COLOUR TELEVISION RECEIVING SYSTEM UTILIZING INFERRED HIGH FREQUENCY SIGNAL COMPONENTS TO REDUCE COLOUR IN FIDELITIES IN REGIONS OF COLOUR TRANSITIONS

摘要

A color television receiving system for NTSC-type signals is provided with signal processing circuitry and methods for reducing the visibility of color infidelities, such as incorrect highs, polarity reversals, and errors in visual luminance, which are visible in regions of sharp color transitions. Such infidelities are substantially reduced by effectively supplementing either the chrominance or the primary color signals with inferred high-frequency chrominance components which components are, respectively, processed from signal information discovered to be inherently available in NTSC-type signals and their implicit constraints. Specifically, it has been found that in regions of sharp color transitions, high frequency chrominance components can be scaled from the high frequency portion of the received monochrome signal in accordance with the respective ratios of the time rate of change of the received reduced bandwidth chrominance signal to the time rate of change of a comparable low frequency component of the received monochrome video signal. Alternatively, inferred high frequency primary color components can be analogously derived. A variety of specific circuit embodiments and methods can be used to process suitable inferred high frequency components.