GB1453588A - Colour television system - Google Patents

Abstract

1453588 Colour television DECCA Ltd 19 Sept 1974 [28 Sept 1973] 45582/73 Heading H4F To improve the vertical definition of the luminance component of a television signal which is obtained by decoding a luminance signal and a line-sequential chrominance component (R-M, G-M, B-M) of lesser bandwidth than the luminance signal a decoder is provided which is arranged to compare each line of an input signal with an earlier line of corresponding chrominance and reduced definition in order to derive signals which denote vertical luminance transitions. As shown in Fig. 1 a video signal, e.g. from a video-disc player, is fed to input 10 and via compensating delay 11, series connected one line period delay lines 14, 15 and 16 having a feedback loop to an adder 13 including an amplitude reducing device, e.g. an amplitude halver as shown, adding and subtracting stages 17-22, and low pass filter 23 to an adder 12. In addition the inputs of delay lines 14-16 are tapped off to a set of commutating switches 24 which provide low-frequency continuous chrominance components (R-M), (G-M) and (B-M) to separate channels, matrices 25 to 26 forming a composite output signal. In this arrangement the output of adder 13 comprises luminance components denoting vertical transistions. The outputs of adders 17 and 18 comprise luminance signals of low definition which are combined with the input signal at input 10 to produce at the output of adder 22 a chrominance signal combined with spurious edge signals so that the output of adder 12 comprises the input luminance of full band-width together with some spurious, band-width restricted, signals which produce, subsequent to a sharp vertical luminance transition in a picture obtained at a receiver, a ringing or oscillation. A second embodiment of the decoder is described with reference to Fig. 2. An encoder, Specification 1,453,589, for use with the above decoder which reduces the luminance ringing thereof and preferably also reduces the vertical definition of each of the line sequential chrominance components, comprises as shown in Fig. 3 a series of one line period delay lines 31-36 to which a luminance signal is applied, processed 37-41 as shown and added 47 to a line-sequential chrominance signal from processor 30. To reduce the vertical definition of the chrominance components the processor 30 Specification 1,453,590, includes a series arrangement of six one line period delays and appropriate summing amplifiers (Figs. 4 and 5, not shown).