Problem with waveOutWrite and waveOutGetPosition deadlock

Question

I\'m working on an app that plays audio continuously using the waveOut... API from winmm.dll. The app uses \"leapfrog\" buffers, which are basically a

Answer 1

It deadlocks inside the mmsys API code. Calling waveOutGetPosition() inside the callback deadlocks when the main thread is busy executing waveOutWrite(). It is fixable, you'll need a lock so these two functions cannot execute at the same time. Add this field to LeapFrogPlayer:

    private object mLocker = new object();

And use it in GetElapsedMilliseconds():

        if (!noAPIcall)
        {
          lock (mLocker) {
            ret = WaveOutX.waveOutGetPosition(_hWaveOut, ref _timestruct,
                _timestructsize);
          }
        }

and HandleWaveCallback():

        // play the next buffer
        lock (mLocker) {
          int ret = WaveOutX.waveOutWrite(_hWaveOut, ref _header[_currentBuffer],
              Marshal.SizeOf(_header[_currentBuffer]));
          if (ret != WaveOutX.MMSYSERR_NOERROR) {
            throw new Exception("error writing audio");
          }
        }

This might have side-effects, I didn't notice any though. Take a look at the NAudio project.

Please use Build + Clean the next time you create an uploadable .zip of your project.