| 摘要 |
PURPOSE:To suppress cross color below the specified value by controlling a band pass width to maintain an inter-polarity frame reverse frequency of an output of band pass filter circuit over the specified value. CONSTITUTION:This circuit provides a wide-band band pass filter circuit (wide- band BPF) 1a and narrow-band pass filter circuit (narrow-band BPF) 1b which extract a color signal from an NTSC image signal supplied to an input terminal IN, and a lower band pass filter circuit (LPF) 2 which extracts an luminance signal. In case there is coincidence of polarity more than n times during a polarity bit of the inter-frame is compared N times, namely, when a reverse frequency of the inter-frame polarity bit is below (1-n/N), a leakage amount of the luminance signal is decided that it is over the specified permissible range and an output of the narrow band RPFIb is selected. Another case, it decided that the leakage amount of luminance signal is within the permissible range and an output of wide-band BPFIa is selected. A band width of narrow-band BPFIb is set which it restricts the leakage amount of the luminance signal below approximate n/N. Consequently, the leakage amount of the luminance signal is maintained usually below the specified value.
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