In a video signal processing device, an input video signal VO representing a
test
pattern having two gradations of black and white is converted to 8-bit data by
an A/D converter 4 in synchronism with sampling clocks generated in a write-in
control circuit 5, and then stored in a memory 6. An MPU 9 reads
out picture element data in an effective area of the video signal stored in the
memory 6, and calculates the difference AT between the average value of
white-level picture element data whose values are larger than a predetermined value
and the average value of black-level picture element data whose values are smaller
than a predetermined value, and the total variance VT between the variance of the
white-level picture element data and the variance of the black-level picture element
data. The MPU 9 controls the phase of the sampling clocks generated in the
write-in control circuit 5 so that the AT is maximum and the VT is minimum.
With this operation, the sampling phase can be automatically adjusted to the optimum
value when the video signal is converted to digital data.
