title: FFMPEG: Making a specifc range of color pixels transparent
body: <p>I am trying to overlay one video on top of another using ffmpeg, but couldn't quite understand the error.
  I based on the existing command from <a href="https://stackoverflow.com/a/38581696/5103681">here</a></p>
  
  <p>More specifically, I want to replace the all colors close to a specific color (say brown r:82,g:44,b:11), and then have them set as transparent.</p>
  
  <pre><code>ffmpeg -i moonmen.mp4 -i transparent_overlay.mp4 -filter_complex
  "[1]split[m][a];
   [a]geq='if(between(r(X,Y), 77, 87)*between(g(X,Y), 39, 49)*between(b(X,Y), 06, 16) ,255:255:255,0:0:0)';
   [m][al]alphamerge[ovr];
   [0][ovr]overlay"
  output.mp4
  </code></pre>
  
  <p>but I got error:</p>
  
  <pre><code>[Parsed_geq_1 @ 0x7fc8e2e08400] Either YCbCr or RGB but not both must be specified
  [AVFilterGraph @ 0x7fc8e2e07c60] Error initializing filter 'geq' with args 'if(between(r(X,Y), 77, 87)*between(g(X,Y), 39, 49)*between(b(X,Y), 06, 16) ,255:255:255,0:0:0)'
  Error initializing complex filters.
  Invalid argument
  </code></pre>