DIGITAL NTSC VIDEO SIGNALS

摘要

A component of an NTSC color television signal, e.g. the luminance component, is digitally sampled by sampling an input signal with a mean frequency related to the color subcarrier frequency, e.g. 2fsc, and changing the sampling phase between successive lines of a field by an amount equal to half the interval between samples. The sampling pattern repeats every four fields, and the sampling phase changes by 180 DEG between corresponding points on adjacent pictures. The phase shift between fields (1 and 2) of the four-field structure can be +90 DEG and the phase shift between fields (3 and 4) can be -90 DEG , or vice versa. This can be used in a coding method which involves sub-band analysis filtering the luminance input video signal into a low-frequency luminance signal and a high-frequency luminance signal, sub-band synthesis filtering the high-frequency luminance signal and the chrominance input video signal to form a combined high-frequency signal, and phase-segregated coding the low-frequency luminance signal and the combined high-frequency signal to provide the composite video output signal.