Differential pulse-coded modulation (DPCM) encoding of Gaussian autoregress
ive (AR) sequences is considered. It is pointed out that DPCM is rate-disto
rtion inefficient at low bit rates. Simple filtering modifications are prop
osed and incorporated into DPCM, A rate-distortion optimization framework t
hat results in optimal filters is presented. It is shown that the designed
filters take advantage of "less significant" process spectral components in
order to achieve superior rate-distortion performance, Design equations ar
e derived, issues related to optimization and complexity addressed. It is s
hown that simple DPCM systems with the proposed modifications significantly
outperform their standard counterparts.