A digital video key signal generator for digital video special effects uses two cascaded programmable lookup tables 20, 24. One table 20 is addressed by the two chroma component signals and the second table 24 is addressed by the luma signal and the output of the first table. The generator is particularly suitable for use with CCIR Rec. 601 digital signals, and can be used for a wide variety of compositing functions, using luma keys, chroma keys, combinations thereof, and multiple chroma keys simultaneously. <IMAGE>
Digital colour video key signal generator using two programmable lookup tables