So do you have a connection to TuneFab Comverter?If TIVO supports iTunes M4V videos, you are able to stream those videos on TIVO directly. If not, you can get helps from some video converters like Handbrake, Format Factory, TuneFab M4V Converter, which can convert m4v to mp4, especially the last one, it is designed for converting m4v to mp4.
Second this. The videos that itunes provides for download are often of lower quality than what is available for streaming (720p vs. 1080p). I haven't done a direct comparison between Vudu streaming vs. Itunes downloads, but I'd assume that it is of higher quality than the downrezed itunes downloads.An alternative, legal, way... sign up for a Movies Anywhere account, link it to both iTunes and Vudu, use Vidu app on TiVo to watch movies. (also works with Amazon instead of Vudu)