MP4 audio (M4A or AAC) is more immune to accumulated damage than MP3. That’s a constant delay so it can be fixed and it doesn’t get worse with longer files. If you must use lossy compression MP3 will add a few milliseconds of silence to the beginning of the file so you may have to slightly re-adjust the timing after loading the audio into your video editor. I have a program called Womble MPEG Video Wizard that has a “fix timestamps” feature (which sometimes works), but I think it’s no longer available, it’s not free, and it might only work with MPEG-2.īTW - It’s best if you can export to WAV (or another lossless format) to minimize the number of times the audio is lossy-compressed. But, that’s a lossy process even at a higher bitrate. Sometimes, I’ve solved it by transcoding the original audio/video file to a different (usually slightly higher) bitrate or to a completely different format. It seems to happen more often with MPEG-4 or MOV files than with MPEG-2, and DV-AVI seems to be pretty-much immune. The more compressed files seem to be more prone to this. I think the problem is “timing glitches” in the original MP4.

How to export mp4 in imovie