it should be easy to install the support for mp4 and m4v into the Moodle Multimedia Filter. Both formats could be played with QuickTime on Mac OS X and Windows XP/Vista. I met Martin at the MoodleMoot 2009 in Bamberg/Germany and he fixed the problem for mp4 on my own MacBook.
It would be good if the coding will be implemented into the official Moodle 1.9.5. YouTube started to use mp4. The video iPods are using mp4 and m4v.
Best regards, Ralf