| 摘要 |
A differential pulse code modulation (DPCM) coder with a predictor chain (24) has its coefficients 26 determined 39 from the coefficients of an adaptive least mean squares (LMS) predictor with a predictor chain 30 whch may be same as the DPCM predictor chain. In order to improve DPCM coding efficiency while retaining adequate error performance the picture being processed may be divided into a plurality of blocks. The DPCM coefficients for each block are determined separately by respective LMS predictors. Alternatively or additionally, stability is enhanced by one or more of the following: LMS coefficient increments are reduced in magnitude by a fraction of the sum of all these increments. The LMS predictor is moderated by adding a small fraction of a stable predictor. A stability condition is imposed on the LMS predictor or on the DPCM coder. A quantizer is introduced to add pseudo-random noise. The DPCM coefficients are changed less frequently than the LMS coefficients, e.g. on the basis of average of the latter. <IMAGE> |
