JPS6444695A - Video signal processor - Google Patents

Abstract

PURPOSE:To prevent deterioration in the S/N of a chrominance signal in case of digital conversion by controlling the amplification factor of an amplifier based on the result of detection of the amplitude level of a burst signal by a detection means and inputting the burst signal to an analog/digital converter after the amplification factor of the burst signal period of the amplifier when the level of the burst signal is a prescribed level or below. CONSTITUTION:A burst level detection circuit 9 uses a burst gate pulse to extract only a burst signal from a color television signal so as to detect whether the level of the burst signal is larger or smaller than the prescribed level. A burst gate output circuit 13 inhibits the output of the burst gate pulse to the amplifier 6 when the level of the burst signal is larger than the prescribed level. When the level of the burst signal is smaller than the prescribed level, a burst gate pulse is outputted to the amplifier 6. The burst pulse is fed to a control input terminal 14 of the amplifier 6 and when the level reaches a 1st level, the gain of the amplifier 6 is larger for a period while the burst signal exists more than the other period to decrease the level of quantization noise.