Facsimile and static presentation processing – Static presentation processing – Attribute control
Patent
1991-08-15
1993-08-03
Chin, Tommy P.
Facsimile and static presentation processing
Static presentation processing
Attribute control
358 27, 358 28, H04N 964
Patent
active
052334104
ABSTRACT:
An interpolating digital signal clipping circuit provides pre-clipping of the luminance component of a video signal. A difference circuit adjusts each sample so that a single bit indicates whether the sample value is closer to a positive or negative clipping limit. Interpolated samples are produced by phase shifting FIR filters and are applied, along with the actual current sample, to a minimum or maximum selecting circuit that selects the minimum or maximum sample depending on the state of the indicating bit. The selected sample is compared with the clipping limits to produce an excess signal that indicates how much the selected sample exceeds the relevant clipping limit. A gain control signal is generated to be a "1" when no clipping is required and less than one when clipping is required. A digital video signal clipping circuit receives this pre-clipped luminance signal and adjusts each sample as above. Multipliers square the chrominance components, and an adder adds the squares and applies the output as addresses to a memory that produces a chrominance magnitude signal. The chrominance magnitude signal is combined with the adjusted luminance signal to obtain a composite magnitude signal. Again, a gain control signal is generated that is a "1" when no clipping is required and less than one when clipping is required, and this signal is used to reduce the video components before they are combined into a clipped composite video output.
REFERENCES:
patent: 4949177 (1990-08-01), Bannister
patent: 4953008 (1990-08-01), Kaye
patent: 4987482 (1991-01-01), Imai
Chin Tommy P.
Smith-Hill John
The Grass Valley Group Inc.
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