How do I fix audio sync in AVI file ? I have AVI video file, audio is out of sync about 6 seconds. How to synchronize audio and video streams? Thanks.
Download the latest version of AVI audio sync tool:

First of all, make a backup copy of your avi file (this is very important!).

Step 1. Unzip file. Launch YAAI.exe , "open avi" dialog will appear.

Step 2. Find and open your AVI file.

Step 3. Click on "Sync Audio" tab. Small video player will pop up.

Step 4. Now, adjust audio delay or frame rate (FPS) using sliders or appropriate buttons.

Click Apply. Video player will start playing your file with changed settings automatically. You can adjust and apply these parameters several times to pick up necessary values for audio delay or FPS. So, try to experiment and to set appropriate audio delay or to change FPS (frames per second) settings for your avi file.

Step 5. Finally, close YAAI tool. When it asks the question: "Do you want to keep the changes?", click Yes.

You AVI file will be corrected instantly.

Users reported that YAAI does not work with certain avi files. So, here are alternative solutions:

Situation 1: Constant loss of audio/video synchronization in AVI (throughout the video file).

Step 1. Download AviMUX: Click here to download AviMUX

Step 2. Unzip it into separate folder, and launch AVIMux_GUI.exe

Step 3. Load your avi file into Avi_mux (right-click -> add). Click on the avi file to select it.

Step 4. Click the "Generate Data Source From Files" button. Information about audio and video streams will appear in the bottom window.

Step 5. Click on the audio stream. Now, you must see "delay [ms]" showing on the right side of the window.

Step 6. Enter audio delay value, for example:

If you see in the movie that a person speaks, and you can hear the voice only several seconds later (Audio is after Video), then you must choose negative value (in milliseconds), for example:
-5000 = shift audio by 5 seconds before video

If you can hear the voice in the movie too early, and only after several seconds you can see & determine who has said that (Audio is before Video), then you must enter positive value (in milliseconds):
5000 = shift audio by 5 seconds after video

Step 6. Finally, click start button, choose output avi filename. DONE!

Situation 2: Gradual loss of video/audio synchronization in AVI (everything is normal at the beginning of the video file, but audio is gradually shifting during playback)

In this case you must adjust FPS (Frame per second) of the avi file. After that, audio and video will be synchronized throughout the movie. But how to determine exact FPS you need to fix gradual loss of synchronization?

First of all, you must launch your movie in any video player (Vidmex is recommended). Go to the end of your video file (5-10 minutes before the end of the movie), and observe the difference between video and audio -- you must determine:approximate value of the delay in seconds and type of the delay - "Audio is before Video" or "Audio is after Video".

Now, download a special program AVI FPS Changer, called AVI Frame Rate Adjust: Download AVI Frame Rate Adjust.

Unzip it, and launch FrateAdj.exe. Make sure you have a backup copy of your AVI file. Click Open, find and open the avi file.

Ok. AVI file is opened inside the program. Here you can see information about the file. In this case, we need only fps and Length values. Write down/remember the original Length of the video (for example, 2:22:12).

Try to change fps value. You must perform MINIMAL adjustments. For example, if you have 25fps then you can try 25.004 , 25.008 or 24.998 , 24.990 values etc. Notice, every time when you change fps, Length is also changing.

Now we must consider how to change FPS according to type of the delay:
- if Audio is before Video at the end of the file, then you must increase FPS;
- if Audio is after Video at the end of the file, then you must decrease FPS;

After you have experimented and finally changed fps, the difference between original Length and actual Length must be equal to the value of the delay at the end of the file.

For example,
if "Audio is before Video" and delay is 2 seconds at the end of the movie, then we must experiment with increasing FPS, and to choose 25.005 (actual Length of video will be 2:22:10, original length was 2:22:12).
if "Audio is after Video" and delay is 2 seconds at the end of the movie, then we must experiment with decreasing FPS, and to choose 24.995 (actual Length of video will be 2:22:14, original length was 2:22:12)

Finally click Save button. You AVI file will be saved with new FPS value and the gradual loss of video/audio synchronization will be fixed.

TIP: If you receive this message: "Error opening avi!" when you try to save file, then you must change avi file attributes. Download Attribute Changer, install it. Next, open explorer. Go to My Computer, and find your avi file. Right-click on avi file, and choose "Change Attributes..." from the drop-down menu. Uncheck "Read-Only" and uncheck "System". Leave only "Archive" attribute. Done! Now you can fix audio sync, and save changes to this file.

Another alternative approach to change framerate (FPS): free AVIFrate program.

Click here to download AVIFrate

AVIFrate is an utility that allows you to change many important fields in an avi file header. Most often you need to adjust the frame rate of the avi video stream.

The frame rate is determined when you play a file by simple formula:


where fps is "frames per second" playback speed, dwRate and dwScale are fields of the video stream header.

After you change these values, AVIFrate will re-calculate frame rate and will allow you to write it directly into the file header. You can undo changes made until you exit AviFrate. This allows you to try out some values before you decide to keep them.
 See Also:

 How to repair, fix MPEG video file ?

 How to repair, fix ASF file ?

 How to repair, fix AVI file ?

 How to repair, fix MP3 files ?