Color television receiving system utilizing multimode inferred highs correction to reduce color infidelities

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 and luminance infidelities, such as incorrect or inverted highs, over-modulation and rectification which are visible in regions of sharp transitions from one color to another or in regions of concurrent high color saturation and significant high frequency detail. Such infidelities are substantially reduced by effectively supplementing either the chrominance or the primary color signals with inferred high-frequency chrominance components derived from signal information discovered to be inherently available in NTSC-type signals and their implicit constraints. Specifically, in one form of the invention it has been found that in regions of sharp color transitions and in regions of high color saturation, relevant high frequency chrominance components can be scaled from the high frequency portion of the received monochrome signals in accordance with different respective scaling algorithms. A receiving system is provided with multimode inferred highs correction circuitry responsive to a received NTSC-type signal for automatically deciding which, if any, correction modes are appropriate for a given time and frequency region of the received signal and automatically enabling correction circuitry for providing the appropriate inferred high frequency correction signals.