If you created the mp4 using quicktime, you can load it into quicktime and then select save as self-contained movie, and you will end up with a mov version in seconds, as no reencoding is required.
Converting the other way round, from a mpeg4 .mov to a .mp4, is easy and fast using quicktime pro. Open the mov and select 'export movie to mpeg4, but select 'pass-through' as the video and audio type. This will make a mp4 file from a mov without recompressing, and so is very fast.
Tuesday, December 06, 2005
MPEG4 to MOV
Steve Watkins writes on the Yahoo! Videoblogging Group list: