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Use a semaphore to prevent us from having to busy wait on the audio buffer queue

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This commit is contained in:
Cameron Gutman 2014-10-20 04:38:36 -04:00
parent e56923a71d
commit f3b3d2bd08
1 changed files with 21 additions and 2 deletions
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23
Limelight/Connection.m
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@ -11,6 +11,8 @@
#import <AudioUnit/AudioUnit.h> #import <AudioUnit/AudioUnit.h>
#import <AVFoundation/AVFoundation.h> #import <AVFoundation/AVFoundation.h>
#include <dispatch/dispatch.h>
#include "Limelight.h" #include "Limelight.h"
#include "opus.h" #include "opus.h"
@ -40,6 +42,7 @@ struct AUDIO_BUFFER_QUEUE_ENTRY {
static short decodedPcmBuffer[512]; static short decodedPcmBuffer[512];
static NSLock *audioLock; static NSLock *audioLock;
static struct AUDIO_BUFFER_QUEUE_ENTRY *audioBufferQueue; static struct AUDIO_BUFFER_QUEUE_ENTRY *audioBufferQueue;
static dispatch_semaphore_t audioQueueSemaphore;
static int audioBufferQueueLength; static int audioBufferQueueLength;
static AudioComponentInstance audioUnit; static AudioComponentInstance audioUnit;
static VideoDecoderRenderer* renderer; static VideoDecoderRenderer* renderer;
@ -92,6 +95,8 @@ void ArInit(void)
opusDecoder = opus_decoder_create(48000, 2, &err); opusDecoder = opus_decoder_create(48000, 2, &err);
audioLock = [[NSLock alloc] init]; audioLock = [[NSLock alloc] init];
audioQueueSemaphore = dispatch_semaphore_create(0);
} }
void ArRelease(void) void ArRelease(void)
@ -136,9 +141,15 @@ void ArDecodeAndPlaySample(char* sampleData, int sampleLength)
// Clear all values from the buffer queue // Clear all values from the buffer queue
struct AUDIO_BUFFER_QUEUE_ENTRY *entry; struct AUDIO_BUFFER_QUEUE_ENTRY *entry;
while (audioBufferQueue != NULL) { while (audioBufferQueue != NULL) {
// Unlink the current entry
entry = audioBufferQueue; entry = audioBufferQueue;
audioBufferQueue = entry->next; audioBufferQueue = entry->next;
// Decrease the semaphore count and queue length
audioBufferQueueLength--; audioBufferQueueLength--;
dispatch_semaphore_wait(audioQueueSemaphore, DISPATCH_TIME_NOW);
// Free the entry
free(entry); free(entry);
} }
} }
@ -153,9 +164,13 @@ void ArDecodeAndPlaySample(char* sampleData, int sampleLength)
} }
lastEntry->next = newEntry; lastEntry->next = newEntry;
} }
audioBufferQueueLength++;
// Increment the queue size and unlock
audioBufferQueueLength++;
[audioLock unlock]; [audioLock unlock];
// Signal the other thread
dispatch_semaphore_signal(audioQueueSemaphore);
} }
} }
} }
@ -319,10 +334,13 @@ static OSStatus playbackCallback(void *inRefCon,
} }
// Wait for a buffer to be available // Wait for a buffer to be available
// FIXME: This needs optimization to avoid busy waiting for buffers
struct AUDIO_BUFFER_QUEUE_ENTRY *audioEntry = NULL; struct AUDIO_BUFFER_QUEUE_ENTRY *audioEntry = NULL;
while (audioEntry == NULL) while (audioEntry == NULL)
{ {
// Wait for an entry to be present in the queue
dispatch_semaphore_wait(audioQueueSemaphore, DISPATCH_TIME_FOREVER);
// If there's an entry there, dequeue it
[audioLock lock]; [audioLock lock];
if (audioBufferQueue != NULL) { if (audioBufferQueue != NULL) {
// Dequeue this entry temporarily // Dequeue this entry temporarily
@ -351,6 +369,7 @@ static OSStatus playbackCallback(void *inRefCon,
audioBufferQueue = audioEntry; audioBufferQueue = audioEntry;
audioBufferQueueLength++; audioBufferQueueLength++;
[audioLock unlock]; [audioLock unlock];
dispatch_semaphore_signal(audioQueueSemaphore);
} }
else { else {
// This entry is fully depleted so free it // This entry is fully depleted so free it