How to Fix Out of Sync Audio/Video in an MKV, MP4 or AVI

This step by step guide will show you how to fix out of sync audio and video in a video file.

There are two ways to fix out of sync audio and video – one is temporary and quick, the other is permanent and a bit more involved, although still quite easy.

Temporarily Fix Out of Sync Audio and Video

The quick solution is to use the amazing (and free) media player – VLC, and its easy to use built in audio delay/forward feature. If you aren’t using VLC yet, head over to their download page and give it an install. Note: this will work for all video formats, not just mkv/mp4/avi – they’re just common formats (and the 3 that I’ve found most often have sync issues).

  1. Open the video with the out of sync audio in VLC and then select Tools -> Track Synchronization (Mac users: select Window -> Track Synchronization)
  2. the vlc tools menu

  3. Locate the section titled Audio/Video – within that window there’s a ‘timer’ with “up and down arrows” to adjust the timing of the audio. This is where the magic happens.
  4. the vlc adjustments and effects synchronization screen

  5. Use the “up arrow” if the audio is ahead of the video. That means if the people in the video are talking and you can hear them before their lips move, you’ll want to use the up arrow. That will ‘delay’ the audio, allowing the video to ‘catch up’.

    So in reverse, if the audio is behind the video you’ll want to use the “down arrow”. That will speed the audio up.

    In both instances, when you use the up and down arrows it will adjust your audio by 1/10th of a second per click. Let the video play while you’re making the adjustments – but note that it’ll take a second or three for the change to take place each time you adjust the sync timing.

  6. the vlc adjustments and effects synchronization screen with adjusted audio timing

Permanently Fix Out of Sync Audio and Video

To permanently fix out of sync audio and video, you’ll need to download an open source (free) video editor, Avidemux. It’s cross-platform which means it’s available for Windows, macOS and Linux.

Note: the screenshots used below are from a Mac, but the steps and screens are nearly identical if you’re using Windows or Linux and you should have no trouble at all following along.

  1. Once you’ve downloaded and installed Avidemux, open it.
  2. the main avidemux window

  3. Select File -> Open…
  4. the open a file menu for avidemux

  5. Navigate to the video file that’s out of sync, select it and then click Open
  6. selecting a video in a file manager

  7. After a few moments the video will open up in Avidemux. Use the “timeline slider” (see screenshot below) to move the video forward a bit.
  8. a timeline slider button

  9. With the video paused, place a check in the box labelled Shift, which can be found in the Audio Output section.
  10. the shift box in the audio output section of avidemux

  11. Use the “up arrow” in the Audio Output section to increase the number of milliseconds if the audio is ahead of the video. That means if the people in the video are talking and you can hear them before their lips move, you’ll want to use the up arrow. That will ‘delay’ the audio, allowing the video to ‘catch up’.

    So in reverse, if the audio is behind the video you’ll want to use the “down arrow”. That will speed the audio up.

  12. the up and down arrows located in the audio output section

  13. Use the Play button to determine if the video is now in sync with the audio and keep adjusting with the up and down arrows until it is.
  14. a play button

  15. Once you’re happy with the result, select File and then Save
  16. a save as dialogue box

  17. Give the video a new/different name so that you don’t overwrite the original, which you can delete later once you’re sure the new video is perfect. Leave the video type as mkv and then click the Save button.
  18. a save button

  19. Give Avidemux a few moments to do its thing.
  20. fixing out of sync audio

  21. Ta-da! All done. Click the OK button and then exit out of Avidemux. Open your newly created video file in your player of choice and make sure it’s all synced up.
  22. a video file with the audio and video in sycn

Other Resources

How to Add Bookmarks to a Video
How to Extract Just the Audio from an MP4 File

8 thoughts on “How to Fix Out of Sync Audio/Video in an MKV, MP4 or AVI”

  1. Thanks for the info! However, I can’t figure out what the next step is, in order to save the video clip. I’m on a Mac. Any clues?

  2. It might not be a permanent solutions as others have mentioned, but at least I can watch my show without being completely annoyed!! Thank you ! :)

  3. My friend (lol) has just started to have the audio /video not syncing in anything he downloads or has previously downloaded and had been working fine.. tried swapping VLC to Pot Player to fix problem but didnt change anything.. can anyone help or have any idea what can be done to resolve this issue?

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