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• How to mix audio description track into stereo mix in FFMPEG or SOX

  4 mai 2022, par Overlook Motel

  I have a video file with a stereo mix. I have also been provided with an additional audio description track (a narration which describes what's happening on screen for visually-impaired audiences) as a mono WAV.

  


  I am trying to mix the two together, however the tricky part is adjusting the levels. The levels of the main mix should be dipped before and raised back again after each line of speech in the AD track.

  


  The company who produced the AD track have offered to do this for a fee, however I noticed that their fee is static regardless of the length of the film, so I assume it must be an automated process (if it involved a sound mixer in a studio, it'd be charged at a per minute rate).

  


  I'm wondering if it's possible to do this myself in FFMPEG.

  


  The AD track is cleanly recorded at a consistent level and is entirely silent in between the lines of narration. So imagine it would be in principle possible to determine where the main mix needs to go up and down.

  


  Would probably need to :

  


  

  1. Analyse the levels of the AD track and convert to a list of "fade down here", "fade up here" instructions.

  


  2. Apply that list of instructions to the main mix to create an intermediate.

  


  3. Mix together the intermediate with the AD track.

  


  


  The final step could be achieved with the amix filter, but I have little idea how to approach the first 2 steps.

  


  Does anyone know if this is achievable with FFMPEG ? I'd also be open to using other programs such as SOX.

  


• How to detect added scenes in Director's Cut Edition of movie ?

  17 juillet 2019, par B Lolo

  I’ve got huge collection of .mkv files. In every movie folder there are two files : one original movie and one extended edition of that movie.

  Two files can be different for example one is 480p and the second 1080p.

  One can be 1 hour long, second one 40 minutes.

  In those extended edition files scenes are added randomly, so it could be 2 minutes in beginning, 5 minutes after first 10 minutes of the film and so on.

  Is there a way to use Python and ffmpeg to detect scenes from extended edition files that are absent in original movie file ?

  I can also work with only audio if that is easier to do.

  For now I got idea to use ffmpeg and scene detection, I can manually search for differences between files, but I would like some hints where to look changes.

  This is python code with ffmpy library :

  from ffmpy import FFmpeg
  
  
  
  plik = "C:/special.mkv"
  
  png = re.sub("\.mkv","_changes.png",plik)
  
  
  
  ff = FFmpeg(executable='C:/ffmpeg.exe', global_options ='-v error', inputs={plik : ''}, outputs={png : "-vf select='gt(scene\,0.4)',scale=320:-1,tile=10x80 -frames:v 1 -y"})
  
  result = ff.run(stdout=PIPE, stderr=PIPE)

• stream mp4 file with ffmpeg from a specific time of video

  15 décembre 2019, par Reza Torkaman Ahmadi

  I Want to stream a video file (.mp4) from a differnt starting time.

  For example I want to stream test.mkv file from minute like 00:02:30 of test.mkv video.
  So when I stream it to rtmp server, the video is started from 00:02:30 of movie not start.
  Note : I don’t want to wait for that long, I want to start from that moment right after i pressed enter on ffmpeg command, So answers like using cronjob are not useful.

  Here is the ffmpeg command i’m using :

  ffmpeg -i test.mkv -pix_fmt yuv420p -vsync 1 -threads 0 -vcodec libx264 -r 30 -g 60 -sc_threshold 0 -b:v 512k -bufsize 640k -maxrate 640k -preset veryfast -profile:v baseline -tune film -acodec aac -b:a 128k -ac 2 -ar 48000 -af "aresample=async=1:min_hard_comp=0.100000:first_pts=0" -bsf:v h264_mp4toannexb -f flv rtmp://test.server.com

  Note :

  If you guys have any suggestions on improving ffmpeg commmand, also I appreciate it.