Convergence of distortion for block coding of symmetric modular sources (Corresp.)

We define a symmetric modular source to be a source-user pair consisting of an equiprobable discrete memoryless source together with a modular context-dependent fidelity criterion. For this source-user pair we establish the existence of block codes of fixed rate
R
greater than
R(D)
with average distortion that decreases towards
D
at a doubly exponential rate in block length.