Causes for audio/video out of sync

[mridang_agarwal]

what the cause for audio/video becoming out of sync with each other. I've see that people face this problem while trying to demux/remux files? If you demux a file and you face sync problems while remuxing the streams, what could you do to correct this? Lets say, you were faced with the problem of the audio lagging behind the video by a few seconds, what would you do?

[Baldrick]

You can cut or add silence at the beginning of the audio, in for example goldwave. Then remux it with the video. This will only work if the audio is same out sync the entire clip.

And I wouldn't say that demuxing and remuxing cause most problems, it mostly when you are converting from downloaded crappy video to another format or capturing video.

[dphirschler]

I deal with two different problems in two different ways.

Constant
If the audio is out of sync and remains constant, then it is just a matter of moving the audio forward or backward in time. You do that in many different ways. You can add a frame or two to your video and re-encode. Or you can add to or cut from your wav file. Or you can adjust the audio delay by changing a number in your authoring package.

Drifting
If the audio drifts out of sync, then you have to study the video. Watch it and try to determine if it is slowly difting of if there is a moment where it suddenly becomes out of sync.

If it slowly drifts, you have to look back at what you did. For me, it will have to do with some sort of conversion I am doing and I probably got the frame rate wrong. In that case, I have to get the frame rate right. If it is a PAL/NTSC conversion, then I have to make sure I converted the audio in Besweet.

If it suddenly goes out of sync, then look for dropped frames in your video. You may need to deal with that by adding in frames or recapturing that section. Hopefully your capture software gave you a log of where the dropped frames occured.

Hope that helps.


Darryl