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• FFMPEG Wrong color space with ProRes 4444 [closed]

  6 février 2020, par Mirza Kadic

  I’m unable to convert a video with ffmpeg in codec ProRes 4444 without color shift (something to do with colorspace). If I do quicktime png, color space stays the same, no problems with that.
  The only thing that fixes this is -vf colormatrix=bt601:bt709, but then I loose alpha channel, which I need of course.
  Any help would be appreciated.

• Google Lato Font Display discrepancies between platforms/software [closed]

  5 juin 2024, par CRAIG

  Using Google's Lato font with 400 weight, is giving me some inconsistent results between Photoshop/Web on MacOS and Linux Imagemagick & Linux ffmpeg.

  


  I have printed out some text on my linux server using the font using both imagemagick (v6.9.10-68) and ffmpeg's (v6.0) drawtext feature and in both cases, I get some extra space between the T and the e. (Image below)

  


  At first I was only testing ffmpeg and thought it was related to drawtext, but now that imagemagick is doing the same, I am thinking it may be somehow related to how the server is managing the font ?

  


  I did download the exact same font to test on my Mac and installed it, but I still get the original photoshop results I was getting before. So I don't think it is inherently the font unless I missed a step. I did completely uninstall the font and then install the downloaded one to be sure.

  


  However, the same word, font, font-size combo used in Photoshop and on the web does not produce the same space between the T and the e.

  


  Here is an image I put together showing the results :

  


  

  


  For reference, here is the imagemagick command :

  


  convert -size 900x900 xc:black -font /fonts/Lato:400.ttf -pointsize 261.6 -fill white -gravity center -annotate +0+0 'Text' testoutput.png

  


  And the ffmpeg command :

  


  /usr/local/bin/ffmpeg -f  lavfi  -i  color=c=black@0.0:s=953x953:r=30:d=5,format=rgba  -filter_complex  "drawtext=expansion=none:enable='between(t,0,5)':fontfile='/fonts/Lato\:400.ttf':fontcolor=0xffffffff:fontsize=294:text='Text':x=(w-text_w)/2+0:y=476.5-(max_glyph_a)+(294/2.8)"  -copyts  -threads  1  -c:v  png  -pix_fmt  rgba  -movflags  faststart  -r  30  -t  8  -y  testoutput.mov

  


• FFMPEG Determine average color of an area of a video

  12 novembre 2019, par Naved Khan

  I have a use case where I’d want to insert one of two watermarks - one designed for a dark-ish background, the other for a light background into a video. Let’s say that I’d want to do this on the top right corner of the video.

  How do I determine the average color of the top right section of the video ? Post this, how do I determine which watermark to use by looking at the average color ?

  I have a solution right now where I am taking equally spaced screenshots and then measuring the average color, but it’s excruciatingly slow, especially for longer videos.

  # Calculate average color
  
      black_distances = []
  
      white_distances = []
  
  
  
      movie = FFMPEG::Movie.new(video_file)
  
      (0..movie.duration / 10).each do |second|
  
  
  
        # extract a frame
  
        filename = "tmp/watermark/#{SecureRandom.uuid}.jpg"
  
        movie.screenshot filename.to_s, seek_time: second
  
  
  
        # analyse frame for color distance
  
        frame = MiniMagick::Image.open(filename)
  
        frame.crop('20%x20%+80%+0')
  
        frame.resize('1x1')
  
        pixel = frame.get_pixels.flatten
  
  
  
        distance_from_black = Math.sqrt(((black[0] - pixel[0])**2 + (black[1] - pixel[1])**2 + (black[2] - pixel[2])**2))
  
        distance_from_white = Math.sqrt(((white[0] - pixel[0])**2 + (white[1] - pixel[1])**2 + (white[2] - pixel[2])**2))
  
  
  
        black_distances.push distance_from_black
  
        white_distances.push distance_from_white
  
  
  
        File.delete(filename) if File.exist?(filename)
  
      end
  
  
  
      average_black_distance = black_distances.reduce(:+).to_f / black_distances.size
  
      average_white_distance = white_distances.reduce(:+).to_f / white_distances.size

  I am also confused about how to use the resulting average_black_distance and average_white_distance to determine which watermark to use.