SampleQueueHead) {
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entry = s_SampleQueueHead->next;
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free(s_SampleQueueHead);
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s_SampleQueueHead = entry;
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}
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s_SampleQueueTail = NULL;
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s_SampleQueueLength = 0;
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}
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static short s_CircularBuffer[CIRCULAR_BUFFER_SIZE][FRAME_SIZE * MAX_CHANNEL_COUNT];
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static int s_ReadIndex = 0;
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static int s_WriteIndex = 0;
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static void AudioPlayerSampleCallback(void* samples, uint32_t buffer_size, void* data) {
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unsigned char* buffer = (unsigned char *)samples;
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int offset = 0;
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pthread_mutex_lock(&s_SampleQueueLock);
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while (s_SampleQueueHead && s_SampleQueueHead->sampleLength <= buffer_size - offset) {
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decoded_sample_entry_t* lastEnt;
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// It should only ask us for complete buffers
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assert(buffer_size == FRAME_SIZE * MAX_CHANNEL_COUNT * sizeof(short));
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memcpy(&buffer[offset], s_SampleQueueHead->sampleBuffer, s_SampleQueueHead->sampleLength);
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offset += s_SampleQueueHead->sampleLength;
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// If the indexes aren't equal, we have a sample
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if (s_WriteIndex != s_ReadIndex) {
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memcpy(samples, s_CircularBuffer[s_ReadIndex], buffer_size);
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lastEnt = s_SampleQueueHead;
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s_SampleQueueHead = s_SampleQueueHead->next;
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free(lastEnt);
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s_SampleQueueLength--;
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// Use a full memory barrier to ensure the circular buffer is read before incrementing the index
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__sync_synchronize();
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// Remove another sample if we're in pruning mode
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if (s_SampleQueueLength > QUEUE_PRUNING_LENGTH) {
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lastEnt = s_SampleQueueHead;
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s_SampleQueueHead = s_SampleQueueHead->next;
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free(lastEnt);
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s_SampleQueueLength--;
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}
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// This can race with the reader in the AudDecDecodeAndPlaySample function. This is
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// not a problem because at worst, it just won't see that we've consumed this sample yet.
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s_ReadIndex = (s_ReadIndex + 1) % CIRCULAR_BUFFER_SIZE;
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}
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if (!s_SampleQueueHead) {
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s_SampleQueueTail = NULL;
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}
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pthread_mutex_unlock(&s_SampleQueueLock);
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// Zero the remaining portion of the sample buffer to reduce noise when underflowing
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if (buffer_size != offset) {
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memset(&buffer[offset], 0, buffer_size - offset);
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else {
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memset(samples, 0, buffer_size);
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}
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}
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void MoonlightInstance::AudDecInit(int audioConfiguration, POPUS_MULTISTREAM_CONFIGURATION opusConfig) {
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int rc;
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pthread_mutex_init(&s_SampleQueueLock, NULL);
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s_OpusChannelCount = opusConfig->channelCount;
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g_Instance->m_OpusDecoder = opus_multistream_decoder_create(opusConfig->sampleRate,
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opusConfig->channelCount,
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opusConfig->streams,
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opusConfig->coupledStreams,
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opusConfig->mapping,
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&rc);
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pp::AudioConfig audioConfig = pp::AudioConfig(g_Instance, PP_AUDIOSAMPLERATE_48000, FRAME_SIZE * 3);
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g_Instance->m_AudioPlayer = pp::Audio(g_Instance, audioConfig, AudioPlayerSampleCallback, NULL);
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g_Instance->m_AudioPlayer = pp::Audio(g_Instance, pp::AudioConfig(g_Instance, PP_AUDIOSAMPLERATE_48000, FRAME_SIZE),
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AudioPlayerSampleCallback, NULL);
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// Start playback now
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g_Instance->m_AudioPlayer.StartPlayback();
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}
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void MoonlightInstance::AudDecCleanup(void) {
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pthread_mutex_destroy(&s_SampleQueueLock);
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void MoonlightInstance::AudDecCleanup(void) {
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// Stop playback
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g_Instance->m_AudioPlayer.StopPlayback();
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if (g_Instance->m_OpusDecoder) {
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opus_multistream_decoder_destroy(g_Instance->m_OpusDecoder);
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}
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ReapSampleQueue();
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}
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void MoonlightInstance::AudDecDecodeAndPlaySample(char* sampleData, int sampleLength) {
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decoded_sample_entry_t* entry = (decoded_sample_entry_t*)malloc(sizeof(decoded_sample_entry_t) +
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(s_OpusChannelCount * FRAME_SIZE * sizeof(short)));
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if (entry) {
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int decodeLen = opus_multistream_decode(g_Instance->m_OpusDecoder, (unsigned char *)sampleData, sampleLength,
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entry->sampleBuffer, FRAME_SIZE, 0);
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if (decodeLen > 0) {
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entry->sampleLength = decodeLen * s_OpusChannelCount * sizeof(short);
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entry->next = NULL;
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pthread_mutex_lock(&s_SampleQueueLock);
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if (s_SampleQueueLength == MAX_QUEUE_LENGTH) {
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printf("Reaped sample queue\n");
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ReapSampleQueue();
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}
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if (!s_SampleQueueTail) {
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s_SampleQueueHead = s_SampleQueueTail = entry;
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}
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else {
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s_SampleQueueTail->next = entry;
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s_SampleQueueTail = entry;
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}
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s_SampleQueueLength++;
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pthread_mutex_unlock(&s_SampleQueueLock);
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}
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else {
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free(entry);
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}
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int decodeLen;
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// Check if there is space for this sample in the buffer. Again, this can race
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// but in the worst case, we'll not see the sample callback having consumed a sample.
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if (((s_WriteIndex + 1) % CIRCULAR_BUFFER_SIZE) == s_ReadIndex) {
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return;
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}
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decodeLen = opus_multistream_decode(g_Instance->m_OpusDecoder, (unsigned char *)sampleData, sampleLength,
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s_CircularBuffer[s_WriteIndex], FRAME_SIZE, 0);
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if (decodeLen > 0) {
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// Use a full memory barrier to ensure the circular buffer is written before incrementing the index
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__sync_synchronize();
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// This can race with the reader in the sample callback, however this is a benign
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// race since we'll either read the original value of s_WriteIndex (which is safe,
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// we just won't consider this sample) or the new value of s_WriteIndex
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s_WriteIndex = (s_WriteIndex + 1) % CIRCULAR_BUFFER_SIZE;
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}
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}
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