GB1465379A - Chroma keying video colour signals - Google Patents

Abstract

1465379 Colour television systems ROBERT BOSCH GmbH 4 Dec 1974 [8 Dec 1973] 52393/74 Heading H4F The switching signal for chroma keying video colour signals when a selected colour tone occurs is produced by an arrangement including two comparators and a matrix which generates two colour difference signals from the colour signals of a given colour source, e.g. a colour camera. The comparators receive respective colour difference signals and respective corresponding reference signals representing the selected colour tone, each feeding an AND gate which delivers the switching signal. The comparators may have one or two thresholds. Fig. 1 illustrates one embodiment of the arrangement. Matrix 9 may be fed by one of the cameras 1, 1<SP>1</SP> and provides the colour difference signals. Unit 13 may include a joystick control bar coupled to the wipers of potentiometers (Figs. 2-4, not shown) such that the two reference signals depend upon the orientation and tilt of the bar. When the difference of the signals fed to a comparator 10 or 11 exceeds a certain value, or lies in a certain range of values in the case of two thresholds, it sends a signal to gate 16 which controls switch 3 to select the output of one of the cameras.