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Switched to being explicitly careful about not wrapping around and stomping on data not yet output.

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This commit is contained in:
Thomas Harte 2016-01-18 13:56:20 -06:00
parent ddcc34740b
commit b70fdc2de8
1 changed files with 45 additions and 34 deletions
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29
OSBindings/Mac/Clock Signal/Wrappers/AudioQueue.m
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@ -13,12 +13,18 @@
#define AudioQueueStreamLength 2048
#define AudioQueueBufferLength 512
enum {
AudioQueueCanWrite,
AudioQueueWait
};
@implementation AudioQueue
{
AudioQueueRef _audioQueue;
AudioQueueBufferRef _audioBuffers[AudioQueueNumAudioBuffers];
unsigned int _audioStreamReadPosition, _audioStreamWritePosition;
int16_t _audioStream[AudioQueueStreamLength];
NSConditionLock *_writeLock;
}
@ -27,11 +33,11 @@
- (void)audioQueue:(AudioQueueRef)theAudioQueue didCallbackWithBuffer:(AudioQueueBufferRef)buffer
{
@synchronized(self)
{
[_writeLock lock];
const unsigned int writeLead = _audioStreamWritePosition - _audioStreamReadPosition;
const size_t audioDataSampleSize = buffer->mAudioDataByteSize / sizeof(int16_t);
if(writeLead >= audioDataSampleSize)
if(writeLead >= audioDataSampleSize*2)
{
size_t samplesBeforeOverflow = AudioQueueStreamLength - (_audioStreamReadPosition % AudioQueueStreamLength);
if(audioDataSampleSize <= samplesBeforeOverflow)
@ -51,7 +57,8 @@
memset(buffer->mAudioData, 0, buffer->mAudioDataByteSize);
}
AudioQueueEnqueueBuffer(theAudioQueue, buffer, 0, NULL);
}
[_writeLock unlockWithCondition:AudioQueueCanWrite];
}
static void audioOutputCallback(
@ -68,10 +75,10 @@ static void audioOutputCallback(
if(self)
{
_writeLock = [[NSConditionLock alloc] initWithCondition:AudioQueueCanWrite];
/*
Describe a mono, 16bit, 44.1Khz audio format
*/
AudioStreamBasicDescription outputDescription;
@ -123,8 +130,7 @@ static void audioOutputCallback(
- (void)enqueueAudioBuffer:(const int16_t *)buffer numberOfSamples:(size_t)lengthInSamples
{
@synchronized(self)
{
[_writeLock lockWhenCondition:AudioQueueCanWrite];
size_t samplesBeforeOverflow = AudioQueueStreamLength - (_audioStreamWritePosition % AudioQueueStreamLength);
if(samplesBeforeOverflow < lengthInSamples)
@ -138,7 +144,12 @@ static void audioOutputCallback(
}
_audioStreamWritePosition += lengthInSamples;
}
[_writeLock unlockWithCondition:[self writeLockCondition]];
}
- (NSInteger)writeLockCondition
{
return ((_audioStreamWritePosition - _audioStreamReadPosition) < AudioQueueStreamLength) ? AudioQueueCanWrite : AudioQueueWait;
}
@end