Sync audio to video with different framarates

Discussion in 'Other video questions' started by dexter30, Sep 16, 2008.

  1. dexter30

    dexter30 Member

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    Hi guys,

    I looked averywhere and didn't find a clue on how to solve this problem.

    I recorder a movie from TV with my Panasonic DVD-Recorder at 29.970 FPS. No way to change that setting. Extracted audio with VDubMod (AUDIO 1).

    I want to sync AUDIO 1 to a DVD-movie audio (AUDIO 2), replacing the original audio track to be in sync with the movie. Don't want to mess with the video, want to adjust only AUDIO 1. This DVD-movie
    runs at 23.976 FPS. Impossible to find the same movie with 29.970 FPS.

    So tried to sync AUDIO 1 to AUDIO 2, looking for similar audio peaks and figures. Took a sample of 30min, cut start and end, shrink AUDIO 1 to match AUDIO 2 size, making two audios to begin and finish in sync.

    Problem is, AUDIO 1 and AUDIO 2 start to get async in the first minutes, and syncing them manually is a pain cause it's a task that has to be performed every 2 or 3 minutes. Sometimes AUDIO 1 is ahead, sometimes it is late. Don't really understand why.

    I tested the process with other 2 movies and result is the same.

    Please, any ideas will be welcome.

    Thanks!
     
    Last edited: Sep 16, 2008
  2. attar

    attar Senior member

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    Assuming the audio is the same (nothing cut out of the movie) except the length of the audio stream is different.

    You could load audio 2 wav into Audacity and check the exact running time in seconds (View => Set Selection Format => sec) - the running time is at the bottom of the window.

    Discard that file and load Audio 2.

    'Effects' => 'Tempo' and reset the running time to match Audio 1.
    Export the wav.

    Changing the tempo shouldn't change the pitch.
     
  3. dexter30

    dexter30 Member

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    I already did that, remember that I said I shrunk AUDIO 1 to match AUDIO 2 size? DidnĀ“t work, now it starts and ends in sync but looses it all in the middle.

    Thanks anyway!
     
  4. attar

    attar Senior member

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    Okey-dokey.
     
  5. davexnet

    davexnet Active member

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    hello -
    what is the running time of the two audio clips?
    Are they that different?

    I've seen things like this in the past. Usually the clip with the fewer
    fps has less total frames so that the run time is the same.

    I once tried to do what you're doing - in my case, clip "a"
    that I tried to add the audio from clip "b" - I couldn't get them to
    sync for the life of me. Took me a few hours before I realized
    that the clip "a" had a whole 4 minute scene, that was completely
    missing in the clip "b" version of the movie.
     
    Last edited: Sep 16, 2008
  6. dexter30

    dexter30 Member

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    AUDIO 1 is one minute or so longer than AUDIO 2. Even so they get async every minute, and the worst, sometimes AUDIO 1 is ahead, sometimes it is late..

    Maybe a solution would be to examine the videos instead of the audios to find if there are dropped frames?
     
  7. davexnet

    davexnet Active member

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    This is what I did - you may find out something similar to what I
    found - that the movies are slightly different edits (one of mine
    had an extra scene, as I said)

    I had to bring them up side by side and advance a minute or so
    in each one to find out where they differ.

    The 23.976 frame rate may turn out to be a red herring.
    When this NTSC f/r is played back, 3:2 pulldown is applied to the
    frames and 23.976 actually becomes 29.97.
     

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