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  1. Member
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    I have two versions of the same film - (3 GB 23.976 fps file with croatian audio and 700 MB 25 fps file with English audio) - only the film lengths are different by a few minutes. I want to put English audio with the 23.976 fps video file.

    I understand that audio does not have frame rates, only lengths, so I can use Audacity to stretch/shrink audio without altering pitch before joining.

    Can I do this with any of the mkv tools? If so, how?

    Thanks.
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  2. Extract the audio you want with MkvExtractGUI, change the rate in Audacity, then mux the new audio with the video track you want with MMG.

    Or you could just mux the audio and video tracks you want, changing the frame rate of the video.

    But, you'll often find that PAL and NTSC releases of a movie are different cuts. So neither of the above will work.
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    Thanks, jagabo.
    Yes, different cuts are real issues.
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  4. Yeah, check the frame count for them both to see if they're the same or not. Allow for any opening logos being different, if they are different
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    When I tried using Audacity to stretch PAL audio several years ago, its stretch only went to two decimal places of precision, so the sync still drifted off over the length of a movie. Virtualdub's stretch, on the other hand, goes to five decimals (1.04271), and sync stopped being an issue.
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  6. I tested Audacity recently and with the Change Speed filter, although the slider only gives you 3 digits to the right of the decimal point, you can type in a value with more digits and it uses the more precise value. If you go back to the dialog later the value you typed in is truncated or rounded to three digits. So if you need to change a second file you have to type in the full precision value again. I don't know if the Change Tempo filter does the same similarly.
    Last edited by jagabo; 27th Sep 2013 at 19:33.
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    Originally Posted by Calidore View Post
    Virtualdub's stretch goes to five decimals (1.04271), and sync stopped being an issue.
    Thanks, Calidore. Forgotten how VirtuadDub stretches, but wouldn't the pitch be an issue? And, manono, long time no see, and that's only because I didn't visit the fora. As far as my memory goes, you are based in Hawaii. How's AGK doing nowadays?
    Last edited by ukb007; 28th Sep 2013 at 01:19. Reason: Add new thoughts.
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    Originally Posted by ukb007 View Post
    Originally Posted by Calidore View Post
    Virtualdub's stretch goes to five decimals (1.04271), and sync stopped being an issue.
    Thanks, Calidore. Forgotten how VirtuadDub stretches, but wouldn't the pitch be an issue?
    It would. Your PAL source may have 4%-speedup-sound, in which case this will correct it, or it doesn't. That's up to your ear, really. Virtualdub does also have a "time stretch" filter, but the one time it tried that, it really messed up the sound.

    In the end, Audacity is specifically for modifying sound and Virtualdub isn't. Since Jagabo says that you can have the correct precision, I'd say go with that unless Virtualdub used this way is more convenient for your needs.
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  9. Both Audacity and VirtualDub have the ability to change the length of the audio with or without pitch shift. And the ability to pitch shift without changing the length. I can't attest to the quality of each.
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