| 摘要 |
PURPOSE:To simplify the clamp voltage adjustment of clamp circuit of the subsidiary screen and to execute the complete DC reproduction of the screen, by providing clamp circuit, A/D converter, memory circuit, pedestal data pick-up circuit, data holding circuit, memory control circuit, switching circuit, and D/A converter. CONSTITUTION:Y signal, color difference signals R-Y, B-Y, which are each clamped at proper clamp voltage are A/D converted by A/D converters 19, 20, 21. The Y signal is converted into PCM signal by the A/D converter 19, and written on a memory circuit 22 by a memory control circuit during the time when the subsidiary screen is valid. The Y signal written on the memory circuit 22 is compressed along the time axis and read out to the area which display the subsidiary screen according to the synchronization signal separated by a synchronization separation circuit 6 of the parent screen. Similarly to Y signal, the color difference signals R-Y, B-Y synthesize the pedestal data with the time-axis-compressed output data of memory circuit 23 and memory circuit 24 by switching circuit 47, 48.
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