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• ffmpeg : fast video split by encoding only missing keyframes and copying the rest

  29 janvier 2023, par Eduardo Poço

  I am splitting a video in many files, removing the silent periods. The script is ready to detect the voiced parts, split and concat.

  


  At first, it thought copying the frames (-c copy) would be faster, but if a starting time of a part is not a keyframe, the video gets messed and some frames freeze until another keyframe appears. But reencoding each split file, although working, takes a long time.

  


  So, I was wondering if it is possible to reencode only the moments whose frames lost its keyframe, while copying everything so on. Is there a ffmpeg option for suck a task, or is there a way to differentiate those frames and treat them differently when splitting the file ?

  


  After reading some articles and documentation, that is how I understand what I am observing. Please, correct me if I misunderstood how ffmpeg works when splitting a file starting from a timestamp without a keyframe.

  


• Using -ss and -to to play a video using ffplay

  15 avril 2021, par Eswar T

  I want to display the video before trimming it

  


  to trim we can use 2 ways :

  


  method 1 :

  


  FFmpeg -i input.mp4 -ss 00:00:10.000 -to 00:00:15.000 output.mp4


  


  This Generates a video of length 5 seconds [Note here to is used we can also use -t]

  


  method 2

  


  FFmpeg -i input.mp4 -ss 00:00:10.000 -t 00:00:5.000 output.mp4


  


  This Generates a video of length 5 seconds[here we used -t so we specify duration]

  


  If I want to display a video I'm using

  


  FFplay -i input.mp4 -ss 00:00:10 -t 00:00:5


  


  but its starting video from 5 sec and to 15 sec [video length being 10 sec where it should be 10 sec to 15 sec [5 secs]]

  


  and if the file format is different again its starting at random points like for .mkv its stating at 8 sec to 15 sec
if im using -to im getting this error

  


  Failed to set value '00:00:15.123' for option 'to': Option not found


  


  im testing this from past 1 hr some one clear me how can i do ffplay for a trimming video
Thank you

  


• shell_exec echo'ing too fast or too late

  15 septembre 2016, par root

  So I read throug this article : https://trac.ffmpeg.org/wiki/PHP
  and found this :

  <?php
  
  echo "Starting ffmpeg...\n\n";
  
  echo shell_exec("ffmpeg -i input.avi output.avi >/dev/null 2>/dev/null &");
  
  echo "Done.\n";

  the code works almost perfectly fine, but the only thing that bothers me is, that because the shell_exec is being executed in the background (so there is no loading sign on the tab the whole time) all the echo’s are being executed immediatly. This means, that the "Done" echo is being written before ffmpeg finished its task.

  But when I remove the ’&’ the site does also what it is intended to do but now it waits until the shell_exec is finished until it echo’s out the "Starting ffmpeg..."

  So I kinda have the problem of figuring out how to get to such an order :

  1) echo something
  2) execute commad and wait until its finished.
  3) echo again

  I am a total beginner to php but have experience in programming overall. Please have mercy.

  Thank you for your time !