GB1535721A - Television systems - Google Patents

Abstract

1535721 Television systems INDEPENDENT BROADCASTING AUTHORITY 1 Dec 1975 [31 Aug 1974] 31611/74 Heading H4F A digital video signal consisting of digital samples at intervals t is processed to provide a signal substantially free from the luminance component, or alternatively from the chrominance component, by an arrangement which includes a delay unit comprising a number of delays. At each interval t the delay unit provides simultaneously those samples which correspond to a rectangular array of picture points, the height of the array extending over at least two successive lines of the image represented by the video signal. These samples are weighted in multipliers and the weighted samples are summed. The weighting applied is such that, in the case of an array of points of uniform luminance, the chrominance component of the sum of the weighted samples is zero. Alternatively, in the case of an array of uniform chrominance, the weighting is such that the luminance component of the sum is zero. The delay unit may comprise 14 delays (Fig. 2a, not shown) to provide 15 simultaneous samples corresponding to an array 5 points wide by 3 lines high. The weighting values applied to the array are preferably symmetrical about the centre column and row of the array (e.g. as in Table 1 or Table 2, not shown), and the respective sums of the values in the other rows and columns are zero. If the array of weighting values is symmetrical some of the delays in the delay unit may be omitted, Fig. 2b (not shown). If the array of weighting values for extraction of the luminance component differs from that for the chrominance component respective multiplying and summing circuits must be used. However, if the arrays are the same, except for the centre value, a single such circuit may be used, the circuit being modified by the addition of a further multiplier and a subtractor to provide the components on respective outputs, Fig. 8 (not shown). Since the array of picture points may not have uniform chrominance or luminance the extracted components may not be entirely free of the other component, but the effect is stated to be of no significance. As disclosed the chrominance component is fed to I and Q demodulators whose outputs, together with components of the luminance component on three 120 degree axes, are time divisional multiplexed, Figs. 1 and 7 (not shown). The multiplexed signal may be added to another such signal to form a composite picture signal, or to signals derived from a set of lines of the picture via multipliers and an interpolator for the purposes of standards conversion.