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  1. Member
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    Oct 2007
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    i am attempting to re-compress old avi files which has high quality audio streams in order to save some space. most of the avi's have ac3 5.1 audio streams. after i down mix them and re-merge them to avi i get sync problem.

    what i am doing is

    1. loading avi in VirtualDubMod and saving audio stream in wav or demuxing ( i have tried both)

    2. then disabling audio stream in VirtualDubMod and re-compressing avi with lower bitrate
    ( i am satisfied with re-compressed video stream)

    3. downmixing 5.1 ac3 (or wav) to 2.0. i have tried couple of ways to do this
    i tried Tranzcode_v0.40(beta), tried BeLight-0.22beta9 also AC3Machine.

    4. I merge avi with ac3(or wav) using VirtualDubMod

    i have also tried to leave sample rate, bit rate and sample size intact in downmixed audio streams in order to narrow down the problem. but no success yet

    so i was wondering what i am doing wrong here?

    any help or point in right direction is appreciated.

    thanks
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  2. Always Watching guns1inger's Avatar
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    Are the files out of sync by a constant amount the whole way through ?

    If so, determine the delay by opening the file in MPC and using the + and - keys on the number pad. Once you know the delay, open the avi in Virtualdubmod, click on Streams->Stream List, right-click and select Interleaving, and enter the delay in the bottom section of the dialogue. OK your way back to the main screen, then save a new version of the file in Direct Stream Copy mode and have a listen.

    If the sync drifts out gradually over time then you are screwing up the conversion somewhere, either by shifting frame rates or badly resampling.
    Read my blog here.
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  3. Member
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    i believe its constant... varies in different files. will have a go at it .. and but curious about better way to determine how much its off by.. i will reply with results

    thanks
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  4. Always Watching guns1inger's Avatar
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    There is no automated way to determine the delay once it's gone. You have to be able to line it up yourself based on dialogue or audio effects.
    Read my blog here.
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  5. Member
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    it worked.. thanks for you help. its too bad that there isnt automated way to do that.
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  6. Member
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    i was wondering wat you think about my approach to this matter... wat would be the best way to archive old videos and still preserver good video and audio quality? like xvid/divx or mp4 i think with mp4 you cant do much of editing... but how good are they compare to xvid or divx container?
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  7. Always Watching guns1inger's Avatar
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    If you have the processing grunt, then AVC in an MP4 container will give you higher quality in the same space as Divx/Xvid. You can't do real editing with either format, and re-encoding will quickly degrade them.

    It really depends on what they are, however the best option is to simply buy some large external HDD units and archive off to these without re-encoding. So far you have lost a generation in video quality, and thrown away perfectly good 6 channel audio and replaced it with lower quality stereo, all for the sake of a few MB. Better to keep the quality and just add more space.
    Read my blog here.
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  8. Member
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    so it isnt a good idea then... i think i just might back them up on dvd.

    thanks again
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