Hey, I am Ben Waggoner :).
Anyway, a few comments on IPTV/DBS style broadcasting. All the standard def digital cable and digital satellite today in the US uses "Half D1" which is 352x480 interlaced 29.97 fps. So there are actually quite a fewer pixels per second to process than with 640x480.
Also, today broadcasting uses statistical multiplexing, where they're doing a VBR across multiple simultaneous channels. So even if a channel averages 1 Mbps, it'll go up and down quite a lot during the connection.