Mpeg multiplexed (Muxed) files have the video and sound combined in one stream. QT does not by itself demux such files and will only export the video portion. To preserve the sound you will have to find (on VersionTracker) a freeware program called BBDemux. While there, also find another freeware program called SoundApp. Run BBDemux. You will wind up with two files; a video file with a m1v extension and a sound file with an m1a extension. Use SoundApp to convert the sound file to AIFF. Open both this file and the video file in Quicktime, copy the sound data to the clipboard, switch to the video file document, be sure the time slider is at the far left, and then use Add Scaled from the Edit menu to add the sound to the video. You now will be able to export both sound and video to the formats of your choice. If you are going to edit and recode in another application you should use a lossless video compressor such as component video, none, or animation for the video compressor. If file size is a factor you can also try MotionJPEG A set for 100% and single field.