AV Sync Fix
Current Version 2.56
What is AV Sync Fix
AV Sync Fix helps you correct audio and video that are out of sync in video files (MOV, M4V, MP4). You can adjust synchronization easily by dragging on the timeline, or more precisely by entering values.
The app fine-tunes playback information—such as media start time and duration—to bring audio and video back in sync. When saving, no re-encoding is performed. Only playback information is updated, so there is no loss in video or audio quality, and even long videos are processed quickly and smoothly.
NOTE!
- When you open a video file, the app creates a temporary working copy of the original. The app requires free storage space of more than twice the file size. Copying may take some time for large files, but it enables efficient adjustments and instant preview of results. The temporary copy is automatically deleted when the main window is closed or when you quit the app.
- Please make sure to back up your files before using this app, just in case an unexpected error occurs.
Supported formats
- QuickTime Movie (.mov)
- MP4 file (.mp4, .m4v)
But the app cannot open/play the following files.
- Files that QuickTime Player cannot open
- Files that require conversion or additional codec components to open in QuickTime Player
- DRM-protected files such as movies or TV shows downloaded from the iTunes Store or TV app
- Fragmented MP4
System Requirements
macOS X 12 or later
Version History
- 2.56 : 2025-10-17
- Fixed an issue where edits to the file playback duration might not be reflected in the saved file
- Fixed some other bugs
- Performance improvements
- 2.55 : 2024-03-11
- Fixed an issue where the markers on timeline are not displayed
- Fixed some small bugs
- 2.54 : 2024-03-06
- Fixed the cluttered UI on macOS 14 or later
- 2.53 : 2024-01-16
- Usability improvements
- Fixed some bugs
- 2.52 : 2022-12-06
- Fixed some bugs
- 2.51 : 2022-11-23
- Usability improvements
- Fixed some bugs
- 2.50 : 2022-07-01
- Performance improvements
- Fixed some bugs
- 2.4 : 2021-10-25
- Added support for loop playing
- Added support for playing a selection
- Fixed some small bugs
- 2.3 : 2021-09-08
- Usability improvements
- Fixed an issue that may cause problems with dragging the timeline
- 2.2 : 2021-08-24
- Fixed an issue where dragging a video track in the timeline may cause rotate the video frame
- 2.1 : 2021-08-20
- Universal Binary
- Added support for displaying sound waveform
- Added support for editing by dragging timeline
- Added support for dividing, merging and deleting track-segments
- Added support for changing skip time amount
- Added support for Time Bar Preview
- Fixed an issue where a crash occurs when opening files which contain incompatible media
- 2.0 : 2020-07-25
- Reverse play supported
- Added keyboard shortcuts to change play speed
J: Speed down
K: Normal speed
L: Speed up
M: Reverse play - Fixed small bugs
- 1.9 : 2019-10-17
- Optimized for macOS 10.15 Catalina
- Internal code improvements
- 1.8 : 2019-08-24
- Stability improvements
- 1.7 : 2019-02-21
- Fixed an issue where crash may occur when opening protected contents
- Updated supported format
- Stability improvements
- 1.6 : 2018-10-11
- Optimized for macOS 10.14 Mojave
- Added support for dark mode in Mojave
- Fixed small bugs
- 1.5 : 2018-04-25
- Fixed an issue where no sound comes out in some videos
- Fixed other small bugs
- 1.4 : 2016-10-27
- Optimized for macOS 10.12
- Fixed an unexpected result when editing media time value with specific files
- 1.3 : 2016-02-28
- Fixed several minor bugs
- 1.2 : 2015-05-02
- Fixes an issue where the app is crashed when doing play/pause in OS X 10.10.3
- 1.1 : 2015-03-31
- Fixes an issue where a crash occurs when closing a window during loading a file
- 1.0 : 2015-02-25
- Released
