Question

I am working with core audio using an AUFilePlayer to load a few mp3s into a mixer unit, everything plays great however I am unable to pause the music or rewind the music back to the start. I tried Starting and stopping the AudioGraph, but once the playback is stopped, I can’t get it to restart. I also tried using AudioUnitSetProperty to set the file playback to 0

i.e something along these lines:

        ScheduledAudioFileRegion rgn;
        memset (&rgn.mTimeStamp, 0, sizeof(rgn.mTimeStamp));
        rgn.mTimeStamp.mFlags = kAudioTimeStampSampleTimeValid;
        rgn.mTimeStamp.mSampleTime = 0;
        rgn.mCompletionProc = NULL;
        rgn.mCompletionProcUserData = NULL;
        rgn.mAudioFile = inputFile;
        rgn.mLoopCount = 1;
        rgn.mStartFrame = 0;

        rgn.mFramesToPlay = nPackets * inputFormat.mFramesPerPacket;

        AudioUnitSetProperty(fileUnit, kAudioUnitProperty_ScheduledFileRegion, 
                             kAudioUnitScope_Global, 0,&rgn, sizeof(rgn));

Any suggestions?

Answer 1

I figured it out. In case any of you ever run into the same problem, here was my solution:

1. On startup, I initialize the AUGraph with an array of file player audio units. I set the play head of each track in the file player audio unit array to zero.

2. On “pause” , first I stop the AuGraph. Then I loop through the array of file player audio units and capture the current playhead position. Each time the pause button is pressed, I make sure I add the new current playhead position to the old playhead position to get its true position.

3. When the user hits play, I re initialize the AuGraph just as if I was starting the app for the very first time, only I set the playhead to the number I stored when the user hit “pause” instead of telling it to play at the start of the file.

4. If the user clicks stop, I set the stored playhead position to zero and then stop the AuGraph.