Low-rate tree coding of autoregressive sources (Corresp.)

The performance of differential pulse-code modulation and random codes is evaluated experimentally for a range of autoregressive sources, including Gaussian and Laplacian sources of orders1, 2, and3encoded at rates1, 2, and7. Correlations are typical of those encountered in speech and images. Results show that the gain from a fixed moderate degree of code searching increases as the rate decreases, and increases consistently with1 /D_{o}, whereD_{o}is the Berger-Gray critical distortion. Laplacian and Gaussian sources behave similarly. Random codes perform better than DPCM codes for lightly correlated Laplacian sources but are otherwise worse.