Improving the rate-distortion performance of DPCM

Differential pulse coded modulation (DPCM) is able to code highly correlated sources efficiently at high bit rates but not at low bit rate regions. Motivated by the rate distortion theory, a simple modified DPCM codec using multirate processing is proposed. A low-pass filter is used to limit the source signal spectrum. Further bit rate reduction is achieved by reducing the number of transmitted samples through down-sampling. A Wiener filter is appended at the decoder for further noise reduction. Simulation results show that for a 1 st order autoregressive (AR(1)) process, the proposed codec makes substantial improvements over the classic DPCM and performs close to the rate-distortion bound.