I have a few .mp4 source files that I'd like to combine into a single file. I've done the editing and exported. When played, the audio is misaligned to the video. As a test, I've tried exporting a single clip rather than joining a few and the same thing happens. I end up with audio that is misaligned to the video after export even though they are perfectly synched in the source video. As another test I've tried exporting a single clip to .mpeg rather than .mp4 and the audio stays perfectly synched with the video. It seems the misalignment occurs whenever I export to .mp4. I'm obviously missing a fundemental concept here. Can anyone shed some light on it for me? Thanks in advance.