Noiseless coding of correlated information sources

A new class of lower bounds to rate-distortion functions ofstationary processes with memory and single-letter vector-valued distor-tion measures is derived. This class is shown to include or imply all otherwell-known lower bounds to rates of such sources and distortion measures.The derivation is based on the definition and properties of the conditionalratedistortion function. In addition to providing a unified and intuitive Manuscript received May 2, 1972; revised September 6, 1972. Thiswork was supported in part by the National ScienceFoundation underGrants GK-5452 and GK-31630 and by the Joint Service Program atStanford Electronics Laboratory under U.S. Navy Contract N00014-67-A-0112-004.The author is with the Department of Electrical Engineering,Stanford University, Stanford, Calif. 94305.approach to lower bounds, this approach yields several interesting rela-tions among conditional, joint, and marginal rates that are similar toand sometimes identical with the analogous relations among the corre-sponding entropies.