| 摘要 |
Video disc player is provided with a sync separator which is responsive to output of luminance comb filter after de-emphasis circuit processing. Input to comb filter circuitry is provided by amplitude modulator, responsive to carrier wave oscillations from a voltage controlled oscillator (VCO) and to composite video signals provided by a defect compensation system. The compensation system normally supplies an output directly derived from the player's pickup circuits, but, under defect conditions, substitutes stored video signals. The VCO is a component of a phase locked loop (PLL) arrangement, also including a burst gate for selectively passing color synchronizing information contained in the modulator output. Gating pulses for the burst gate are generated by apparatus responsive to the sync separator output, the generating apparatus including a capacitor charging circuit activated by the trailing edge of a separator output pulse to control gating pulse termination, and a separate capacitor discharging circuit activated by the trailing edge of a separator output pulse to control gating pulse initiation. Also responsive to an output of the sync separator is a keying pulse generator for controlling keyed clamping of the luminance comb filter output, with keying pulse timing determined by differentiated and integrated versions of the separator output. |
