Abstract: An improved video signal processing circuit (63) in the high quality television system for alternating-current driving a liquid crystal module (64) is disclosed. A reference signal is inserted into vertical blanking periods of a R signal by a reference signal generator (20) and switching circuit (4). The R signal in which the reference signal is inserted in converted into digital signals of n channels by an A/D converter (6). There exists difference in circuit characteristics among signal processing circuits for processing the respective digital signals. However, the signals signal-processed for each channel are supplied to microcomputer 21 through switching circuits (18.sub.1 -18.sub.n). Since the microcomputer 21 controls full scale level and offset level of D/A converters 9.sub.1 -9.sub.n and adders 11.sub.1 -11.sub.n, the deviations produced among sampled video signals due to difference in circuit characteristics among channels can be reduced.