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Avoid Sync Problems - Avi to VCD/SVCD

Discussion in 'User submitted guides' started by Dela, Jul 20, 2003.

  1. Dela

    Dela Administrator Staff Member

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    Ok I decided to write a bit on avoiding out of sync problems while encoding from AVI to VCD/SVCD

    Here are just some of the things that can cause the audio to be out of sync

    - The audio and video were seperated before encoding
    - You didnt use a reliable encoder
    - You dont have the appropriate codec installed or have codec conflict problems
    - The video stream has corrupted frames
    - You removed some frames and it went out fo sync

    That is just some of a lot of reasons. Now the first thing you should do when you get an AVI file is actually watch it and see for yourself if you have and sync problems or corrupted frames. If you have a sync problem where the audio is constantly behind by a second or something, then you can fix with virtualdub, but if you have a sync problem where the audio gradually falls further and further out of sync, that is impossible to fix!

    Corrupt frames can cause an encoder to stall for some time which will put the audio out of sync, or may stop the video stream altogether and let the audio continue. Below I have some tips for you

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    [bold]Check What Codecs Are Needed[/bold]
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    Check the AVI file first with GSpot or AVICodec to see do you have the appropriate codecs installed! This way you will make sure the file can be rendered properly.

    NOTE: just because the appropriate codecs are installed, the file may not playback because of some sort of codec conflict which will occur if you have install a crazy amount of codecs such as codec packs!!

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    [bold]Remove Any Corrupt Frames[/bold]
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    If you watched the AVI and say some corrupt frames along the way then you will need to remove them. The easiest way is by using AviFixed or DivFix

    NOTE: Before using either program, make a backup copy of your avi. If you use either and it removes frames but leaves messy playback, still attempt to encode as the encoder might still be able to render correctly!

    Another method for removing bad frames is VirtualDUB. Now if you use VirtualDUB you might have some problems with audio! The most common is removing corrupt frames and the audio goes out of sync in the AVI! I would suggest in that situation you try Nandub!

    In the case of AC3 audio, you will need VirtualDUBMOD to remove the corrupt frames!

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    [bold]Decompress The Audio In The File[/bold]
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    If you plan on using TMPGEnc to encode, you need to do this!

    You might have heard people saying seperate the audio and use that as your audio source but DO NOT do that! That is just asking for sync problems! Instead open your avi in virtualdub (doesnt work for ac3 sound, try virtualdubmod!)

    1. Click video - direct stream copy
    2. Click audio - full processing mode
    3. Click audio - Compression, select no compression pcm and click ok
    4. click file - save as avi

    Now use the AVI aved with TMPGEnc!

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    [bold]Allow Encoding To Work On Its Own[/bold]
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    Dont be using your computer for anything while encoding. Especially with TMPGEnc, that will cause sync problems for definite!

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    [bold]For TMPGEnc, Use External Audio Encoders[/bold]
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    If you click option - environmental setting in TMPGEnc and click Audio Engine, you will see the oportunity to select an external encoder for mp2! I recommend you download tooLame and use it as your external encoder and for Sampling Frequency Converter, use SSRC! I found less sync problems while these programs were used!

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    [bold]DVD2SVCD Highly Recomended[/bold]
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    I highly recomend using DVD2SVCD because the audio is encoded first then the video. bbMPEG multiplexes and its rare to get a sync problem.

    With DVD2SVCD you can use either TMPGEnc, Canopus ProCoder or CCE SP as your encoder! CCE SP is the best for MPEG-2 IMHO and TMPGEnc is the best for MPEG-1 IMHO!

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    [bold]Final[/bold]
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    This thread is just to give tips on how to avoid sync problems. I know it is not that compreshensive but if you have any questions use the VCD/SVCD forum!

    I will add more tips as I find them!
     

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