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I have a video which has various audio out of sync at different times. For example, from 2:00 to 4:30, the audio delay is 6 seconds, and 3:00 to 6:00, the audio delay is 8 seconds & 38 min ti 42 min audio delay is 2 sec.

How can I fix this part-by-part without cutting the video? The video is 42:00 min long, where the same type of problem occurs many times.

I'm using Windows 7 32 bit, playing with VLC. The problem occurs the first time. Other videos play well. The video is delayed not constantly, it differ min to min.

it quite tough to cut audio without see video and set delay

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    You're going to have to extract the audio file and then cut it manually using Audacity or similar. Then, merge the audio file back in. Does that sound like a doable approach? Will you be able to edit the audio without looking at the video?
    – slhck
    Jun 28, 2012 at 12:43
  • You can actually also write replies here … just press the "add comment" button. I'm not going to check this question forever and I won't get a notification if you edit your post. Well, if you can't edit the audio separately, then load the video in some video cutting software and just do it. You don't have any other choice.
    – slhck
    Jun 28, 2012 at 12:52
  • what @slhck said x10, but it's going to be a pain in the behind. Where did you get the video, was it converted from a larger source? Can you get the source footage? Can you get a different copy of the video? If the sound is actually in sync at any point AFTER one of those times it is out of sync, then the total length of the audio track is correct, which will make editing the parts that are OOS even harder.
    – Bon Gart
    Jun 28, 2012 at 13:11
  • wait... I just re-read what you said. "The video is delayed not constantly, it differ min to min." so, the delays you listed won't be the same the next time you play it? What is a 6 second delay between 2 and 4 minutes won't be a 6 second delay in the same spot the next play-through?
    – Bon Gart
    Jun 28, 2012 at 13:13
  • @BonGart Or... The audio even speeds up and slows down. Which would be even worse.
    – slhck
    Jun 28, 2012 at 13:18

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This problem can be caused by an incorrect conversion of an MPEG2 stream. MPEG2 streams do not have a fixed framerate; each frame is timestamped. But when converting to formats that require a fixed video framerate, most software simply assumes that the frames come at regular intervals. So if the source video has random timing breaks within the video stream here and there (not uncommon with video capture cards), the converted file will have different audio offsets at different places, just like you describe.

If this is indeed the problem in your case then the fix is quite complicated. ResyncMpeg2Audio can be used to analyze the video timing and generate an avisynth script that automatically repositions the audio to match the now-fixed framerate. Be aware that it is a pretty arcane procedure (described in detail on the project's wiki).

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