800 * 480 * 16bit * 30fps = 23million bytes written out to the screen per second. Don't even look at higher resolutions, it's literally exponential in bandwidth. Video takes a lot of data. The highest resolutions and framerates put the fastest network speeds to shame.
A CPU just plain can't do this. Even if you want to pretend it's one cycle per pixel the realtime constraints at higher resolutions are way out of the realm of feasible. We struggle to do CPU driven audio in realtime as-is (Audio is measured in Khz of bandwidth rather than Mhz).
You can do this at very low resolutions easily enough (again it's exponential with resolution increase) but then you have a low resolution screen.
A CPU just plain can't do this. Even if you want to pretend it's one cycle per pixel the realtime constraints at higher resolutions are way out of the realm of feasible. We struggle to do CPU driven audio in realtime as-is (Audio is measured in Khz of bandwidth rather than Mhz).
You can do this at very low resolutions easily enough (again it's exponential with resolution increase) but then you have a low resolution screen.