Hmm, noticed broadcom introduced the "B" version of the 7400. Wonder which one is inside the 722. Seems like the B adds a few codecs, although the old 7400 already supported VC-1 like Smith said.
http://www.broadcom.com/press/release.php?id=970100
The new chip runs Java OCAP extensions -- the only other substantive difference is transfer to a 65nm line which will mean less heat from the chip; so less cooling. The OCAP add-on makes the chip appropriate for the next generation of Open CAble Platform set top boxes.
Cheers,