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• Remove parts of a video automagically without reencode ?

  21 août 2022, par Sam

  I'm looking for a way to remove automatically the opening and ending parts of a video (credits) without reencode.

  


  If you need an example, take Game of Thrones : I'd need a way to automatically remove the GoT opening (with the theme music) and the ending part (with the credits and the HBO logo part).

  


  FFmpeg can do that, but the cut has to be manual and happens only at keyframes... which isn't precise enough for me.

  


  I thought that maybe there is a tool that allows to scan a video, and remove a part between two input frames (the start of opening frame, the end of opening frame)... etc, same thing for Ending.

  


  Thanks for the help !

  


• ffmpeg encode video with different rates [on hold]

  12 août 2013, par alexis

  I have two videos. I make this videos with the following codes :

    ffmpeg -r 5 -f image2 -i "b%d.png" -c:v mpeg4 -q:v 5 -an a.avi 
  
    ffmpeg -r 15 -f image2 -i "b%d.png" -c:v mpeg4 -q:v 5 -an b.avi 

  As you can see, the only difference is the rate. Now I want to concatenate them. Following the other post I use this :

    ffmpeg -i "concat:a.avi|b.avi" -c copy movie2.avi

  However the resulting movie shows the "b.avi" part much more slower. Actually no difference of speed is appreciated between "a" and "b" parts. How can I keep the differences of speed in the resulting movie ?

  Maybe I have some conceptual misunderstanding about rate... but the thing is that I want the "b.avi" part to be faster than the "a.avi" part.

• audio discontinuity in ffmpeg joined youtube video

  1er novembre 2016, par MrPeach

  I downloaded 4 parts of a video of youtube, and I wanted to join them.

  My first (conservative) attempt :

  echo file 'Part 1.mp4' > m
  
  echo file 'Part 2.mp4' >> m
  
  echo file 'Part 3.mp4' >> m
  
  echo file 'Part 4.mp4' >> m
  
  ffmpeg -f concat -i m -c copy 1a.mp4

  Result : A/V sync good, at transition video garbled, audio discontinuity

  Second (extreme) attempt :

  echo file '1.avi' > m
  
  echo file '2.avi' >> m
  
  echo file '3.avi' >> m
  
  echo file '4.avi' >> m
  
  
  
  ffmpeg -y -i "Part 1.mp4" -f avi -acodec pcm_s16le -ac 2 -ar 44100 -vcodec rawvideo -pix_fmt yuv420p 1.avi
  
  ffmpeg -y -i "Part 2.mp4" -f avi -acodec pcm_s16le -ac 2 -ar 44100 -vcodec rawvideo -pix_fmt yuv420p 2.avi
  
  ffmpeg -y -i "Part 3.mp4" -f avi -acodec pcm_s16le -ac 2 -ar 44100 -vcodec rawvideo -pix_fmt yuv420p 3.avi
  
  ffmpeg -y -i "Part 4.mp4" -f avi -acodec pcm_s16le -ac 2 -ar 44100 -vcodec rawvideo -pix_fmt yuv420p 4.avi
  
  
  
  ffmpeg -f concat -i m -c:a libvo_aacenc -c:v h264 1b.mp4

  Result : A/V sync issues in first section, at transition slight jump in video, audio discontinuity

  I have no idea how to fix this. Thoughts ?

  Update :

  Both the audio and video exhibit issues - skipping and duplication of a short section at some joins.

  My ultimate solution was to check the a&v section joins for duplication and trim that off if it exists, and for the audio cut out any silence sections as best as the waveform allowed. Lastly, modify the audio tempo to match the length of the video.

  It’s a terrible hack, but it’s what I’m stuck with. If anyone ever comes up with a better approach, I’d love to hear of it.