Charles J Rubinstein

41258568, Nov 14, 1978

Aug 19, 1977

5/826057

Arun N. Netravali - Matawan NJ
Charles B. Rubinstein - Colts Neck NJ

Bell Telephone Laboratories, Incorporated - Murray Hill NJ

H04N 932

358 13

A system for encoding and decoding a color video signal wherein information obtained from the luminance component is used to reduce the amount of color information which must be sent from encoder to decoder. In the encoder, at least two different predictions are made of the present luminance sample, based upon individual or combined values of the previous luminance samples. Each prediction is evaluated against the true luminance value, to determine the best predictor pattern or strategy. If good correspondence exists between the true luminance value and the best prediction thereof, the same prediction strategy is used to predict the present color component value from previous color component values. The predicted color component (chrominance or chromaticity) value is not sent to the decoder, but is stored in the encoder; the decoder reconstructs the same predicted color component value by determining the best luminance predictor and then using that predictor on previous color component values, in a manner identical to that used in the encoder. If the correspondence between true and predicted luminance values is not good, it is assumed that the color component value is "unpredictable", so that the true color component value is then transmitted to the decoder.

40231992, May 10, 1977

Mar 9, 1976

5/665188

Arun Narayan Netravali - Matawan NJ
Charles Benjamin Rubinstein - Colts Neck NJ

Bell Telephone Laboratories, Incorporated - Murray Hill NJ

H04N 932

358 13

It has been determined that the amplitude accuracy required for specification of the chrominance portion of a color video signal is related to the spatial activity of the luminance portion of the signal. Accordingly, coding efficiency is improved in a digital transmission system by (1) defining a measure of the luminance activity and (2) changing chrominance coding strategy in accordance with the luminance activity measure. In one specific arrangement, coarse and fine quantizers are provided in an adaptive DPCM encoder. The coarse quantizer is used where luminance activity is high and the fine quantizer used only when the activity is low. In another arrangement, a variable gain circuit is disposed in the direct loop of an encoder with a fixed quantizer, and a variable attenuator is disposed in the feedback loop. For large spatial activity, the gain of the amplifier and the attenuator coefficient are held low; for small spatial activity the opposite condition prevails.

41410343, Feb 20, 1979

Aug 19, 1977

5/826025

Arun N. Netravali - Matawan NJ
Charles B. Rubinstein - Colts Neck NJ

Bell Telephone Laboratories, Incorporated - Murray Hill NJ

H04N 932
H04N 712
H04B 700

358 13

For a given transmission bit rate, the efficiency of encoding the color components of a color video signal is increased by utilizing information obtained from the luminance component to optimize color component encoding. Specifically, several predictions of the present luminance sample are formed using various individual values or combinations of previous luminance information. Each prediction is evaluated, and the best prediction technique is used to predict the present color sample, based upon previous color component information. Decoding in a remote receiver is accomplished similarly, by utilizing the luminance signal as a source for color component prediction information.