GB1530448A - Pal system colour video signal reproducing system - Google Patents

Abstract

1530448 Colour television NIPPON VICTOR KK 31 Oct 1975 [5 Nov 1974] 45560/75 Heading H4F In slow motion replay of a PAL video signal, recorded on tape (Fig. 2, not shown) so that chroma signals of different kinds (i.e. wherein the phase alternating sub-carrier of one signal is phase reversed with respect to that of the other signal) are aligned side by side in adjacent tracks, the scanning head does not follow a single track, but passes from one to the next and as it does so the phase of one of the sub-carriers being detected is reversed, which leads to loss of colour in the reproduced picture. This is overcome by detecting when the phase alternating subcarrier has the wrong phase (by generating a half-line frequency signal, from the line sync., at the output of 43 and phase comparing it at 52 with a signal resulting from comparison at 50 of the colour burst phase with a reference 4À43 MHz signal from oscillator 63, the normal half-line periodicity of the latter being interrupted when said phase alternating subcarrier has the wrong phase) and substituting at switch 46, during these times, a signal which has the same frequency as the reproduced chroma signal but which has been phase corrected at 47. Alternatively (Figs. 6, 8, not shown) the substitute signal may be derived from the reproduced signal by a one line delay. Also described (Fig. 3, not shown) is a system wherein the recorded signal comprises a frequency modulated luminance signal and a chroma signal having a subcarrier frequency below that of the luminance signal.