How to fix AVI files with audio and video out of sync

If you've ever experienced audio video out of sync problems where the audio / video syncronisation is fine at the beginning, then becomes so out of sync by the end of the movie that it's unwatchable. Then you are right here. In this article we are going to cover this and aim to find a solution to fix the audio video sync problem.

Often due to a badly prepared file (different length for video and audio streams, for example). This problem can be worked-around with software players or fixed permanently in cases.

VirtualDub

This should work on any file that can be opened with VirtualDub.
1. Determine "exactly" what the frame rate is on the problematic movie with Cliprex Video Properties or with some video player like DivX Player.
2. Open Virtual Dub, under "File", click "Open video file..."
3. Click "Video", "Direct stream copy"

4. Click "Video", "Frame rate..."
5. Click the radio button beside "Change to _ frames per second"
6. Enter a number in the box that is about 0.002 slower than determined in step 1
7. Click "OK"
8. Click "File", "Save as AVI…"

AVI Frame Rate Changer

Instead of using VDub, which need to re-save the file, use AVI Frame Rate Changer, which just patch the .avi header without re-saving.

AVI Frame Rate changer allows you to modify the frame rate of a pre-rendered AVI File without re-rendering the AVI data. Full Delphi source code is included. Please note that it may not work well with certain AVI files and you may want to keep a backup copy of the modified AVI file (just in case).

You just have to change the value, click OK and test.

Conclusion

You may have noticed that both tools are for you to change the frame rate to sync video and audio. So if you have encountered any playback issues after conversion with iSkysoft Video Converter, you can go back to change the frame rate and convert again.

In a 2 hour movie, decreasing the frame rate by 0.002 will move the video 0.5 seconds behind the audio by the end of the movie.

Now open the new AVI and see if the audio video sync problem is corrected. If the audio is still lagging behind the video go back and further decrease the frame rate.