JPS6439877A - Video signal processing circuit - Google Patents

Abstract

PURPOSE:To prevent the change of a black level due to the change of picture quality control by inputting a video signal, whose picture quality is controlled, to a black level control circuit and after through a low-pass filter, inputting it to a black level peak hold circuit. CONSTITUTION:The video signal, whose picture quality is controlled, is inputted to a black level correcting circuit 13 and after a black level correcting is executed, it is outputted to a terminal 11. The black level correcting circuit 13 is composed of a black level control circuit 6, which executes the level shift of the video signal or the gain control of the black level, and a black level peak hold circuit 7 to detect a black peak with a filter which is constituted from a low-pass filter 12, a resistance 8 and a capacitor 9. For the output of the black level control circuit 6, the black level is detected through the low-pass filter 12 by the black level peak hold circuit 7. The output is fed-back to the black level control circuit 6 and a black level correcting is executed. Thus, the black peak of an outline correcting signal is not held and the change of the black level due to the change of the picture quality control is prevented.