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  1. Hello, everytime I want to mux the audio from a BD rip with the video from another BD rip, and they have different fps/speed, I have to choose between speeding up the audio or the video.
    What is the best choice in term of quality? My goal is to perform the muxing operation for archiving and preserving quality as much as possible.

    In the past I used to speed up/down the video using mkv metadata, in order to not re-encode anything, and preserve quality. Recently a group of skilled encoders told me that speeding up the video can be wrong in cartoon, anime and CGI (all animation), because it can denature the animation itself (speed between one frame and another are very important to build the animation in cartoons/anime). Instead in live action it is less important, so we can prefer to speed up the video. What do you think about this concept?

    Anyway I suppose I have to avoid the audio speed up/down because I'll change the audio pitch and degrade the audio, expecially if it is from a lossy audio source (for example there are Bluray with AC3 lossy audio only).

    What should I do when I have to mux different sources?
    Last edited by precipizio; 14th Dec 2021 at 07:50.
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  2. Change the audio, leave the video as is.
    For simple audio change you can use clever FFmpeg-GUI.

    [Attachment 62361 - Click to enlarge]
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  3. ok I know how to do it with ffmpeg cli but I'd like to know why it is better (if it is).
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  4. Because a video recode is more noticeable than an audio recode
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  5. but I'd not re-encode the video, it's just a mkv container metadata.
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