iPhone playback AudioQueue stops/fails to continue after pausing at a breakpoint during debugging

For some reason, it seems that stopping at a breakpoint during debugging will kill my audio queue playback.

1. AudioQueue will be playing audio output.
2. Trigger a breakpoint to pause my iPhone app.
3. Subsequent resume, audio no longer gets played.
4. ( However, AudioQueue callback functions are still getting called.)
5. ( No AudioSession or AudioQueue errors are found.)

Since the debugger pauses the application (rather than an incoming phone call, for example开发者_如何学Python) , it's not a typical iPhone interruption, so AudioSession interruption callbacks do not get triggered like in this solution.

I am using three AudioQueue buffers at 4096 samples at 22kHz and filling them in a circular manner.

Problem occurs for both multi-threaded and single-threaded mode.

• Is there some known problem that you can't pause and resume AudioSessions or AudioQueues during a debugging session?
• Is it running out of "queued buffers" and it's destroying/killing the AudioQueue object (but then my AQ callback shouldn't trigger).

Anyone have insight into inner workings of iPhone AudioQueues?

After playing around with it for the last several days, before posting to StackOverflow, I figured out the answer just today. Go figure!

Just recreate the AudioQueue again by calling my "preparation functions"

SetupNewQueue(mDataFormat.mSampleRate, mDataFormat.mChannelsPerFrame);
StartQueue(true);

So detect when your AudioQueue may have "died". In my case, I would be writing data into an input buffer to be "pulled" by AudioQueue callback. If it doesn't occur in a certain time, or after X number of bytes of input buffer have been filled, I then recreate the AudioQueue.

This seems to solve the issue where "halts/fails" audio when you hit a debugging breakpoint.

The simplified versions of these functions are the following:

void AQPlayer::SetupNewQueue(double inSampleRate, UInt32 inChannelsPerFrame)
{
    //Prep AudioStreamBasicDescription
    mDataFormat.mSampleRate = inSampleRate;
    mDataFormat.SetCanonical(inChannelsPerFrame, YES);

    XThrowIfError(AudioQueueNewOutput(&mDataFormat, AQPlayer::AQBufferCallback, this, 
                                    NULL, kCFRunLoopCommonModes, 0, &mQueue), "AudioQueueNew failed");

    // adjust buffer size to represent about a half second of audio based on this format
    CalculateBytesForTime(mDataFormat, kBufferDurationSeconds, &mBufferByteSize, &mNumPacketsToRead);
    ctl->cmsg(CMSG_INFO, VERB_NOISY, "AQPlayer Buffer Byte Size: %d, Num Packets to Read: %d\n", (int)mBufferByteSize, (int)mNumPacketsToRead);

    mBufferWaitTime = mNumPacketsToRead / mDataFormat.mSampleRate * 0.9;

    XThrowIfError(AudioQueueAddPropertyListener(mQueue, kAudioQueueProperty_IsRunning, isRunningProc, this), "adding property listener");

    //Allocate AQ buffers (assume we are using CBR (constant bitrate)
    for (int i = 0; i < kNumberBuffers; ++i) {
        XThrowIfError(AudioQueueAllocateBuffer(mQueue, mBufferByteSize, &mBuffers[i]), "AudioQueueAllocateBuffer failed");
    }
...
}

OSStatus AQPlayer::StartQueue(BOOL inResume)
{   
// if we are not resuming, we also should restart the file read index
    if (!inResume)
        mCurrentPacket = 0; 

    // prime the queue with some data before starting
    for (int i = 0; i < kNumberBuffers; ++i) {
        mBuffers[i]->mAudioDataByteSize = mBuffers[i]->mAudioDataBytesCapacity;
        memset( mBuffers[i]->mAudioData, 0, mBuffers[i]->mAudioDataByteSize );

        XThrowIfError(AudioQueueEnqueueBuffer( mQueue,
                                mBuffers[i],
                                0,
                                NULL ),"AudioQueueEnqueueBuffer failed");
    }

    OSStatus status;
    status = AudioSessionSetActive( true );
    XThrowIfError(status, "\n\n*** AudioSession failed to become active *** \n\n");

    status = AudioQueueStart(mQueue, NULL);
    XThrowIfError(status, "\n\n*** AudioQueue failed to start *** \n\n");

    return status;
}