Not all file formats support multi channel audio, or work with it equally well. We found it easiest to work with raw wave files (for great support with Audacity, e.g.) or AAC.

Usually very straightforward, ffmpeg picks the output format using the file extension. Wave to mp3, 5 seconds only, 128kb/s, is:

FFMPEG is a great tool for doing anything programmatically with audio or video files, but the default installation contains only open standards, and is therefore utterly incapable of converting AAC files and other common standards. Time to build it ourselves!

Important: make mMediaPlayer a field, because otherwise the garbage collector will clean up the mediaplayer while the sound is still playing, causing it to be cut off!