MODIFIED CHROMA KEYED TECHNIQUE FOR SIMPLE SHAPE CODING FOR DIGITAL VIDEO

An efficient chroma key-based coding technique for digital video with an optimized switching threshold. An optimized binary keying threshold is provided for switching between a first image region (such as a background region) and second image region (such as a foreground object) video picture. The threshold optimizes a PSNR of a quantization error Q of a key color K. A chroma key technique is also provided for representing the shape of a video object, where the shape information (alpha plane) of a foreground object is embedded in the keyed output, so there is no need to carry an explicit alpha plane, or use alpha plane coding. The chroma key shape representation technique provides a smooth transition at the boundary between objects without the need for special switching patterns, such as a general gray scale shape coding tool, or post-processing, e.g., using feathering filters.