If you've exported a video for iPod play, you may come across a situation in which the converted video doesn't contain any sound when you play the file in QuickTime Player, iTunes, or on your iPod. If this is the case, the original video file may be in a format that contains muxed (multiplexed) audio and video, and cannot be exported with audio.
To determine if your movie file is muxed, follow these steps:
- Open the original movie file in QuickTime Player.
- Choose Window > Show Movie Inspector.
- Note the entry next to Format.
If the format is "MPEG1 Muxed" or "MPEG2 Muxed," the audio portion of the file may not be retained with QuickTime Pro or iMovie. Please see this article for more information.
See these documents for more information: