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 or picture of a PAL color television signal is stored in a store and provides a signal at an input (52). The stored signal consists of 2fsc samples taken at 45 DEG to the U-axis. The signal is separated by a filter (56) and subtractor (58) into a high frequency or chrominance signal and a low frequency or luminance signal. The chrominance signal is delayed by delay means (62) such that the chrominance components of two lines which are an odd number of lines apart are made available simultaneously. These signals are combined by switches (S1, S2) and/or combining circuits (68) to provide a signal at 4fsc which is combined with the luminance signal in a combining circuit (70) to provide a 4fsc PAL output (72). The manner of the combination of the chrominance components is changed on an 8-field cycle. In an alternative arrangement, if the PAL signal is originally stored in a store which provides outputs from more than one line simultaneously, two stored lines can be combined, and the chrominance portion of the thus-combined signal combined with the luminance portion of a stored signal to provide the output.