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• Cut a video in between key frames without re-encoding the full video using ffpeg ?

  1er septembre 2020, 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).

  


• ffmpeg and php to get an image out of a video and convert video to ogg

  6 mars 2016, par sonam Sharma

  I have a video hosting site and have successfully installed ffmpeg on my local server. Things work overall, but I cannot get the video duration and don’t know how to convert videos to the ogg format. I can convert videos to mp4 but am unsure if the same code can also convert to ogg.

  One more thing is that I can get a thumbnail out of the video at the start of the video but I want it after 50 seconds.

     $base = basename($uploadfile, $safe_file['ext']);
  
                  $new_file = $base.'mp4';
  
                  $new_image = $base.'jpg';
  
                  $new_image_path = $live_img.$new_image;
  
                  $new_flv = $live_dir.$new_file;
  
  
  
    equire 'vendor/autoload.php';
  
          //ececute ffmpeg generate mp4
  
          exec('ffmpeg -i '.$uploadfile.' -f mp4 -s 896x504 '.$new_flv.'');
  
          //execute ffmpeg and create thumb
  
          exec('ffmpeg  -i '.$uploadfile.' -f mjpeg -vframes 71 -s 768x432 -an '.$new_image_path.''); 

• How to cut a video to a certain length and add an intro video to it using ffmpeg-python ?

  16 juillet 2021, par kup

  How to cut a video to a certain length and add an intro video to it using ffmpeg-python ?

  


  What i am doing is :

  


          intro = ffmpeg.input(intro)
        mainvid = ffmpeg.input(mainvid)

        v1 = intro.video
        a1 = intro.audio
        v2 = mainvid.video
        a2 = mainvid.audio

        joined = ffmpeg.concat(v1, a1, v2, a2, v=1, a=1).node
        v3 = joined[0]
        a3 = joined[1]

        (
            ffmpeg
            .output(
                v3,
                a3,
                'out.mkv', 
                vcodec='libx265', )
            .run()
        )


  


  But i dont know how to cut mainvid to a certain length like 10 mins before joining, i know ss will help but dont know how to use it for only mainvid.