I can confirm that mp4 container with h.264 video + ac3 audio works fine as well as long as you use pyTivo as the video server. Tivo Desktop doesn't allow it probably because the codecs it's using don't support it. Dan, one can use ffmpeg to generate such a video so handbrake is not the only option. The key is the moov atom must be at front of file for it to work, so if that's not the case then you can run qt-faststart on the file. And yes unfortunately the pushes still make the mp4 files on the Tivo copy protected so you can't transfer off the Tivos.