Audio Toolbox playing an mp3 file (iOS)

Question

Hello,

I've tried to get an mp3 file played with Audio Toolbox and Audio Queues, but whatever I try, I don't get anything played (neither in the simulator nor on the device). When I run it in the simulator it tells me:

"Prime failed (-66674); will stop (0/0 frames)",

so I think there is a basic mistake somewhere, maybe in the AudioEnqueueBuffer function, because there seems to be nothing in the queue afterwards. When I ask for the status, I always get 0 back.

I'm sorry that I have posted so much code, but I'm just not sure where the mistake is.

Please help me.

- (void)startPlayback{

 NSString *fileString = [[NSBundle mainBundle] pathForResource:@"musik" ofType:@"mp3"];

 const char *filePathAsCString = [fileString UTF8String];

 CFURLRef fileURL = CFURLCreateFromFileSystemRepresentation(NULL, (UInt8*)filePathAsCString, strlen(filePathAsCString), false);

    playState.currentPacket = 0;

    playState.dataFormat->mSampleRate = kAudioStreamAnyRate;
    playState.dataFormat->mFormatID = kAudioFormatMPEGLayer3;
    playState.dataFormat->mFramesPerPacket = 0;
    playState.dataFormat->mChannelsPerFrame = 2;
    playState.dataFormat->mBytesPerFrame = 0;
    playState.dataFormat->mBytesPerPacket = 0;
    playState.dataFormat->mBitsPerChannel = 0;
    playState.dataFormat->mReserved = 0;
    playState.dataFormat->mFormatFlags = 0;;

    OSStatus status;

    status = AudioFileOpenURL(fileURL, kAudioFileReadPermission, kAudioFileMP3Type, &playState.audioFile);

    if(status == 0)
    {
        status = AudioQueueNewOutput(
          &playState.dataFormat,
          MyAudioOutputCallback,
          &playState,
          CFRunLoopGetCurrent(),
          0,
          0,
          &playState.queue);

        if(status == 0)
        {
            playState.playing = true;
            for(int i = 0; i < 3 && playState.playing; i++)
            {
                if(playState.playing)
                {
                    AudioQueueAllocateBufferWithPacketDescriptions(playState.queue, 64000, sizeof(AudioStreamPacketDescription)*75, &playState.buffers[i]);
                    MyAudioOutputCallback(&playState, playState.queue, playState.buffers[i]);
                }
            }

            if(playState.playing)
            {
                status = AudioQueueStart(playState.queue, NULL);
                if(status == 0)
                {
                    NSLog(@"Playing");
                }
            }
        }        
    }

    if(status != 0)
    {
        NSLog(@"Play failed");
    }
}

And here the Callback function:

void MyAudioOutputCallback( void *inUserData,
       AudioQueueRef outAQ,
       AudioQueueBufferRef outBuffer)
{
    PlayState *playState= (PlayState *)inUserData;

    UInt32 bytesRead;
    UInt32 numPackets = 75;

    OSStatus status;
    status = AudioFileReadPackets(playState->audioFile, false, &bytesRead, outBuffer->mPacketDescriptions, playState->currentPacket, &numPackets, outBuffer->mAudioData);

    if(numPackets)
    {
        outBuffer->mAudioDataByteSize = bytesRead;
  outBuffer->mPacketDescriptionCount = numPackets;
        status = AudioQueueEnqueueBuffer(
           playState->queue,
           outBuffer,
           0,
           0);

  NSLog(@"EnqueueStatus: %d", status);
        playState->currentPacket += numPackets;

    }

}