devkitPro

I want to swap between TVNtsc480IntDf and TVNtsc480Prog (480p) but I want to do it by changing the VI registers manually. I have looked at YAGCD and there is a VI clock select register (0xCC00206C) two swap between 27mhz and 54mhz do I need to change any other registers to get 480p to work?

You need to change quite a few other registers, mainly the ones that control vertical timings for both fields.