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  1. Member b1tbull's Avatar
    Join Date: Jun 2010
    Location: Belgium
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    Greetings,

    Starting point : commercial DVD containing 23 video clips.
    Facts : each video clip is encoded as a single VOB file ( streams are mpeg 2 and PCM )
    The (currently free ) makemkv tool allows to convert the whole set into 23 mkv files.
    Those 23 files are then merged with mkvmergeGUI into one mkv container ( see mediainfo below ).
    So far so good. Both audio and video are 1h 35 min. All in sync from start to end when played on PC ( Media Player Classic ).
    Now time to demux that 1h 35 min mkv into separate video and audio files using mkvextract.
    Mediainfo duration for audio ( .wav file ) is still 1h 35 min.
    Mediainfo duration for video ( . mpg file ) is only 4 min 17 sec, video duration in MPC and WMP is 1h 25 min 14 sec.
    Muxing audio and video back into one mkv container with mkvmergegui results into a file where
    the audio and video are in sync initially, but video is lagging more and more on audio.
    Mediainfo on that remuxed mkv file shows again 1h 35 min both for audio and video.

    Any help in figuring out why audio is getting out of sync after demux/remux ( which should restore the
    original content ) is greatly appreciated.
    Tried already most obvious solutions like stretch values in mkvmergegui.

    ------------------------------ mediainfo MKV container merged from 23 individual mkv files ---------------------------------
    Complete name : I:\Videos\Movies\MakeMKV\large\ar.mkv
    Format : Matroska
    File size : 5.71 GiB
    Duration : 1h 35mn
    Overall bit rate : 8 538 Kbps
    Encoded date : UTC 2010-08-22 15:44:32
    Writing application : mkvmerge v4.2.0 ('No Talking') built on Jul 28 2010 18:38:23
    Writing library : libebml v1.0.0 + libmatroska v1.0.0

    Video
    ID : 1
    Format : MPEG Video
    Format version : Version 2
    Format profile : Main@Main
    Format settings, BVOP : No
    Format settings, Matrix : Default
    Codec ID : V_MPEG2
    Codec ID/Info : MPEG 1 or 2 Video
    Duration : 1h 35mn
    Bit rate mode : Variable
    Nominal bit rate : 7 000 Kbps
    Width : 720 pixels
    Height : 576 pixels
    Display aspect ratio : 4:3
    Frame rate : 25.000 fps
    Standard : PAL
    Color space : YUV
    Chroma subsampling : 4:2:0
    Bit depth : 8 bits
    Scan type : Interlaced
    Scan order : Top Field First
    Bits/(Pixel*Frame) : 0.675

    Audio
    ID : 2
    Format : PCM
    Codec ID : A_PCM/INT/LIT
    Duration : 1h 35mn
    Bit rate mode : Constant
    Channel(s) : 2 channels
    Sampling rate : 48.0 KHz
    Bit depth : 24 bits
    Title : 2/0

    ------------ mediainfo remuxed mkv file , audio increasingly out of sync ------------------------------------

    Complete name : I:\Videos\Movies\MakeMKV\large\armuxed.mkv
    Format : Matroska
    File size : 5.71 GiB
    Duration : 1h 35mn
    Overall bit rate : 8 535 Kbps
    Encoded date : UTC 2010-08-23 14:22:08
    Writing application : mkvmerge v4.2.0 ('No Talking') built on Jul 28 2010 18:38:23
    Writing library : libebml v1.0.0 + libmatroska v1.0.0

    Video
    ID : 1
    Format : MPEG Video
    Format version : Version 2
    Format profile : Main@Main
    Format settings, BVOP : No
    Format settings, Matrix : Default
    Codec ID : V_MPEG2
    Codec ID/Info : MPEG 1 or 2 Video
    Duration : 1h 35mn
    Bit rate mode : Variable
    Nominal bit rate : 7 000 Kbps
    Width : 720 pixels
    Height : 576 pixels
    Display aspect ratio : 4:3
    Frame rate : 25.000 fps
    Standard : PAL
    Color space : YUV
    Chroma subsampling : 4:2:0
    Bit depth : 8 bits
    Scan type : Interlaced
    Scan order : Top Field First
    Bits/(Pixel*Frame) : 0.675

    Audio
    ID : 2
    Format : PCM
    Codec ID : A_PCM/INT/LIT
    Duration : 1h 35mn
    Bit rate mode : Constant
    Channel(s) : 2 channels
    Sampling rate : 48.0 KHz
    Bit depth : 24 bits
    Periculum in mora
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  2. Mod Neophyte Super Moderator redwudz's Avatar
    Join Date: Sep 2002
    Location: AZ, USA
    Search Comp PM
    It sounds like you want one single video from the 23 clips? If so I would probably use VOB2MPG to extract them to one large MPEG, then convert to MKV. I've used XviD4PSP for that.
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  3. Member b1tbull's Avatar
    Join Date: Jun 2010
    Location: Belgium
    Search Comp PM
    Thanks for the feedback.

    I had already 23 MKV files extracted from the DVD using makemkv.
    Your suggestion for XviD4PSP did the job, allowing to convert those 23 mpeg2 mkv files
    to mpeg4 mkv files while maintaining the PCM audio.
    Mkvmerge was then able to get everything into one mkv container with no audio sync issues anymore.
    XviD4PSP is here to stay in my toolbox now.

    Originally Posted by redwudz View Post
    It sounds like you want one single video from the 23 clips? If so I would probably use VOB2MPG to extract them to one large MPEG, then convert to MKV. I've used XviD4PSP for that.
    Periculum in mora
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