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  1. Hey, I don't know if this is the ideal topic for this subject but here it goes:
    So, I have an MP4 file, but after the 10min mark the audio gets delayed. Is there any program to delay audio ONLY from that point? Because I know there is some that delay all the video audio.

    If not, is there any program that "extracts" the video and the audio, so that I can edit the audio on an editing program?

    Thank you in advance
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  2. Member hech54's Avatar
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    Just try dragging the MP4 video file into something like Audacity or Goldwave?
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  3. Try MP4Box GUI for extracting the audio and remuxing MP4s.

    I tend to try splitting the file, creating a new copy of the second half with a corrected audio delay, then I append that to the first section again. That often works well, as long as you can split where the audio sync changes. You should be able to do all that with My MP4Box but I generally use MKVMergeGUI as it's easier to use. It'll open and split MP4s (and other file types), but the output container will be MKV.
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  4. Originally Posted by hello_hello View Post
    Try MP4Box GUI for extracting the audio and remuxing MP4s.

    I tend to try splitting the file, creating a new copy of the second half with a corrected audio delay, then I append that to the first section again. That often works well, as long as you can split where the audio sync changes. You should be able to do all that with My MP4Box but I generally use MKVMergeGUI as it's easier to use. It'll open and split MP4s (and other file types), but the output container will be MKV.
    Yeah that seems like a good idea. I knew about MKVtoolnix, I was wondering about the same but with mp4, that's exactly what I wanted, thanks!!

    Now, the audio format is .aac
    What program can edit this kind of format?
    Or do I have to convert it in order to edit it?
    Last edited by hugopiugo; 23rd Oct 2015 at 15:05.
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  5. MP3DirectCut can be used to edit AAC (cut sections or paste them etc). You need libfaad2.dll in the Mp3DirectCut folder to decode it, but I think MP3DirectCut provides a link when you try to listen to AAC without it.
    It won't open MP4/M4A files though, only the raw AAC, so you need to extract it, and it doesn't play multi-channel AAC correctly, although I think you can still edit it.

    I usually work out the required delay while playing the video in MPC-HC and tapping the +/- keys, and most of the time if a delay (as an example) of -120ms is required, removing 120ms from an appropriate place in the audio with MP3DirectCut works fine. Every so often though (probably only for VBR audio) cutting/pasting an appropriate amount with MP3DirectCut doesn't fix the sync as it should. I think that's MP3DirectCut not displaying the audio time-frame accurately (although it has a setting labelled "use TOR correction on VBR" which may help) but that's one reason I tend to try fixing the sync by splitting the file, adjusting, then joining them again with MKVMergeGUI. Whatever works though....
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  6. locotus
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    Ocenaudio opens mp4 with aac audio and let you edit the audio.
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