JPH0441389B

PURPOSE:To enable to precisely generate a reference signal by obtaining a multivalued signal including the binary signal of a digital video signal compared with the reference signal. CONSTITUTION:A digital video signal V1 outputted from an A/D converter 1 is supplied to ROM as a comparing means outputting a multivalued signal V0 by comparing the reference signal of a reference signal generating part 2 with a digital video signal. The reference signal generating part 2 has a function to generate a reference signal Vr which changes following a digital video signal V1, and is composed of ROM4, 7 and 10, a latch 5, an AND gate 6, a counter 8 and an invertor 9. A digital video signal Vi and an output signal Vr1 which is made clear by the later explanation are given to ROM4, and the reference signal Vr is outputted by ROM3 as shown in the right formula under the following relational expression based upon the relation of the size of the digital video signal Vi and the output signal Vr1.