midipipe midi youtube playback controller applescript. This one maps a continuous controller's value to the playback speed.

midipipe-youtube-midi-control-advanced.applescript

on runme(message)
  
  tell application "Google Chrome"
    
    if (item 1 of message = 191) then
      
      # Play or pause a video.
      repeat with t in tabs of windows
        tell t
          
          if URL starts with "http://www.youtube.com/watch" or URL starts with "https://www.youtube.com/watch" then
            if (item 1 of message = 191) and (item 2 of message = 117) and (item 3 of message > 0) then
              execute javascript "
			var v = document.querySelector('video');
			if (v.paused) {
			  v.play(); 
			}
			else { 
			  v.pause(); 
			}
	      "
            exit repeat             
            end if
            if (item 1 of message = 191) and (item 2 of message = 17) and (item 3 of message > 0) then
              
              set speed to (3 * (item 3 of message) / 127)
              execute javascript "
			var v = document.querySelector('video');
			v.playbackRate = " & speed & ";
              "
              exit repeat
            end if
          end if
        end tell
      end repeat
    end if
    
  end tell
end runme