In a method of and an arrangement for inserting a background signal into parts of a foreground signal fixed by a predetermined key color, in which a control signal is derived from the foreground signal, this control signal assuming a first value when the foreground signal represents a color in the region...http://www.google.com.au/patents/US5381184?utm_source=gb-gplus-sharePatent US5381184 - Method of and arrangement for inserting a background signal into parts of a foreground signal fixed by a predetermined key color
