MULTIPLE DESCRIPTION SOURCE-CODING WITH NO EXCESS MARGINAL RATE

Multiple description source coding concerns situations in which the transmission of the source information is distributed over two data streams at rates R(1) and R(2), respectively. When both data streams are received, the decoder uses the combined data at rate R(1) + R(2) to reconstruct the source information with average distortion d(0). If a communication breakdown prevents one of the data streams from reaching the receiver, the decoder has to base its reconstruction solely on the available data at rate either R(1) or R(2). This results in a higher distortion of either d(1) or d(2), respectively. The region R of all achievable quintuples (R(1), R(2), d(0), d(1), d(2)) has been determined in the so-called ''no excess rate'' sum case defined by imposing the requirement R(1) + R(2) = R(d(0)), where R(.) is the rate-distortion function of the source. The case with excess rate sum, characterized by R(1) + R(2) > R(d(0)), is challenging. We study in this paper a special case of it in which the requirements R(t) = R(d(t)), t = 1, 2, are imposed; we refer to this as the ''no excess marginal rate'' case. The lower and upper bounds on d(0) we obtain are separated by only a tiny gap when evaluated for a binary equiprobable source and the Hamming distortion measure.