In DPCM coding of video signals, for improved data compression efficiency, the predictor is often switched adaptively between two or more different predictions. For low-bit-rate coders, the predictor switching is done on a pel-by-pel basis. In this paper, a new scheme for predictor switching on a pel-by-pel basis is proposed. This new scheme is a modification of an existing adaptive predictor switching scheme which has been implemented in pel-recursive motion compensated coding of video signals. To evaluate the efficiency of the new scheme, a theoretical expression for the output bit rate is derived. It is pointed out under what conditions it is advantageous to use the new scheme for predictor switching. Some details of implementation are discussed. Results of computer simulation on natural scenes are presented. These results validate the theoretical conclusions derived in the paper. The simulation results also indicate that the picture quality is improved significantly, for approximately the same output bit rate, with the new predictor switching scheme as compared to the existing scheme for predictor switching.

This paper is concerned with motion compensation techniques for predictive coding of the composite (frequency multiplexed) color television signal. Motion estimation algorithms developed in this paper are recursive and are extensions of our previous algorithms developed for baseband luminance signals. We show, by computer simulations, that displacement of objects from frame to frame can be estimated in the composite signal domain without decomposing the composite signal into its original components. However, due to the poorer quality of displacement estimation and the resulting prediction, motion compensation in the composite signal domain is not as efficient as motion compensation in the component domain. Simulations indicate that a motion compensated predictive coder requires, in some cases, up to 25 percent fewer bits than a coder that uses previous field prediction.

We develop and evaluate motion compensation schemes for predictive coding of the component color television signal. Algorithms are discussed for estimation of motion of each color component (luminance and chrominance) separately as well as in combination. Techniques for switching of the predictors for individual components are proposed and simulated. Simulations show that it is sufficient to estimate parameters of motion based only on the luminance and use them for motion-based prediction and switching the predictors for both the luminance and chrominance. Thus, only one motion estimator and prediction switch is needed for the three components of the color signal. Compression capability of motion compensation is scene dependent, in some video conference type of scenes, bit rate is reduced by as much as 60 percent compared to conditional replenishment coding.