Result: High-rate quantization and transform coding with side information at the decoder : Distributed source coding

We extend high-rate quantization theory to Wyner-Ziv coding, i.e., lossy source coding with side information at the decoder. Ideal Slepian-Wolf coders are assumed, thus rates are conditional entropies of quantization indices given the side information. This theory is applied to the analysis of orthonormal block transforms for Wyner-Ziv coding. A formula for the optimal rate allocation and an approximation to the optimal transform are derived. The case of noisy high-rate quantization and transform coding is included in our study, in which a noisy observation of source data is available at the encoder, but we are interested in estimating the unseen data at the decoder, with the help of side information. We implement a transform-domain Wyner-Ziv video coder that encodes frames independently but decodes them conditionally. Experimental results show that using the discrete cosine transform results in a rate-distortion improvement with respect to the pixel-domain coder. Transform coders of noisy images for different communication constraints are compared. Experimental results show that the noisy Wyner-Ziv transform coder achieves a performance close to the case in which the side information is also available at the encoder.