[Expert] 23.976 to 25 fps conversion "weird A/V sync prob"

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  • Ryan
    Junior Member
    Junior Member
    • Jan 2003
    • 8

    [Expert] 23.976 to 25 fps conversion "weird A/V sync prob"

    Hi all,

    First of all, I know my topic title indicates an often recurring question but I assure you it is a non standard issue so please read till the end.

    First of al some data. Below a picture of the output of Gspot with all data on the file I want to convert.



    Second, I use Virtualdub 1.5.10 stable in combination with the AC3ACM decoder (and I recompress with Lame ACM mp3 but thats of later concern)

    When I load the file in Vdub I leave everything default except for following settings:

    Video:
    1)Framerate -> Source rate adjustment -> Change to 25 frames per second
    2)Direct Stream Copy

    Audio:
    1)Use Advanced Filtering
    2)Filters -> [Input]->[stretch]->[output] (with a stretch (actually schrink) aspect ratio of 23.976 to 25 fps (0.9590409590))
    3)Full Processing mode

    After setting all this I choose save avi and wait till its finished.

    The output gives a file where the audio starts of early and slowly progresses to sync and out of sync again fluctuating onwards.

    In order to determine what causes this I tried several different settings for interleaving and preloading but none effective.

    To be able to trace the origin of te problem I extracted the Video and Audio and seperatly saved the streams on my HD. So I have an 23.976 fps avi file (no audio) and a 48000 khz wav file. When I open these in Media Player Classic the playback is allright (except for the fact that after a while the audio is out of sync due to 25 fps source requirement on a pal system).

    Now I seperatly convert the fps (vdub as descirbed above) and stretch the wav file (tried with vdub but also in cooledit/adobe audition) and still left them seperate on my HD. The playback is now out of sync (also after combining them with different interleave/preload settings). Because I know that cooledit is very precise in its stretch and the output format is allright I can only come to the conclusion the fps conversion of the video is not ok or something. Knowing only a parameter of the playbackspeed is changed I cannot say what could be wrong exept maybe that the source has dropped frames but thats a wild guess.

    I'll apreciate any suggestions.

    Greetings Ryan
  • reboot
    Digital Video Expert
    Digital Video Expert
    • Apr 2004
    • 695

    #2
    What is the end result of this conversion going to be?
    Storage on the hard drive, encoded to DVD, or for a standalone divx player?
    My DVDLab (and other) Guides

    Comment

    • Ryan
      Junior Member
      Junior Member
      • Jan 2003
      • 8

      #3
      The endresult will be storage on DvD (I've got over 60 GB of these files). The only thing I want to change is the fps since everything is in pal here.

      Comment

      • reboot
        Digital Video Expert
        Digital Video Expert
        • Apr 2004
        • 695

        #4
        You're going to have to extract audio.
        Change the framerate of video, and remux.
        My DVDLab (and other) Guides

        Comment

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