CODEWITHSUNDEEP
c++objective-ccopenal
Rad'Val
Rad'Val

Reputation: 9241

Silence between played buffers in OpenAL?

I use alSourceQueueBuffers to stream buffers into a AL sound source. I have buffers of different size that need to be played one after another. So far so good, however, between some buffer I need a variable amount of silence, how can I add it programmatic?

Upvotes: 0

Views: 847

Answers (1)

JCooper
JCooper

Reputation: 6525

Perhaps the easiest way would be to generate buffers that hold silence of the length needed and queue them appropriately. You just need to make an array full of zeros based on the sample rate and the desired length of silence and pass it into the buffer.

If you want things to be more complicated, then you can't queue all of the buffers. You queue the one that needs to play right now and set a timer for when it will be done (and the amount of silent time has also passed). Then you can queue the next buffer. Or you can poll the source to see if it has stopped and when it does, start counting down the silent time. You could also use the streaming functionality...

Edit: This worked for me. Sample rate needs to be the same as other buffers queued on your source. You could also have a 'greatest common denominator' length buffer and just queue it up multiple times.

int sampleRate=22050;
double sTime=2.5;     // How long to maintain silence.
int sampleCount= int(sTime*sampleRate);
int byteCount  = sampleCount*sizeof(short);
short* silence = (short*)malloc(byteCount);
memset(silence,0,byteCount);

alBufferData(silenceBuffer,AL_FORMAT_MONO16,silence,byteCount,sampleRate);
alSourceQueueBuffers(mySource,1,&silenceBuffer);

free(silence);

Upvotes: 2

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