cjdelphi:
I thought I'd do quick search on the rgb / ntsc chip...
http://belogic.com/uzebox/index.asp
It seems there's quite a lot going on!
Uzebox is an impressive feat indeed, but they also use a more powerful microcontroller with double amount of RAM and ROM, and almost twice the clock frequency. My project was based on Arduino UNO. We both use the same AD725 chip for RGB -> NTSC though.