Rate-distortion theory for context-dependent fidelity criteria

A lower bound is obtained to the rate-distortion function of a finite-alphabet stationary source with respect to a context-dependent fidelity criterion. For equiprobable memoryless sources and modular distortion measures, for all . It is conjectured that, for a broad class of finite-alphabet sources and context-dependent fidelity criteria, there exists a critical distortion such that for . The case of a binary source and span-2 distortion measure is treated in detail. Among other results a coding theorem is proved that establishes that , where is the golden ratio, .