US 6,188,788 B1Granted

Automatic color saturation control in video decoder using recursive algorithm

AssigneeTexas Instruments Incorporated

InventorsKarl Renner, Weider Peter Chang

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Abstract

A method for automatic color gain control utilizes a plurality of process blocks which compare the measured burst amplitude with an ideal burst amplitude, and then generate necessary scaling factors to automatically control the gain. Each of the process blocks utilizes recursive relationships for accumulating values, which recursive relationships require no multiplications but, rather, require only additions and/or subtractions, which additions and/or subtractions require merely an adder with a change of sign. A scale value is generated which represents the ratio of the measure to ideal burst amplitude value, which is then utilized to generate Cr and Cb in a YCrCb digitized format. This is utilized to scale the U and the V values in a YUV digitized format.

Claims7

Dependent claims

A method for controlling the color level in the color output of a video decoder, comprising the steps of:

deriving the color difference signals U and V in a YUV color format for a composite video signal;
providing an ideal burst amplitude of the composite video color signal;
measuring the actual burst amplitude of the composite video color signal;
determining as a scale factor the ratio of the measured burst amplitude to the ideal burst amplitude of the composite video color signal with a recursive relationship requiring only addition and subtraction;
determining a first and a second nominal correction factor for the U and V color difference signals, respectively, that represent a correction factor therefor,
scaling the first and second nominal correction factors with the determined scale factor with a recursive relationship that represents the respective first and second nominal correction factors divided by the determined scale factor, which recursive relationship utilizes only addition and subtraction to provide on the output thereof respective scaled first and second correction factors, and
scaling the color difference signals with the respective first and second scaled correction factors to provide scaled color difference signals U and V.

4 more elements

Dependencies are inferred from the claim text.