Patent ID: 6803965
Filing Date: 2004-10-12
Classification: H04N

Abstract:
A method of measuring horizontal frequency, which comprises the steps of;resetting an N-bit counter (N is a positive integer), which is operative to count pulses constituting a horizontal synchronous signal separated from a video signal, at a time point corresponding to a front or rear edge of a vertical synchronous signal separated from the video signal, causing a data latch portion, which is operative to latch selectively count data obtained from an M-bit counter (M is a positive integer) operative to count clock pulses having a predetermined frequency, to latch the count data obtained from the M-bit counter at a time point corresponding to a front or rear edge of a bit output signal obtained from a predetermined bit position of the N-bit counter, detecting a period which corresponds to X times (X is a positive integer) a horizontal period of the video signal based on a difference between counted values represented respectively by a couple of count data latched successively by the data latch portion, and measuring horizontal frequency of the video signal by calculating the horizontal frequency on the strength of the period corresponding to X times the horizontal period of the video signal.