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  1. Member
    Join Date: Feb 2005
    Location: Montreal
    Search Comp PM
    Hi all,

    I have the following problem with one AVI file in Xvid format, the audio duration of the original is 1:25:05 and after transcoding to any other format it changes to 1:24:54 whatever bitrate or samplerate i use in my conversion software, i have used like 5 differents software to transcode and all ends with the same results. Here are the details from the AVI file.
    * * * Media Inspector 0.7.443 file analysis report.
    * * * Media Inspector is 2011 by Diego Massanti - http://mediainfo.massanti.com
    * * * MediaInfoLib by Jerome Martinez - http://mediainfo.sourceforge.net
    Created on: 2012-02-23 13:56:10 HNE
    Report for file: Phantasm 1.avi

    General / Container Stream #1
    Total Video Streams for this File.................1
    Total Audio Streams for this File.................1
    Video Codecs Used.................................XviD
    Audio Codecs Used.................................MPEG-1/2 L3
    File Format.......................................AVI
    Play Time.........................................1h 25mn
    Total File Size...................................697 MiB
    Total Stream BitRate..............................1 144 Kbps
    Encoded with......................................VirtualD ubMod 1.5.10.2 Fr | www.trad-fr.com || (build 2540/release)
    Encoding Library..................................VirtualDu bMod build 2540/release
    Video Stream #1
    Codec (Human Name)................................MPEG-4 Visual
    Codec (FourCC)....................................XVID
    Codec Profile.....................................Simple @L3
    Frame Width.......................................576 pixels
    Frame Height......................................320 pixels
    Frame Rate........................................25.000 fps
    Total Frames......................................127639
    Display Aspect Ratio..............................16:9
    Scan Type.........................................Progr essive
    Color Space.......................................YUV
    Codec Settings (Packet BitStream).................No
    QF (like Gordian Knot)............................0.218
    Codec Settings (BVOP).............................No
    Codec Settings (QPel).............................No
    Codec Settings (GMC)..............................No warppoints
    Codec Settings (Matrix)...........................Default (H.263)
    Video Stream Length...............................1h 25mn 5s 560ms
    Video Stream BitRate..............................1 007 Kbps
    Bit Depth.........................................8 bits
    Video Stream Size.................................613 MiB (88%)
    Video Encoder.....................................XviD00 47
    Audio Stream #1
    Codec............................................. MPEG Audio
    Codec (FourCC)....................................55
    Audio Stream Length...............................1h 25mn 5s 544ms
    Audio Stream BitRate..............................128 Kbps
    Number of Audio Channels..........................2
    Sampling Rate.....................................48.0 KHz
    Audio Stream Size.................................77.9 MiB (11%)

    I have used MPEG2 Works 4 and a few other to transcode audio under OSX and even windows 7 or windows XP
    and got no success .

    is there something wrong with my method, i use virtualdubmod to demux my audio fro the AVI file, then try to process audio separately, which is the best i think, because i did it years ago.

    i have to say that my file framerate is 25 fps, the video that is. can it change something on the way i process it ?

    calculating the final lenght of the audio after conversion it corresponds to a framerate of 25.055 fps. what can cause this drift in the conversion process ?

    thanks in advance, and yes i did googled it for a long time before asking here.
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  2. I think MediaInfo is probably wrong about the length of the audio. Any audio I've ever muxed with XviD AVIs, if the audio is longer it gets truncated to the length of the video. After extracting the audio as MP3, does it still show that length when played in a player?

    Are you sure the audio isn't just shorter than the video to begin with? Have you tried muxing your MP2 or AC3 audio with the video to see if it loses synch? And if everything really is as you describe, that's what you get for downloading garbage from the internet (no B-Frames?).
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  3. Member
    Join Date: Feb 2005
    Location: Montreal
    Search Comp PM
    I guess you are right about media inspector, i opened the mp3 file in audacity and it report a lenght of 1:24:54, not 1:25:05. i will try to mux the files together to see if i have any audio sync drift.

    could you explain me what does B frames have to do with audio sync, i know that B frames are bi-directional predicted frames but the relation with audio for me is unknown.

    Thanks for the help
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  4. They have nothing to do with the audio, but since they're generally considered an important aid to compression, leaving them out entirely, either purposely or unintentionally, makes me wonder about the skill of the original encoder.
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