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  1. Hello,

    I have this MKV I extracted from a Blu-Ray with a good video track, and I also have an mp3 audio track in an other language that I extracted from the same movie but in a much lower resolution.
    I need to sync and mix this audio track with the video from the MKV
    BUT
    it seems that the audio from the lower resolution file is a bit faster.
    The movie length is full for both files but the lower resolution file is 5 minutes shorter.
    So I guess that before I can sync and mux that audio extract I will have to stretch it a bit without damaging the pitch, right?
    How do I do that?
    Isn't there a tool like the Subtitle Edit for subtitles that can edit an audio track where you just set 2 synced points at the beginning and the end and it just does the rest?

    Thanks
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  2. I'm a MEGA Super Moderator Baldrick's Avatar
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    Is it 4% shorter? And your blu-ray is 24fps and the low resolution is in 25fps?

    You can try goldwave and/or audacity. You can both stretch and adjust pitch in those. But you can't set any sync points.
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  3. Originally Posted by Baldrick View Post
    Is it 4% shorter? And your blu-ray is 24fps and the low resolution is in 25fps?

    You can try goldwave and/or audacity. You can both stretch and adjust pitch in those. But you can't set any sync points.
    In % I don't know. The BR file is of course 23.976 fps and the low-res avi file is 25 fps.
    But also if I read the info on both files in MediaInfo the BR is 1:35 whereas the AVI is 1:30.
    That's why I think I must stretch the audio I extracted from the AVI and then sync it because it is also not exactly starting at the same moment for some reason.
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  4. Member Cornucopia's Avatar
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    The difference between 1:35 @ 23.976 fps and 1:30 @ 25 fps, is 1663 frames, so stretching the timebase won't account for the difference. Sounds like you have editing to do, possibly a LOT.

    I'd consider using other sources...

    Scott
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  5. Assuming it's just a PAL vs NTSC speed difference, do it the other way around. Add the audio from the AVI to the MKV, delete the original audio, change the frame rate to 25fps, then save it as a new MKV. If the audio doesn't start at the same time you might also need to apply an appropriate audio delay, but by changing the frame rate of the video it means you won't need to re-encode the audio. You will of course need to keep two copies of the video with different audio tracks.

    If you want them in the same MKV, some audio converters have what's called PAL speedup and PAL slowdown. It's a little like a frame rate change for audio..... they know how much to speed it up or slow it down. Off the top of my head MeGUI's audio encoding section has options for speedup/slowdown. eac3to will do the same but it's command line. There's some GUI's for it you could try.
    http://forum.doom9.org/showthread.php?t=145574
    http://www.afterdawn.com/software/audio_video/convert_audio/eac3to_conversion_utility.cfm

    Once again you'd probably need to apply some sort of audio delay when muxing to put the audio in sync. Either a positive or negative dealy that moves the audio back.forward by a fixed amount. MKVMergeGUI can do that.

    There's absolutely no gurantee after all that the audio will match up. Sometimes the difference between two versions of a movie isn't just a speed difference. Sometimes they're edited slightly differently and the audio will never sync.
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  6. Wow!
    I am amazed. Never suspected it would be so complex. I am learning a lot from you guys.
    I will toy with this as you advised if only for the sake of learning.
    And about other sources, there are none unfortunately.
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