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• How to change part of a MKV video with another MKV video without re-encode and without changing audio file of the primary MKV file [closed]

  10 octobre 2020, par MonsterMMORPG

  I have a lecture that I have recorded with using OBS studio and my microphone

  


  But I want to replace certain part of that video with another video without re-encoding or touching the audio

  


  The another video is also recorded with OBS studio with the same settings

  


  If encoding is necessary I accept that as well

  


  So what would be the appropriate ffmpeg command ?

  


  Here example file definitions and durations to give more clear example

  


  


  • a.mkv : 77 minutes long

    


  


  • b.mkv : same format and 2 minutes long

    


  


  • c.mkv : I want to replace 00.23.00 - 00.25.00 part of a.mkv with b.mkv without changing the audio file of a.mkv

    


  


  


  Is this possible without encoding or with re-encoding ?

  


  So can you provide an example code with some definitions

  


  How do we define starting position, the durations ? I found some examples on the Internet but they were not definitive enough

  


  Answer to this question : https://superuser.com/questions/1591877/how-to-change-part-of-a-mkv-video-with-another-mkv-video-without-re-encode-and-w

  


• How to download a part of mp3 from server ?

  20 août 2020, par Sharukh Mohammed

  Use Case

  


  My use case is roughly equal to, adding a 15-second mp3 file to a 1 min video. All transcoding merging part will be done by FFmpeg-android so that's not the concern right now.

  


  The flow is as follows

  


  

  • User can select any 15 seconds (ExoPlayer-streaming) of an mp3 (considering 192Kbps/44.1KHz of 3mins = up to 7MB)

  


  • Then download ONLY the 15 second part and add it to the video's audio stream. (using FFmpeg)

  


  • Use the obtained output

  


  


  Tried solutions

  


  


  • Extracting fragment of audio from a url

    


    RANGE_REQUEST - I have replicated the exact same algorithm/formula in Kotlin using the exact sample file provided. But the output is not accurate (± 1.5 secs * c) where c is proportional to startTime

    


  


  • How to crop a mp3 from x to x+n using ffmpeg ?

    


    FFMPEG_SS - This works flawlessly with remote URLs as input, but there are two downsides,

    


    

    1. as startTime increases, the size of downloaded bytes are closer to the actual size of the mp3.

    


    2. ffmpeg-android does not support network requests module (at least the way we complied)

    


    


  


  


  So above two solutions have not been fruitful and currently, I am downloading the whole file and trimming it locally, which is definitely a bad UX.
I wonder how Instagram's music addition to story feature works because that's close to what I wanted to implement.

  


• How to stream only a part of a video without downloading the whole thing ?

  11 mai 2024, par Abbas

  I am building a YouTube video trimmer, and currently, it takes the YouTube video ID, downloads the whole video from the server (Even it is like 10 hours long), and then it trims it according to user's inputted timeframe using ffmpeg.

  


  Now the problem with this is that it takes so much time to download the whole video even if we want a small piece of it hence it is highly impractical.

  


  I was thinking to implement something like an HTML5 video player does when you seek the video forward. It just jumps to the part where you seek-ed to without downloading the part you skipped over. How can I only download a part of a video file from a server in form of a buffer and then generate an already trimmed video file from that ? I don't know if that is even possible on the server-side, but video players do it on the client-side.