VIDEO SIGNAL PROCESSOR AND DISPLAY SYSTEM

摘要

PROBLEM TO BE SOLVED: To automatically adjust the sampling phase to an optimum value in the case of A/D-converting a video signal. SOLUTION: An input video signal VO representing a black/white level two- gradation test pattern is converted into 8-bit data at an A/D converter 4 synchronously with a sampling clock generated by a write control circuit 5 and the converted data are stored in a memory 6. An MPU 9 reads data of picture elements for a valid period of a video signal stored in the memory 6, calculates a difference AT between a mean value of white level picture element data larger than a prescribed value and a mean value of black level picture element data smaller than a prescribed value a sum VT between a variance of the white level picture element data and a variance of the black level picture element data and controls a phase of the sampling clock generated by the write control circuit 5 so as to maximize the AT and to minimize the VT.