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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

  


• Is it possible to use FFmpeg to cut "random" sections from a folder of videos and concat them into 1 video ?

  14 novembre 2018, par EmmyStrand

  I realize this sounds like an easy question, and one that has been answered before. However, I cannot seem to find a script which can read a folder of videos with varying lengths, copy a random segment from each video, and concat them into a single video.

  An example :

  I have a folder with 150 videos labeled Fashion-Setlist-01.mp4, Fashion-Setlist-02.mp4, etc.
  Each are over 1 hour. I would like to pull a random 10 seconds section from each video and then randomly add them together resulting in a video. This may seem easy with only a few videos, but the plan is to read from potentially 100’s of videos. It should be possible to pull multiple sections from each video as well. I suppose we could run the script twice for more segments if the video needed to be longer.