If you remember, last time I posted something like this it was a hoax, but believe it or not, it is being done. The people behind DivX for pc have began working and looking into porting DivX to the Dreamcast. Those of you who do not think the Dreamcast is powerful enough just look at Bleem!Cast, it is / was very powerful and could do anything that was needed to perfectly emulate the system. This to say, if divx was coded as well as Bleem!Cast was then it could be perfectly possible.

Check out this post on there forums for there details and possible aid in there development:
http://forums.projectmayo.com/viewtopic.php?topic=3119&forum=23

*Update*
After reading up on the post’s, it seems they have gotten DivX to work on the Dreamcast and its running pretty fast, most of it is coded and progress is being made. I am talking with the authors and trying the best I can to help them get the information they need.