AV Sync Fix allows you to adjust out of sync audio/video movie files.
It does not edit actual encoded media sample data. It edits time-mappings. You can immediately see the effect of the adjustments and overwrite it without loss of audio/video quality. It's very fast. There is no need to export a modified movie file.
When you open a movie file, the app copies it to the storage of your Mac as a temporary file for editing. The app needs available storage size more than twice as much as the file size. Copying may take a few minutes depending on the file size. The temporary file will be deleted when you close the main window or quit the app.
・QuickTime movie (mov)
・MP4 file (mp4, m4v)
(Except DRM protected movies)
AV Sync Fix cannot open files which require any conversion or codec components in QuickTime Player. Or nothing will be displayed.
Ratings and Reviews
Works great once you figure it out
No documentation to speak of and so figuring out how to use it can take a bit of time. I tried a couple of things and one of them worked and voila - my video was fixed. Would be five stars with proper documentation.
In my case I saw the audio and video tracks had different lengths - I subbtracted these and set the audio to start at the difference, and that did the trick.
With Family Sharing set up, up to six family members can use this app.