Digitize RGB video using DE0-Nano

I dont really like the way you've done your frame buffer - I dont see this actually inferring a ram because of your unregistered read and write addresses (not to mention potential poor timing performance, but at 25MHz you can probably get away with it).

As for the jitter, rather than syncing the input to the output you might be better off just free running the output and inputs and using the frame buffer in the middle to get the data accross. You might get the odd tearing frame but to mitigate you should be able to make the output repeat a frame if the output catches the input.