From Noah Sorscher:
Sync-Hole allows you to get the audio and video of QuickTime movies in sync with each other.
Where Sync-Hole excels is with movies that drift in and out of sync, for example if it is in sync at the beginning and end, but not in the middle. Sync-Hole can stretch parts of the video track to realign with the audio, while keeping other parts of the movie exactly where they were.
Sync-Hole can also do the simple manipulations that are available from other programs, such as stretch the video track as a whole, or simply slide the audio track back and forth ("offset").
Sync-Hole cannot access any movies that QuickTime cannot. For example, if a movie can't be opened in QuickTime, it can't be opened in Sync-Hole either, and if it can't be edited in QuickTime Pro, it can't be edited by Sync-Hole either (this mainly applies to MPEG-1 and MPEG-2 movies).
To use it, just open a movie, play it until you detect an asynchronism, then tell the app wether you think the video or the audio is ahead, and by how much. Sync-Hole adjusts either the audio offset or the video framerate to compensate. Then you set an "anchor" before and after the scene that is synchronized, and move on. Sync-Hole only changes the framerate in between anchors. It is basically a fancy wrapper for the Quicktime Framework function, ScaleTrackSegment. It also allows you to jump forward or back by a certain distance, or to jump to the spot half-way between the two most distant "anchors," to facilitate finding out of sync scenes.
This review was originally posted on VersionTracker.com. What an amazing application. I've had poorly synced movies I've lived with for ages in the hopes that one day I could repair them. And then something this elegant comes along. Tiny but totally effective. I love it!