Source Coding for Multiple Descriptions

Let be a sequence of independent copies of the binary random variable X, where Pr{X = 0} = P r { Z = 1} = V2. Assume that this sequence appears at a rate of one symbol per second as the output of the data source in Fig. 1. The encoder in the figure observes this sequence and emits two binary sequences at rates R1, R2 1. These sequences are such that, by observing either one, a decoder can recover a good approximation to the source output, and by observing both sequences a decoder can obtain a better approximation to the source output. Letting D, D2, Do be the error rates which result when the streams at rate R1, rate R2, and both streams are used by a decoder, 1417 Fig. 1--Source encoder-decoder.