| 摘要 |
PURPOSE:To prevent the deterioration of S/N and to reduce level fluctuation of an input carrier chrominance signal in the standard mode reproduction and long time mode reproduction by using most suitably the effective dynamic range of input of an A/D convertor. CONSTITUTION:Low frequency conversion carrier chrominance signals inputted from a terminal 11 are adjusted in level by a controlling signal in a gain control amplifier 12 and outputted to an A/D convertor 13. The signals digitalized by the A/D convertor 13 are converted to two color difference signals, B-Y and R-Y, by a comb line filter 19. These color difference signals are added to data 1H before, and after removing crosstalk, modulated by a modulator. A color difference signal B-Y during burst period is outputted by a burst level detector 22, and this is compared with the reference level by a comparator 23, and consequently, gain of the gain control amplifier 12 is controlled. At this time, by making the reference level different in standard reproduction mode and long time mode, an effective dynamic range most suitable for each mode can be obtained. |
