title: GetSampleAsync does not fire in MediaStreamSource on WP7 device
body: <p>I've been developing an audio app for Windows Phone 7 and up to this point have been using the WP7 emulator. The app uses a custom MediaStreamSource class to stream audio to a MediaElement.</p>
  
  <p>On a real device, the custom MediaStreamSource completely fails. After calling MediaElement.Play(), the MediaStreamSource's GetSampleAsync method never gets called. It works just fine in the emulator.</p>
  
  <p>I've started the app in the debugger (running on the device) and no exceptions get thrown anywhere.</p>
  
  <p>I'm wondering if maybe my stream source is using a sample rate, bits per sample, or channel count that is not supported? I cannot find any documentation on what values <em>are</em> supported - however I find it hard to believe that my settings are not supported (44,100 Hz, 16 bits/sample, 2 channels).</p>
  
  <p>Thoughts?</p>