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• FFMPEG : cut clips from a long video with "fast seek" while maintaining accuracy

  15 août 2020, par japseow

  I have this 3 hour long video which consists of <1-5 seconds of black frames> — < clip > — <1-5 seconds of black frames> — < clip > — ...

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  I could successfully get the clip without the black frames with the slow seek, but it takes over 4 minutes just for seeking.

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  ffmpeg -y -i "C:\Users\user\Videos\obs\part1.mp4" -ss 4370.48 -to 4384.95 -c:a copy -c:v hevc_nvenc -rc vbr_hq -cq 19 -b:v 10000k -maxrate:v 12500k "C:\Users\user\Videos\obs\____delete1.mp4"

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  I tried using the fast seek which takes only 4 sec, but it includes a 4 sec blackframe chunk at the end of the video. The output that should've been 14 sec long became 18 sec.

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  ffmpeg -y -ss 4370.48 -i "C:\Users\user\Videos\obs\part1.mp4" -to 14.47 -c:a copy -c:v hevc_nvenc -rc vbr_hq -cq 19 -b:v 10000k -maxrate:v 12500k "C:\Users\user\Videos\obs\____delete2.mp4"

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  My video has around 640 clips so it's impractical to wait that long just for seeking, and it'll only get worse when I'll be seeking at around the 2+ hour mark.

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• FFmpeg : How to convert horizontal video 16:9 to vertical video 9:16, with blurred background on top and bottom sides

  13 janvier 2016, par gomezo

  I know there is a post to do the contrary :
  FFmpeg : How to convert vertical video with black sides, to video 16:9, with blurred background sides

  but i can’t figure out how to do this with ffmpeg

  here is the input :

  

  and here is the expected result (the background video should be zoomed with the same aspect ratio, cropped to 9/16 and blurred) :

  

  Thanks for your help !

• Filter the video while keeping the bitrate (FFmpeg) [migrated]

  20 décembre 2013, par Timofey

  For experimental purposes, I need to filter my video (using -vf option) and change, say, brightness, but keep the same bitrate as in original video.

  Just for testing purposes, I change RGB values to make video completely black using line like this :

  ffmpeg -i input.mp4 -vf lutrgb='r=0.0*val:g=0.0*val:b=0.0*val' output.mp4

  So far, I tried to specify bitrate manually by adding -b, -minrate/maxrate and -q options to this line, but no matter what I do, FFmpeg keep reducing the br of the output video to just a few kilobytes.

  And my question is - if it's possible to keep bitrate on the same level even if if I change RGB values to be completely black (as an extreme case).