A Predictor Switching Scheme for DPCM Coding of Video Signals

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.