| 摘要 |
PURPOSE:To upgrade the dignity of a reproduced picture by detecting the transi tion of an original video signal, slanting the transition segment of a chrominance signal or a low-band-convertion chrominance signal separated based on the detection signal slightly so as to suppress a mixed modulation and inversion phenonenon. CONSTITUTION:When an original video signal is supplied to a band-pass filter 21, a carrier chrominance signal is obtained from the filter 21. This carrier chrominance signal undergoes a detector 22, a differentiating circuit 23, and a both waves rectifying circuit 24, and is made to a transition-detecting pulse which is not time-shifted from the original video signal. This pulse is elongated and made to a pulse train having a prescribed pulse width by a sample holding circuit 25, undergoes a delay circuit 26 and a low-pass filter to become a control pulse train leading and trailing slightly as peaks having the respective transition points of chrominance signals. A voltage controlling amplifier(VCA) 17 modulates the amplitude of a low-band-convertion chrominance signal c1 from a chrominance signal processing circuit 13 by using the above-mentioned control pulse train. Consequently, the low-band-convertion chrominance signal outputted from the VCA 17 comes to have a slightly slanted transition segment.
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