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• How to stop perl buffering ffmpeg output

  4 février 2017, par Sebastian King

  I am trying to have a Perl program process the output of an ffmpeg encode, however my test program only seems to receive the output of ffmpeg in periodic chunks, thus I am assuming there is some sort of buffering going on. How can I make it process it in real-time ?

  My test program (the tr command is there because I thought maybe ffmpeg’s carriage returns were causing perl to see one big long line or something) :

  #!/usr/bin/perl
  
  
  
  $i = "test.mkv"; # big file, long encode time
  
  $o = "test.mp4";
  
  
  
  open(F, "-|", "ffmpeg -y -i '$i' '$o' 2>&1 | tr '\r' '\n'")
  
          or die "oh no";
  
  
  
  while(<f>) {
  
          print "A12345: $_"; # some random text so i know the output was processed in perl
  
  }
  
  </f>

  Everything works fine when I replace the ffmpeg command with this script :

  #!/bin/bash
  
  
  
  echo "hello";
  
  
  
  for i in `seq 1 10`; do
  
          sleep 1;
  
          echo "hello $i";
  
  done
  
  
  
  echo "bye";

  When using the above script I see the output each second as it happens. With ffmpeg it is some 5-10 seconds or so until it outputs and will output sometimes 100 lines each output.

  I have tried using the program unbuffer ahead of ffmpeg in the command call but it seems to have no effect. Is it perhaps the 2>&1 that might be buffering ?
  Any help is much appreciated.

  If you are unfamiliar with ffmpeg’s output, it outputs a bunch of file information and stuff to STDOUT and then during encoding it outputs lines like

  frame=  332 fps= 93 q=28.0 size=     528kB time=00:00:13.33 bitrate= 324.2kbits/s speed=3.75x

  which begin with carriage returns instead of new lines (hence tr) on STDERR (hence 2>&1).

• Tell pkg-config where to find packages on windows

  13 septembre 2016, par WirflBirfl

  I want to use the Haskell ffmpeg library under windows so I tried to install it via cabal.
  After downloading and extracting ffmpeg shared (64bit) version to C :\FFmpeg cabal complained that pkg-config was not installed.
  I downloaded it and moved it to the bin folder of MinGw. Now cabal complains that it can not find the pkg-config package libavutil.

  First part of the question :
  What is a pkg-config package ? Is it just the dll that comes with the shared version of ffmpeg ?

  Second part :
  I know pkg-config uses .pc files to describe where to look for packages and it uses the PKG_CONFIG_PATH variable to find .pc files. So how would a .pc file look when the libavutil dll is located in C :\FFmpeg\bin ?

  PS : The dll in FFmpeg\bin is named avutil-55.dll

  Thanks

• moving text in video with ffmpeg every 3 minute and 5 minute

  21 novembre 2018, par Amy Bomer

  I have a problem. I have found a tutorial on how to add text in videos using ffmpeg. but I want every 3 minute. I get the script only 10 second 1 time. I want 3 minute 1 time.

  my script :

  ffmpeg -i input.mp4 -filter:v drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSans.ttf:text='Hello World':fontcolor=white@1.0:fontsize=16:y=h-line_h-100:x=w/10*mod(t\,10):enable=gt(mod(t\,20)\,10)" -codec:v libx264 -codec:a copy -y output.mp4

  source of : here

  help me setting always 3 minute and speed text 10 second

  please ask for an explanation from each script above and please help so that every 3 minute the text appears

  thank you