How to implement pause function for Audio Units

Question

My code is based on this example and a stop function is already implemented, there are functions to uninitialize and stop the audio unit:

    AudioOutputUnitStop(toneUnit);
    AudioUnitUninitialize(toneUnit);
    AudioComponentInstanceDispose(toneUnit);
    toneUnit = nil;

In the example I linked to a pause function is not necessary since there's only one frequency being played so there's no difference between pause and stop. In my implementation however, I'm playing a range of different frequencies and I want to be able to pause playback.

Any ideas how this is done?

score 2 · Accepted Answer · answered Aug 21 '12 at 12:53

fade out (~10ms) the AUs' output, feed the output silence after the fade
remember the position you stopped reading your input signal
reset the AUs before you resume
resume from the position you recorded above (here, a fade in of the input signal to the AUs would be also be good)

score 0 · Answer 2 · answered Oct 31 '12 at 08:01

You can try writing 0 to the buffer when you playback. It is effectively a pause. Here's some code that you can use within the playback callback.

   NSLog(@"Playing silence!");

   for (int i = 0 ; i < ioData->mNumberBuffers; i++){
    //get the buffer to be filled
    AudioBuffer buffer = ioData->mBuffers[i];
    UInt32 *frameBuffer = buffer.mData;

    //loop through the buffer and fill the frames
       for (int j = 0; j < inNumberFrames; j++){
           frameBuffer[j] = 0;
       }
   }

How to implement pause function for Audio Units

2 Answers2