GB1482079A - Method of transmitting colour television signals and apparatus for use in the method - Google Patents

Abstract

1482079 Colour television BRITISH BROADCASTING CORP 19 Sept 1974 [5 Oct 1973] 46706/73 Heading H4F An NTSC or PAL composite colour television signal at input 12, Fig. 1, is separated (decoded) in dependence upon frequency 14 into a predominantly luminance component and a predominantly composite chrominance component which is demodulated 16, for transmission over respective channels 32 and 34 of a transmission link 30, in such a manner that the composite signal can be accurately reconstituted by a coder 40. The separation is effected by accurately applying the function used to generate one of the separated components in inverse form in the generation of the other separated component, e.g. remodulating 18 the demodulated chrominance component and subtracting 20 it from the input composite signal to derive the separated luminance component. Demodulator 16 preferably provides a reference sub-carrier signal which is fed by a separate link to coder 40 so that remodulation 42 after transmission of the chrominance component is effected with the correct phase. In the coder 40 this remodulated chrominance component is added to the luminance component to form the composite signal. In a second embodiment (Fig. 2, not shown) demodulation of the chrominance component is effected before filtering thereof. In a third embodiment (Fig. 3, not shown) the filtered chrominance component is subtracted from the composite signal to form the separated luminance component. In a fourth embodiment (Fig. 4, not shown) the filtered luminance component is subtracted from the composite signal to form the separated chrominance component which is then demodulated, and in a fifth embodiment both the luminance and chrominance components are derived using filters having inverse filtering functions.