METHOD OF AND APPARATUS FOR DERIVING A PAL COLOUR TELEVISION SIGNAL CORRESPONDING TO ANY DESIRED FIELD IN AN 8-FIELD PAL SEQUENCE FROM ONE STORED FIELD OR PICTURE OF A PAL SIGNAL

摘要

A single field of a PAL color television signal is stored in a store (50) and provides a signal at an input (52). The signal is delayed by one-line delays (56,58) in series to provide one and two-line delayed signals. Separate switching units (60,62) select desired ones or combinations of the input and delayed signals to constitute respectively the low-frequency and chrominance part of the signal at the output (82). The switch positions are changed between fields, and for at least some fields of the PAL sequence each component of the output signal is formed by combining signals from more than one line, i.e. a halving adder (64;66) averages successive lines for the low frequency part of the signal and a halving subtractor (68) forms the difference between lines two lines apart for the chrominance part. The selector unit outputs are combined in an adder (78) which receives the output of the first selector (60), and also the difference between the output of the two selectors after band pass filtering (76). The store (50) can be replaced by a random access store capable of outputting three successive lines simultaneously. The apparatus has special utility in equipment for movement portrayal.