Android: testing device testing

I am working on applications that play audio and video as main UI elements. Something I notice is that across a wide range of Android devices on the market, playback will or won't work differently. The system often behaves as if the playback completed successfully (callbacks, not an error), even if the user only heard part of the sound, or some parts do not play correctly.

I have a good emulation environment set up to run Unit Tests on different devices, however I don't have good methods to test the actual output / input to the system during these events.

Are there any methods to unit test and make sure audio or video is playing on those devices (i.e. the audio produced?)?