Hi;
Standart Definition (SD) CVBS signal occupy around 8Mhz bandwidth. So considering Nyquist criteria you should at least put 16Msampes/sec. And it is generally advised to do 2xover sampling to make filtering easier and better video quality. Have a look at these also; https://www.analog.com/static/imported-files/application_notes/7378546AN_944.pdf
Book: Keith, Jack. 2005. Video Demystified
I think ARM speed should be enough.
By the way how do you plan to generate video, you read video files from USB or smthng like that?
Actaully i have not much experience on video formats and decoding.:sad: For baseband video i have some info.
But i think you will need an MPEG decoder on arm at the end. I am not sure how it is possible decoding MPEG using only sw staff without any dedicated hw block.
Some experts should comment on it.