| 摘要 |
PURPOSE:To secure the correct result of discrimination of chrominance signals without effect due to a fact that the level of a marker M showing the type of a chrominance signal C becomes obscure temporarily or dropped out, by detecting the discordance of contents between a reference chrominance signal and an input chrominance signal in a prescribed number of horizontal synchronizing sections and then charging and controlling the contents of the reference chrominance signal so as to obtain the coincidence with said input chrominance signal. CONSTITUTION:As shown in the diagram, a chrominance signal discriminnating circuit 45 compares a reproduction/demodulation signal RVIN with a reference level signal VREF through a level comparator 51. When the change of a color latch output CRH caused every one H is not coincident with the change of the logic level of a chrominance discrimination output signal CD caused every one H, the output EQ of a coincidence deciding circuit 61 rises up to logic H. Thus a discordance cycle counter 63 is not cleared any more and starts counting horizontal synchronizing signals HD. Then the signal CD is delivered with repetitive inverting actions at a logic level different from the output CRH. In case the abnormality of the signal RVIN lasts over a prescribed section, the contents of the signal CD are immediately inverted. Thus it is possible to obtain the signal CD showing the signal RVIN. |
