I was holding off because of being busy and hoping someone would post the right info - here's a swag, best I can do...
When we talk about media formats, it really means the container (file) type and the video and audio codecs contained).
Here's a list of codecs supported in Android -
Android Supported Media Formats | Android Developers
Problem with that list is that I don't believe it's complete - the core codec package changed for 2.2 - and I'm not clear where an official list is.
When all else fails - H.264 works. I have .mpg files on my phone that use that codec and play just fine. I recall that somewhere around 2.0 or 2.1 they broke support for MPEG-2 (I _think_).
I use this to convert vids, there are plenty of others and most folks hereabouts use handbrake - I'm just putting this out there because it works for me, I've used it for years - just in case you need a converter -
Squared 5 - MPEG Streamclip video converter for Mac and Windows
PS - also make sure you've got a good player - I use Meridian, others really like RockPlayer - sometimes a player can add codec support.
If you can examine the mpg file on your PC with QuickTime or maybe VLC, you can find out what codec it is and see if you find a player with that for Android.
I found a plays-nearly-anything player for Android - and naturally spaced bookmarking it or downloading it at the time.
