Crash in WasapiCapture when device is unplugged

I have implemented something similar to “How to record and play audio at the same time with NAudio”, but using a USB audio device, WasapiCapture and IWaveProvider. Everything works correctly until I unplug the device.

When the device is unplugged, an exception seems to be thrown in the capture thread of WasapiCapture, here’s the stack trace :

System.IO.FileNotFoundException
  HResult=0x80070015
  Message=Non implémenté

Non implémenté

  Source=NAudio.Wasapi
  StackTrace:
   at NAudio.CoreAudioApi.Interfaces.IAudioClient.Stop()
   at NAudio.CoreAudioApi.AudioClient.Stop()
   at NAudio.CoreAudioApi.WasapiCapture.CaptureThread(AudioClient client)
   at NAudio.CoreAudioApi.WasapiCapture.<StartRecording>b__35_0()
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
--- End of stack trace from previous location ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

(Non implémenté means Not implemented)

It looks like the call to client.stop() in the finally block of CaptureThread fails, and I cannot catch the exception.

[JacqiPan]

After some debugging, I don’t think it has to do with the client being null. If I make something like this :

Since AudioClient is a COM object, it simply loses its reference as soon as it’s unplugged. So it’s not technically null, as stated above (“null”), and will always throw an exception when you try to access it after the endpoint device disconnects,. The try-catch solution works, since it catches the exception for AudioClient just like it did within DoRecording()

I could do some dubious things to get the audioClient private variable and check if it’s null, but I don’t think it’s a good solution.

It is already available within the MMDevice class, which can be accessed through a MMDeviceEnumerator. If you use WasapiCapture without specifying an MMDevice, it will just use your Windows default audio device MMDeviceEnumerator.GetDefaultAudioEndpoint(DataFlow dataFlow, Role role)

I used something like this:

 private void OnDataAvailable(object sender, WaveInEventArgs waveInEventArgs)
    {
            try
            {
                if (CaptureMMDevice.AudioClient != null) // Will throw as soon as the device is unplugged
                    bufferedWaveProvider.AddSamples(waveInEventArgs.Buffer,0, waveInEventArgs.BytesRecorded);
            }
	    catch
            {		
                WasapiCaptureClient.Stop();
                WasapiCaptureClient -= OnDataAvailable;			
	    }		
    }

[loics2]

Oh I wasn’t aware the audio client was accessible from the MMDevice, and I store it in a variable somewhere. It works correctly, thanks!