Formula for Audio Streaming in mobile devices?

I wonder what would be a good formula to calculate how many byte开发者_高级运维s I have to download for smooth playback.

I have the file size before start to download and I can check the network (GPRS,EDGE,UMTS...). I know that there are so many possibilities (network delay, network changes, no network...) I appreciate any good read about it.

Thanks :-)

I think this is a good approach: Smart progress bar ETA computation