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• 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

• Adding subtitles to video using Laravel FFMpeg

  13 juin 2024, par Pieter van der Mullen

  I've been trying to convert my console command to work with the Laravel FFMpeg package. The issue that I've been running into is that the available Filters are not really well documented.


  This is the Laravel code that is not working. The only part that does not work is the last addFilter part with the srt and font file.

  


              FFMpeg::fromDisk('local')
            ->open([$backgroundImage, $audioFile])
            ->export()
            ->toDisk('local')
            ->addFilter(function (FrameFilters $filters) {
                $filters->custom('scale=1920:1080');
            })
            ->addFormatOutputMapping(
                new X264,
                Media::make('local', $newVideoPath),
                ['0:v', '1:a']
            )
            ->addFilter(function ($filters) use ($srtFile, $fontFile) {
                $filter = "pad=1920:1080:0:0:color=black,subtitles={$srtFile}:force_style='Fontname={$fontFile},Alignment=10,Fontsize=36,BorderStyle=3,Outline=1,OutlineColour=&HFFFFFF&,PrimaryColour=&H008d7f00&'";
                $filters->custom('0:v', '0:v', $filter);
            })
            ->save();


  


  The command which I used to use in the console using Symphony Process was :

  


  '-vf', "pad=1920:1080:0:0:color=black,subtitles=$srtFile:si=0:force_style='Fontname=$fontFile,Alignment=10,Fontsize=36,BorderStyle=3,Outline=1,OutlineColour=&HFFFFFF&,PrimaryColour=&H008d7f00&'"


  


  Is there anyone who has experience doing this ?

  


• HEVC File bigger after converting from h264

  26 janvier 2019, par Aaroknight

  I’m currently working an an automated Python script for indexing and converting all my movies and episodes with ffmpeg. I use subprocess.call() for running the ffmpeg command and tested this command with some movies. As expected the big h264 files were converted to merely one third of what they used to have.

  But now that I was testing the method I found that a converted episode (about 400MB in h264) had over 1,6GB in hevc. I have absolutely no idea why the new file would be that much bigger in hevc.
  This is my code :

  def convert(path):
  
      outvid = path.strip(".mkv") + "h265.mkv"
  
  
  
      cmd = ["ffmpeg", "-i", path, "-map", "0", "-map_metadata", "0", "-map_chapters", "0", "-c:v", "libx265",
  
             "-c:a", "copy", "-c:s", "copy", "-preset", "ultrafast", "-x265-params", "lossless=1", outvid]
  
      subprocess.call(cmd)
  
  
  
  convert("/Volumes/2TB/Black Butler/Season 1/Black Butler S01E01.mkv")

  I don’t have that much experience with ffmpeg, nor with subprocess. This is one of my first bigger projects. I hope someone can tell me what the problem might be.

  UPDATE
  Problem applies only for small video files. I now just check for the file size and skip the small files. Wouldn’t have made much of a difference anyway.