Constant luminance tint reference
AssigneeGTE Products Corporation
InventorPaul G. Wolfe
Life of this patent
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Abstract
In a VIR-responsive Tint Control system a dematrixing circuit for synthesizing, from the individual chrominance demodulator outputs, a ZERO-COLOR reference signal. The VIR chrominance interval signal and the ZERO-COLOR reference signals are used as input to a feedback loop that also includes the receiver's chrominance subcarrier oscillator. By comparing the VIR chrominance interval signal to the synthesized ZERO-COLOR reference subcarrier oscillator phase errors are corrected by virtue of a single sampling of the VIR signal.
Claims8
In a VIR-responsive tint control circuit that effects accurate phasing of the chrominance subcarrier oscillator by comparing one output of the chrominance demodulator during the chrominance reference portion of the VIR signal to a ZERO-COLOR reference signal indicative of an absence of color information, the improvement comprising:
- dematrixing means for synthesizing from the chrominance demodulator outputs an appropriate ZERO-COLOR reference signal whereby only one sampling of the VIR signal need be taken in order to effect desired tint control.
A VIR-responsive tint control circuit comprising:
- a demodulator for demodulating the chrominance signal and providing separate (B-Y), (G-Y) and (R-Y) outputs,
- a subcarrier oscillator having an output coupled to the demodulator and a Tint Control terminal;
- dematrixing means having an input coupled to the demodulator outputs for synthesizing a ZERO-COLOR reference signal;
- a gated buffer having a signal input coupled to the (R-Y) output of the demodulator and an enabling input coupled to a source of chrominance reference interval pulses, and
- an error amplifier having a first input coupled to the output of the gated buffer, a second input coupled to the dematrixing means and an output coupled to the Tint Control terminal for developing a Tint Control signal in response to the difference between the (R-Y) output of the demodulator during the chrominance reference interval of the VIR signal and the ZERO-COLOR reference signal.
Dependencies are inferred from the claim text.