I snagged some movies (mp4) that are supposedly high def. They look great on the PC. Pulled them to the HD tivo using pytivo. On the HD tv they look very choppy; unwatchable. On the much smaller non-HD tv they look fine (with S2 tivo). File size is about 800mb per hour. I have other videos that were rips of standard dvds (i ripped them), they always looked fine on the HD tv. File size about 400 mb/hour. Ideas?