Add example of converting video with ffmpeg

README.md

@@ -141,6 +141,16 @@ shows a simple animation of a slowly beating heart on the first message, and a b
 
 ![M2 ishm](photos/m2ishm.gif)
 
+    ffmpeg -f lavfi -i 'cellauto=size=48x11:rate=10,setpts=10*PTS,format=monow,trim=end=123,        tile=123x1' gfx/cellauto_123.png
+    ffmpeg -f lavfi -i 'cellauto=size=48x11:rate=10,setpts=10*PTS,format=monow,trim=end=123,reverse,tile=123x1' gfx/cellauto_123_reverse.png
+    ./led-badge-11x44.py -m 5 -s 8 :gfx/cellauto_123.png:
+
+demonstrates how to convert video into compatible animation using ffmpeg, and possibly reverse it.
+(In this case, autogenerated animation of cellular automaton is used).
+Maximum number of frames permitted by current code is 123.
+
+![LED Mini Board](photos/ffmpeg_cellauto.gif)
+
     python3 ./led-badge-11x44.py --list-names
 
 prints the list of builtin icon names, including :happy: :happy2: :heart: :HEART: :heart2: :HEART2: :fablab: :bicycle: :bicycle_r: :owncloud: ::