Chrominance signal processing system.

摘要

A digital chrominance signal processing system performs control in such a manner to make the phase difference between the burst signal and the clock always zero and comprises: an A/D converter (11) for effecting analogue/digital conversion of a video signal containing a carrier chrominance signal; a frequency controllable variable frequency oscillator (24) for generating a clock to be given to said A/D converter; a phase comparator (13) for comparing the output of said A/D converter with the phase of said clock; a computing circuit (14) for computing the absolute value and sign of the output signal of said phase comparator during a burst period; and two current sources (18,19) of current outflow type and current influx type whose current values are controlled by the absolute value output (16) of said computing circuit (14) and turned on/off respectively by the sign output (15) of said computing circuit (14), wherein output terminals of said current outflow type current source and said current influx type current source are connected with each other and outputs of said current sources control said variable frequency oscillator through a low pass filter (22,23).