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• Tell libavcodec/ffmpeg to drop frame

  7 mars 2013, par chouquette

  I'm building an app in which I create a video.
  Problem is, sometime (well... most of the time) the frame acquisition process isn't quick enough.

  What I'm currently doing is to skip the current frame acquisition if I'm late, however FFMPEG/libavcodec considers every frame I pass to it as the next frame in line, so If I drop 1 out of 2 frames, a 20seconds video will only last 10. More problems come in as soon as I add sound, since sound processing is way faster...

  What I'd like would be to tell FFMPEG : "last frame should last twice longer that originally intended", or anything that could allow me to process in real time.

  I tried to stack the frames at a point, but this ends up killing all my memory (I also tried to 'stack' my frames in the hard drive, which was way to slow, as I expected)

  I guess I'll have to work with the pts manually, but all my attempts have failed, and reading some other apps code which use ffmpeg, such as VLC, wasn't of a great help... so any advice would be much appreciated !

  Thanks a lot in advance !

• ffmpeg to make black video with multiple audio and subtitles [closed]

  9 septembre 2024, par Tony M

  I want to use ffmpeg to make a video with only audio and subtitles in different languages. The video part can be a simple black background. I want to be able to switch between languages in video players like QuickTime.

  


  I've tried to get help from posts like this, but I couldn't figure out how to get it to work.

  


  To demonstrate that I've worked a long time on this, I'm showing what I've come up with below — but only steps (1) & (2) work. I can't get the subtitles step (3) to work.

  


  I've used ffmpeg for a long time, but never really understood it... I've only recently started to build my own commands, so the following probably looks awful to an expert :

  


  


  1. make a silent video using

     


     ffmpeg -loop 1 -i black.jpg -i silent.mp3 -acodec copy -shortest -vf scale=1000:136 silent.mov

     


  


  


  where m.jpg is a 500x68 black image and m.mp3 has 5 min of silence

  


  


  2. add 3 language (italian, french, german) using

     


     ffmpeg -i silent.mov -i ita.mp3 -i fre.mp3 -i ger.mp3 -map 0:v -map 1:a -map 2:a -map 3:a -metadata:s:a:0 language=ita -metadata:s:a:1 language=fre -metadata:s:a:2 language=ger ita-fre-ger.mov

     


  


  3. add subtitles using (doesn't work)

     


  


  


  ffmpeg -i ita-fre-ger.mov -i ita.srt -i fre.srt -i ger.srt -map 0 -map 1 -map 2 -map 3 -c copy -c:s mov_text -metadata:s:s:0 language=ita -metadata:s:s:1 language=fre -metadata:s:s:2 language=ger final.mov

  


• Concatenate multiple video php ffmpeg

  3 mai 2017, par Angus Simons

  I have multiple files that are already been encoded (they have the same format and size) I would like to concatenate on a single video (that already exist and has to be overwritten).

  Following the official FAQ Documentation I should use demuxer

  FFmpeg has a concat demuxer which you can use when you want to avoid a
  re-encode and your format doesn’t support file level concatenation.

  The problem is that I should use a .txt file with a list of files using this command line

  ffmpeg -f concat -safe 0 -i mylist.txt -c copy output

  where mylist.txt should be :

  file '/path/to/file1'
  
  file '/path/to/file2'
  
  file '/path/to/file3'

  How can I do with PHP ?

  ---

  Also tried with concat protocol

  I tried using also the concat protocol that re-encode videos with these lines of code :

  $cli = FFMPEG.' -y -i \'concat:';
  
  
  
  foreach ($data as $key => $media) {
  
    $tmpFilename = $media['id'];
  
    $tmpPath = $storePath.'/tmp/'.$tmpFilename.'.mp4';
  
  
  
    if ($key != ($dataLenght - 1)) {
  
      $cli .= $tmpPath.'|';
  
    } else {
  
      $cli .= $tmpPath.'\'';
  
    }
  
  }
  
  
  
  $cli .= ' -c copy '.$export;
  
  exec($cli);

  that generate this command line :

  /usr/local/bin/ffmpeg -i 'concat:/USER/storage/app/public/video/sessions/590916f0d122b/tmp/1493768472144.mp4|/USER/storage/app/public/video/sessions/590916f0d122b/tmp/1493767926114.mp4|/USER/storage/app/public/video/sessions/590916f0d122b/tmp/1493771107551.mp4|/USER/storage/app/public/video/sessions/590916f0d122b/tmp/1493771114598.mp4' -c:v libx264  /USER/storage/app/public/video/sessions/590916f0d122b/tmp_video_session.mp4

  but I got this error :

  [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fc8aa800000] Found duplicated MOOV Atom. Skipped it