Could you point me to a .tivo file you think is representative ? Basically, if ffmpeg or mplayer (the www.mplayerhq.hu one, not the windows media player) can read it, you should be OK.

Also, don't worry about the linux thing. I managed to dig up an old copy of XP that came with my laptop which I can use in an emulator - and that should be enough for at least the packaging part. So that's linux+windows support at release. Mac packaging volunteers needed !