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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).

  


• On Heroku I got FFMPEG::Error (Failed encoding.Errors : encoded file is invalid. Full output : )

  8 octobre 2020, par Ruslan Valeev

  The code is :

  


  tempfile = Tempfile.open('content')
tempfile.write(content)
movie = FFMPEG::Movie.new(tempfile.path)
screenshot_temp_file = Tempfile.open('screenshot')
movie.screenshot(screenshot_temp_file.path)


  


  everything works fine locally, but when I try this on Heroku I got error at last row :

  


  irb(main):013:0> movie.screenshot(screenshot_temp_file.path)&#xA;I, [2020-10-07T15:48:27.132114 #7]  INFO -- : Running transcoding...&#xA;["/app/vendor/ffmpeg/ffmpeg", "-y", "-i", "/tmp/content20201007-7-1g1955b", "-vframes", "1", "-f", "image2", "/tmp/screenshot20201007-7-1mmts7s"]&#xA;&#xA;E, [2020-10-07T15:48:27.190572 #7] ERROR -- : Failed encoding...&#xA;["/app/vendor/ffmpeg/ffmpeg", "-y", "-i", "/tmp/content20201007-7-1g1955b", "-vframes", "1", "-f", "image2", "/tmp/screenshot20201007-7-1mmts7s"]&#xA;&#xA;&#xA;Errors: encoded file is invalid. &#xA;&#xA;Traceback (most recent call last):&#xA;        7: from /app/bin/irb:30:in `<main>&#x27;&#xA;        6: from /app/bin/irb:30:in `load&#x27;&#xA;        5: from /app/vendor/ruby-2.6.6/lib/ruby/gems/2.6.0/gems/irb-1.0.0/exe/irb:11:in `<top>&#x27;&#xA;        4: from (irb):13&#xA;        3: from /app/vendor/bundle/ruby/2.6.0/gems/streamio-ffmpeg-3.0.2/lib/ffmpeg/movie.rb:204:in `screenshot&#x27;&#xA;        2: from /app/vendor/bundle/ruby/2.6.0/gems/streamio-ffmpeg-3.0.2/lib/ffmpeg/transcoder.rb:45:in `run&#x27;&#xA;        1: from /app/vendor/bundle/ruby/2.6.0/gems/streamio-ffmpeg-3.0.2/lib/ffmpeg/transcoder.rb:112:in `validate_output_file&#x27;&#xA;FFMPEG::Error (Failed encoding.Errors: encoded file is invalid. Full output: )&#xA;</top></main>

  


  I've try to pass some options, like :seek_time and validate: false but nothing changed. What am I doing wrong ? Thank you so much !

  


  EDIT :
After Full output: ) there is nothing.
I've install FFMPEG buildpack on Heroku, and can see it in ui :

  


  

  


• swscale/utils : override forced-zero formats back to full range

  10 octobre 2020, par Jan Ekström

  swscale/utils : override forced-zero formats back to full range
  Fixes vf_scale outputting RGB AVFrames with limited range flagged
  
  in case either input or output specifically sets the range.
  This is the reverse of the logic utilized for RGB and PAL8 content
  
  in sws_setColorspaceDetails.
  

  • [DH] libswscale/utils.c