Description: takes one or two strips as input key away a given color 
Description: (make it black and transparent or replace it by another image) 
Description: setting the tolerance to 0 only makes pixels, which exactly 
Description: match the given values for Y, U and V, transparent.  setting 
Description: it to 255 makes all pixels transparent.
Author:Daniel Dunbar 
Email: zr@blender.nl 
Website: http://www.geocities.com/evilzr
License: GNU