VIDEO SIGNAL PROCESSING

摘要

A method and apparatus for keying digital colour TV signals to avoid "stairstepping" of pixels at the edges of the key whilst retaining a hard switch between the keyed scenes. This is achieved by comparing successive digital keying signals with a desired digital clip level. In the event that the clip level occurs between two successive digital signals an interpolation of the clip level between these is created fractionally. A digital representation of this fraction is then included in the keying signal so that keying is accomplished on a subpixel basis without actually increasing the frequency of sampling.