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Thread: Audio/video out of sync using Virtualdub

  1. #1
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    Default Audio/video out of sync using Virtualdub

    This was working fine until recently. Now every time I convert an mpg to an avi using Virtualdub, the audio and video progressively gets out of sync before the end of the file. I use the MPEG Layer-3 audio codec and the Divx video codec. I set the audio codec to 96 kbits/s, 44,100 Hz. Any help would be greatly appreciated. This is highly annoying as this is the second time I've run into this problem with Virtualdub. Thanks in advance.

  2. #2
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    Default

    interleaving!

  3. #3
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    Default

    I already have the interleaving enabled. Thanks for the reply though.

  4. #4
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    what's the interleaving set to? how many frames/ms?

    and which mp3 codec is it? vbr or cbr?

  5. #5
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    Default I have also had this problem

    Mostly with XviD and DivX, an MPEG-1 stream loses audio sync when converted. Sometimes I will cut out adverts from TV captures before compression, and obviously cut off anything recorded after the end of the credits. However, I always cut at keyframes.

    What seems to happen is that the audio gradually drifts. I encode using MP3/CBR at 128kbps usually.

    Are there some defaults in the interleaving or preload options which mess things up? Or should I be fixing Audio to fit with a slightly off framerate? It's all PAL TV so the framerate should be 25fps but maybe it skews.

    I'm interested in any guide or help on this.

  6. #6

    Default

    When my wife left me I broke everything and didn't have any money so I ended up using a P2 - 450

    I noticed no matter what kind of movie it was, if over, say, 50mb - I could not make the audio stay in time with the video..
    While I can think of no sane reason why a slower machine would encode improperly - that slower processor DID seem to put the sound and vid out of sync

    I am sure that's insane and illogical so don't pay attention

    I do know that if you overdrive a cpu it does start getting squirrley that's why distributed never did want overclockers working on their rc5 project because the overclocked cpus would lose packets or whatever they were I guess due to heat


    I'm babbling but the point (which became lost) is that if you are using a slower machine that's the problem with playback (it probably encodes fine)

    Anyone care for a drink

  7. #7

    Default

    Also
    Try the videos on another machine right away
    that's your first step (finding out if it's the system or the movies)
    also
    get a ballsy video card if you don't have one those are good to have

  8. #8
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    What about processing the audio and video seperatly and then multiplexing?

  9. #9
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    Default Multiplexing audio

    Yes, I can understand the suggestion of multiplexing. However, how can I load a 2 hour TV capture, delete adverts, and then trim either side of the credits... and still save a WAV correctly to multiplex back? If I go Save to WAV from Virtual Dub, then encode the video, the multiplex (by combining the two in Virtual Dub)... how is that essentially different from just processing everything in one easy step?

    I'm convinced that something is wrong... maybe my interleaving settings could change? Should I set interleaving every frame, every second, every n frames? Any good how tos out there?

  10. #10
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    Think I got a bit carried away with the previous concerning slower PCs - figured that encoding each part seperately, then multiplexing would ease the strain. But then you never said you had a slow PC

    Anyways, what happens if you don't use MP3 (i.e choose direct stream copy for the audio)?

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