Portable DVD players w/ MPEG4?

[DarkMatter]

I'm looking for a portable LCD DVD player. I see some list that they are MPEG4 compatible. What, exactly, does that mean? If I just drop .avi's (Xvid, DivX, etc.) onto a DVD-R will the files play or do I need to format the disc somehow? The players specifically list MPEG4 not DivX so I assume they mean .avi files.

Any help appreciated.