CODING OF SIGN INFORMATION IN DPCM SYSTEMS

摘要

A differential pulse code modulation system substantially reduces sign redundancy by transmitting sign information only for actual changes in polarity between differential samples. Upon the occurrence of a change in sign when both differential samples of opposite sign do not exceed a predetermined level, one of two polarity words is transmitted in place of the code word that represents the differential sample with the smaller magnitude. One polarity word indicates a positive polarity while the other word indicates a negative polarity. Only the absolute magnitudes of the differential samples are transmitted between sign changes. When both differential samples of opposite sign exceed a predetermined level, the absolute magnitude is transmitted for both differential samples and a run-length code work indicative of the location of the change in sign together with a polarity word are transmitted at a later time.