Amplifying playback volume from a local AMR file

I have an a开发者_运维百科pplication that plays back AMR audio files that it has downloaded and cached locally.

This works fine — the basic MediaPlayer does its job.

However, the audio volume is generally very low, and manually increasing the volume with the hardware keys still doesn't make the playback quite loud enough.

The behaviour seems to vary across devices — Sony Ericssons are particularly low, HTC devices are reasonable, and the Samsung Galaxy S is actually very loud when the volume is turned up to the maximum.

Are there any relatively simple approaches, using the Android SDK, that could, say, double the volume while playing back from the AMR file?

I note that AudioTrack allows you to manipulate audio, but this seems to be for raw PCM streams.