I'm having a problem whenever I try to convert to MP4 on my MAC. I've done it from within FFMPEG and also from within Tivo tool using the FFMEG conversion engine. It seems to run fine but when I try to play the resulting video file the system tells me that it's not a valid video file. When I try to open it using VLC it tells me that MP4 discarded (no moov box)

Any help would really be appreciated.