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• Proportion for the values of maxrate, mnrate and bufsize for encoding videos for streaming purpose and past duration too large warning

  15 décembre 2015, par himanshu nautiyal

  can you please tell me about minrate, maxrate and bufsize. And is it necessary to give maxrate and minrate for encoding videos for streaming purpose. Actually I understood the meaning and functions of minrate, maxrate and bufsize through ffmpeg documents but I am not finding any solution of what would be difference in between the values of these three.

  for example : I am using this command
  ffmpeg -y -i testing.mp4 -c:a libfdk_aac -ac 2 -ab 128k -c:v libx264 -r 24 -g 24 -b:v 2m -maxrate 1m -bufsize 1m -vf scale=1920*1080 aa.mp4

  but I am not sure if this -b:v 2m -maxrate 1m bufsize 1m is in correct propotions or not. My output is fine but I don’t want any problem on working real time. Moreover, I am also getting the following warning

  Past duration 0.634361 too large
  Past duration 0.674370 too large
  Past duration 0.714363 too large 0kB time=00:00:01.32 bitrate= 0.3kbits/s

  Past duration 0.754372 too large
  Past duration 0.794365 too large
  Past duration 0.834373 too large
  Past duration 0.874367 too large
  Past duration 0.914360 too large
  Past duration 0.954369 too large

  thanks in advance

• FFMPEG filter_complex wih speedup and subtitles and scaling

  11 décembre 2015, par Sambir

  Hi I am trying to convert a file to a specific framerate and remove any jittering, jumping of the screen. I also try to boost the volume and add a subtitle overlay. I get an error with the curent line than it is not allowed to use complex_filter in combination with vf and af. as an extra I also would like to add text in the left corner (this i did not try yet) and would want the screen to be sized to full hd (changed scale to 1920:1080 but no succes).

  ffmpeg -i movie.mp4 -r 25 -filter_complex "[0:v]setpts=0.959*PTS[v];[0:a]atempo=1.0427[a]" -map "[v]" -map "[a]" -vf subtitles=sub.srt,scale=1920:1080 -af volume=2 -strict -2 -preset veryfast movie_new.mp4

  Got it !

  New :

  ffmpeg -i inside.mp4 -r 25 -filter_complex "[0:v]setpts=0.959*PTS[i];[i]scale=1920:1080[j];[j]subtitles=inside.srt[k];[0:a]atempo=1.0427[p];[p]volume=2[q]" -map "[k]" -map "[q]" -strict -2 -preset veryfast inside_new.mp4

  But now there is a new issue. Subs out of sync :P is there a easy fix for this or do i first need to encode without subs then resync then encode with subs ?

  found this link by the way Subtitle Resync Tool

  moviespeed is changed by 0.959. is there a calculation i can do to adjust the subtitles by x miliseconds ?

  EDIT : Got the subtitles fixed with subtitle workshop. Was just a small setting to change which directly shifted all the text :)

• FFMPEG Downgrade Only If 4k Video and Keep Aspect Ratio

  30 août 2020, par Devin Dixon

  Is there a way to downgrade video resolutions if and only if they are above a certain resolution ?

  


  For example, right now I am doing to :

  


  ffmpeg -i 4k_VIdeo.MP4 -vf scale=1920:1080 -c:v libx264 -crf 35 1080-video-smaller.mp4


  


  But if the video is 720:600 or a smaller resolution, I don't want to expand to 1920, also if the video is not the aspect ratio of 1920:1080, I want to keep the same aspect ratio so it doesn't look distorted.

  


  Is there a way of doing this ?