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Thread: Help With Audio Sync

  1. #1
    Hello everyone, Ive been searching the web for a few days now and i havent been able to find a solution to this problem and i was wondering if anyone here can help. I have some avi movies that I am reencoding to reduce the file size and some of the movies come out great. But the ones with framerates of 23.976 wind up like this. The audio is in sync at the start of the movie and gradually goes out of sync so that by the end of the movie the audio is around 5 seconds out of sync. I have tried every encoding option in DivX with the same results and Im really at a loss as to how to reencode these movies without the sync problem. If anyone can help or point me to a guide I would sure appreciate it. Thanks in advance.

  2. Movies & TV   -   #2
    This is a common problem that has been discussed at great length with little success at the Vdub forum. The only halfway workable solutions I ciyld find are when convertring MPEG-2 files: (1) Don't touch the audio rate- select straight copy, and (2) set the frame rate to 30,0 There were some other possible solutions listed. I think all you need do is a global search for "audio sync."

  3. Movies & TV   -   #3
    Thanks, I didnt realize there was a search function here till I looked a little harder I'll go look.

  4. Movies & TV   -   #4
    if the original files use VBR audio, they will go out of sync when you encode them.

    this warning is told to you when you load one of these files onto VirtualDub.

    you have to extract the audio from the avi and use it seperatly.

  5. Movies & TV   -   #5
    Join Date
    Mar 2003
    U could also tri a few different versions of vdub...some a just no good ,crap.

    myself i find the 1.4 mod the best one.

  6. Movies & TV   -   #6
    I had one file that used VBR audio so I extracted the audio to wav and recompressed it into the video stream. I dont think I had any problems reencoding that file though.

    One thing I just noticed is when I extract a .wav file from one of the movies that goes out of sync when i reencode, the actual .wav file is 5 seconds longer than the movie after the movie is reencoded with no sound. I have no clue why this is either.

  7. Movies & TV   -   #7
    Join Date
    May 2003
    you can also set the duration of your audio file using an audio editor software.
    i would recommend Sound Forge 5.

    best of all, you can use it for free! just crack it!

  8. Movies & TV   -   #8
    well im starting to see what is happening. When I reencode the files Divx drops some of the frames. And I think these are extra frames from deinterlacing or interlacing or something like that and they get dropped out throughout the whole movie. This is why the resulting movie is shorter. I tried using cool edit to shorten the .wav file and add it back in but that doesnt work either because the lost frames are all through the movie and even though the audio and video are now the same length they wont stay in sync. There has to be a way to reencode the video without losing any frames. Then the audio will stay in sync. If anyone knows how to do this please post

  9. Movies & TV   -   #9
    I wanted to add an update to this post for anyone who read it before. The audio sync problems I was having didnt come from any particular frame rate. What I learned was...

    1. Sometimes divx will remove frames that are doubled or tripled in a movie file. One file I worked on I found divx had removed 117 redundant frames saving some files space but also causing the audio to be about 5 seconds out of sync. To get the audio back in sync I had to seperate the audio with virtual dub and then locate the spots in the movie where the frames were removed, there were 4 spots. I found these spots by comparing the original file with the one I was reducing narrowing the spots down by where the movie went out of sync. Then I edited the .wav file in each spot where frames were removed by shrinking that period of time in the wav to bring it back in sync. Like this, if 48 frames were removed and the frame rate was 25 fps then I had to shrink that area of the wav by 48 x 40000 micro seconds or 1.92 seconds. After doing this in all 4 places the movie was perfectly in sync again and I was happy.

    2. When you try to reencode a movie that has some errors in it the audio will go out of sync where the errors are. Here to you can edit the .wav file to bring the movie back in sync as well.

    I just wanted to post this info up here in case anyone runs into the same problems to save them a little headache.


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