Abstract: By reducing the saturation (amplitude) at changes in the hue (phase) of the chrominance subcarrier of a video signal, the phenomenon of "dot crawl" can be substantially reduced for graphic data. It has been found that large hue (phase) changes associated with graphic data can cause large frequency shifts of the chrominance subcarrier resulting in a substantial portion of the chrominance subcarrier being unsuppressed by the chrominance subcarrier rejection filter of the luminance decoder. By reducing the saturation during the hue transition, the intensity of the spurious luminance information of the non-suppressed chrominance subcarrier is reduced.

Abstract: In a video encoder, the color distortion between pixels can be reduced by encoding the hue transition to limit very large hue (phase) transitions and encode a corresponding smaller phase transition. This produces fewer spurious colors between pixels during the encoding. This can be done by comparing the change in hue value to a reference value and adding or subtracting 2 .pi. to this reference value to reduce the absolute value of a modified delta hue signal.