Color Decoding a PCM NTSC Television Signal

Abstract

Several techniques are developed for digital color decoding of NTSC television signals pulse-code modulated at 10.7-MHz rates (three times the color subcarrier frequency) and 14.3-MHz rates (four times the color subcarrier frequency). Digital comb filtering is also explored as a way to achieve superior color decoding. Encoding PCM NTSC television at the 14.3-MHz rate was found to afford the best algorithms for color decoding. A different PCM technique called Phase Alternating Line Encoding (PALE) permits encoding at 10.7 MHz and allows effective digital comb filtering and good color decoding. In the PALE technique, the phase of the 10.7-MHz digital encode command signal is inverted on adjacent television lines. Straight PCM encoding at 10.7 MHz is a poor third choice for comb filtering and color decoding applications.