DPCM Quantization of Color Television Signals

The application of DPCM to the coding of color television signals calls for the design of the quantization characteristics for the luminance and the two color difference components. In this paper we describe quantizer designs based on visibility thresholds of quantization noise measured as a function of prediction error for a number of test slides. We assume a quantizer for the luminance component designed previously by a similar procedure and conduct psychovisual tests for the U and V color components. The results show that, mainly for granular noise, there is some visual superposition of quantization noise between the luminance and the U chrominance signals, while little or no visual interaction is evident between the luminance and the V signal impairments. The quantizers for the U and V components are designed such that, with the previously designed luminance quantizer, the number of levels are minimized without exceeding the visibility thresholds. We conclude that a total of 6 bits per color sample are required to code the U and V components together at 4.4 MHz.