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• Cut a video in between key frames without re-encoding the full video using ffpmeg ? [closed]

  13 juillet 2024, par bguiz

  I would like to cut a video at the beginning at any particular timestamp, and it need to be precise, so the nearest key frame is not good enough.

  


  Also, these videos are rather long - an hour or longer - so I would like to avoid re-encoding this altogether if possible, or otherwise only re-encode a minimal fraction of the total duration. Thus, would like to maximise the use of -vcodec copy.

  


  How can I accomplish this using ffmpeg ?

  


  NOTE : See scenario, and my own rough idea for a possible solution below.

  


  ---

  


  Scenario :

  


  

  • Original video

    

    • Length of 1:00:00

    


    • Has a key frame every 10s

    


    


  


  • Desired cut :

    

    • From 0:01:35 through till the end

    


    


  


  • Attempt #1 :

    

    • Using -ss 0:01:35 -i blah.mp4 -vcodec copy, what results is a file where :

    


    • audio starts at 0:01:30

    


    • video also starts at 0:01:30

    


    • this starts both the audio and the video too early

    


    


  


  • using -i blah.mp4 -ss 0:01:35 -vcodec copy, what results is a file where :

    

    • audio starts at 0:01:35,

    


    • but the video is blank/ black for the first 5 seconds,

      

      • until 0:01:40, when the video starts

      


      


    


    • this starts the audio on time,
but the video starts too late

    


    


  


  


  ---

  


  Rough idea

  


  

  • (1) cut 0:01:30 to 0:01:40

    

    • re-encode this to have new key frames,
including one at the target time of 0:01:35

    


    • then cut this to get the 5 seconds from 0:01:35 through 0:01:40

    


    


  


  • (2) cut 0:01:40 through till the end

    

    • without re-encoding, using -vcodec copy

    


    


  


  • (3) ffmpeg concat the first short clip (the 5 second one)
with the second long clip

  


  


  I know/ can work out the commands for (2) and (3), but am unsure about what commands are needed for (1).

  


• How I can overlay video onto another video start from 2 second to 4 second ?

  23 janvier 2023, par KoliK

  I need overlay video onto another video start from 2 second to 4 second.

  


  I use ffmpeg for overlaying video onto another video for this command
ffmpeg -i tmp/test_screen_1672755242397.mp4 -vf "movie=tmp/test_camera_1672755249551.mp4, scale=250: -1 [inner]; [in][inner] overlay =10: 10 [out]" completed.mp4
But video test_camera_1672755249551 must be to star from 2 second and end to 4 second. What I need to add in command for result ?

  


• How to display a video with alpha channel on video FFMPEG

  5 novembre 2016, par AlfredMeier

  I want to put a video with alpha channel on a default video and stream this to YouTube. But I don’t know how to do that.

  Here is what I have done :
  ffmpeg -re -i video1.mp4 -codec copy -f flv rtmp://a.rtmp.youtube.com/live2/1234-1234-1234-1234

  Thanks for your help :)