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• ffmpeg - extract exact number of frames from video

  29 mars 2017, par Michael B

  I want to create a maximum of 30 images from a video (and tile them for a sprite sheet).

  I’ve tried using the ’select’ with ’mod’ but if the total number of frames does not fit neatly into the desired number of images (30) then I sometimes end up with more images, sometimes less.

  For example if my video is 72 frames long, my ’mod’ would be 72 / 30, which is 2.4.

  I’m running this from a python script so i’m doing something like the following for the filter :

  select='not(mod(n\," + str(mod) + "))'

  I think the mod has to be an integer (?) so I could either round down and use 2 which gives me 36 images or round up which gives me 24 images

  Whats the best way to get exactly 30 ? - obviously the interval wouldn’t be identical but thats fine.

  Maybe I could use a for loop to generate a list of the frames closest to the desired interval and then pass that in as the select filter ?

  e.g. to get the frames I would do something like this :

  nframes = 72 # number of frames in video
  
  outImages = 30 # number of images I want
  
  mod = float(nframes) / outImages # 2.4
  
  
  
  frames = []
  
  
  
  idx = 1
  
  
  
  while i < nframes:
  
      print str(idx) + ": " + str(math.floor(i+0.5)) 
  
      frames.append(int(math.floor(i+0.5)))
  
      idx += 1
  
      i += mod

  Then am I able to pass that (the frames list) into the ffmpeg command ? Or can I tell ffmpeg to do something similar ?

• Updated version number.

  1er septembre 2011, par Sebastian Tschan

  m jquery.fileupload-ui.js Updated version number.

• Updated version number.

  30 août 2012, par Sebastian Tschan

  m js/jquery.fileupload.js Updated version number.