title: FFMPEG detect color bars and tone in video
body: <p>I am trying to detect if a video has any valid content or is just the standard broadcasting bars &amp; tone.  So far I've looked at this question: <a href="https://superuser.com/questions/1036449/detect-color-bars-ffmpeg/1036478#1036478">https://superuser.com/questions/1036449/detect-color-bars-ffmpeg/1036478#1036478</a>
  which generates bars &amp; tone from the first frame and then compares that against the rest of the stream but in my case I need to run the ffmpeg command within a folder that only has one file that has already been found by my python script.</p>
  
  <p>Is it possible to use ffmpeg's blend=difference to check that a short bars &amp; tone clip is a subclip of one of my video files? I'm thinking of this in the same way you can check if a string is within a string, or is there a better way to check for bars that I'm not thinking of?</p>
  
  <p>Thanks!</p>