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• How to reduce fps to reduce filesize using ffmpeg ?

  10 septembre 2024, par Asas

  I recorded the video in waaaay to high of fps and its like over 100 gb now, i dont want any quality degradation just to lower the fps to a reasonable 60 but when i googled i got the result which converted my video but the size is the same for some reason
I tried

  


  ffmpeg -y -i input_video.mp4 -c copy -f h264 output_raw_bitstream.h264
ffmpeg -y -i input_video.mp4 -vn -acodec copy output_audio.aac
ffmpeg -y -r 24 -i output_raw_bitstream.h264 -i output_audio.aac -c copy output.mp4


  


  but replaced numbers and names for what is in my case but it outputs the same 100 plus filesize

  


• Different filesizes for images generated using octave and python

  22 février 2017, par Lakshay Garg

  I am using python (scikit-image) and octave to generate 200 images as follows

  Python3

  import numpy as np
  
  from skimage.io import imsave
  
  
  
  images = [255*np.ones((100,100), dtype=np.uint8),  # white
  
               np.zeros((100,100), dtype=np.uint8)]  # black
  
  
  
  for i in range(200): # save alternating black and white images
  
      imsave('%04d.png'%(i+1), images[i%2])

  Octave

  pkg load image;
  
  
  
  im1 = 255*ones(100,100); # white
  
  im2 = zeros(100,100);    # black
  
  for i=1:200
  
      name = sprintf('%04d.png', i);
  
      if mod(i,2) == 0
  
          imwrite(im1, name);
  
      else
  
          imwrite(im2, name);
  
      end
  
  end

  Next, I use ffmpeg to generate two videos (alternating white and black frames) from these two sets of images using the following command

  ffmpeg -r 10 -loglevel quiet \
  
         -i ./%04d.png -c:v libx264 \
  
         -preset ultrafast -crf 0 ./out.mkv

  1. Sizes of image files generated by both these codes are different.

     • Octave white : 192 bytes, black : 98 bytes
     • Python white : 120 bytes, black : 90 bytes

  2. Sizes of video files generated from these octave and python images are significantly different from each other.

     • Octave filesize : 60 kilobytes
     • Python filesize : 116 kilobytes

  Why do we have this apparently very strange behavior ?

  EDIT

  Since it was suggested that the behavior might be dues to octave and python using different bit-depths to store the images, I changes the octave code to use 8 bit numbers

  im1 = uint8(255*ones(100,100)); # white
  
  im2 = uint8(zeros(100,100));    # black

  and now the image file sizes are nearly the same

  • Octave white : 118 bytes, black : 90 bytes
  • Python white : 120 bytes, black : 90 bytes

  but the problem is still the same for video files, octave : 60K, python : 116K

• dashenc : allow assigning all streams of a media type to an AdaptationSet

  29 janvier 2017, par Peter Große

  dashenc : allow assigning all streams of a media type to an AdaptationSet
  Using the characters "v" or "a" instead of stream index numbers for assigning
  
  streams in the adaption_set option, all streams matching that given type will
  
  be added to the AdaptationSet.
  Signed-off-by : Peter Große <pegro@friiks.de>
  
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavformat/dashenc.c