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• ffmpeg - How to estimate CRF for h264 video target size

  10 septembre 2022, par the_RR

  According to the x264 encode documentation, in the CRF topic, it is informed that for every 6 additional points, the file size is reduced by approximately 50%.

  


  From this statement, it is assumed that the CRF has an exponential influence in reducing the final size of the video. But what is the exponential ratio ?

  


  I wouldn't want to use CRF18 with max-rate adjusted to reach a final size, as maxrate damage complex video scenes more strongly, as bitrate reduction via max_rate is not uniform, but it hits the scenes that require the highest bitrate first.

  


• How to properly abort av_seek_frame on FFmpeg ?

  5 mars 2021, par SuRGeoNix

  Normally, you wouldn't care aborting av_seek_frame as it would be really fast on a local file. However, in my case I use a custom AVIOContext for torrent streaming with custom read/seek functions and I'm not able to abort a single seek request !

  


  I've already tried interrupt callbacks (they will not be called at all), some timeouts (rw_timeout/timeout etc.) but by checking FFmpeg's code didn't find anything at all. My last chance was to try to return on read/seek functions an error (I've tried AVERROR_EXIT) which causes even more problems (memory leaks).

  


  The main issue is with Matroska formats that they need to resync (level-1) and they are trying to scan the whole file.

  


  Unfortunately, I'm using C# .NET with FFmpeg.Autogen bindings which means that I don't have low-level access to play around. My workaround is to re-open the whole format context in case on seek abort (to ensure that the player will continues to play at least)

  


  Hope you have a tip for me !

  


  (By the way for some http/hls web formats interrupt callbacks are supported)

  


• moviepy ffmpeg stderr to tkinter interface

  1er avril 2018, par Alexander Perlman

  Hi stackoverflow community,

  I’m a novice python hobbyist. I wrote a python / ffmpeg script using moviepy that batch concatenates videos. I then designed an interface using tkinter.

  Now I want to redirect the stderr output from FFMPEG to the tkinter interface so that users can review the progress directly in app instead of needing the Sublime text console.

  I’ve done a lot of research but I’m in way over my head. Any tips would be greatly appreciated.

  Here’s the moviepy component. The gui is pretty cut and dry

  #import video clips 
  
  mainvid = VideoFileClip(fullpath, audio=True)
  
  intro = VideoFileClip("intro.mp4", audio=True)
  
  black = VideoFileClip("black1s.mp4", audio=True)
  
  
  
  #concatenate video clips 
  
  final = concatenate_videoclips([black, intro, mainvid, black]) final.fps=24 
  
  
  
  #actually write file 
  
  final.write_videofile(output, audio=True, audio_fps=48000, ffmpeg_params=[ "-r","24000/1001", "-b:v", "50M", "-level:v", "4.1", "-c:a", "libvo_aacenc", "-b:a", "256K", "-colorspace", "bt709"])