| 摘要 |
PURPOSE:To compose a picture changing variously according to the status of an input color video signal by extracting the bright component of the input color video signal, discriminating the component in a signal level and generating a video keying signal from the result of the discrimination. CONSTITUTION:Signals A, B applied to video input terminals 1, 2 are digitized through A/D converters 4, 5 respectively and sent to a multiplexer 9. In case of the signal A, its chrominance component is removed from the signal A through a low pass filter 6 and only the lower 6 bits are sent to a comparator 7 while ignoring the upper 2 bits. In case of a control voltage signal from a variable resistor 11, 6 bits of the signal are quantized by an A/D converter 8 and sent to the comparator 7 to compare the quantized signal with the signal passed through the filter 6. The output of the multiplexer 9 is selected according to a signal outputted from the comparator 7 and the color video signals A and B are mixed. The mixed signal is returned to the original analog signal by a D/A converter 10 to output it. |
