Iterative Wyner-Ziv decoding and successive side-information refinement in feedback channel-free hash-based distributed video coding

This work presents a novel rate control scheme that suppresses the need for a feedback channel in hash-based distributed video coding (DVC) architectures. Our state-of-the-art DVC schemes generate side-information (SI) at the decoder by means of hash-based overlapped block motion estimation followed by probabilistic motion compensation, where key frames or previously decoded non-key frames, called Wyner-Ziv frames, are used as references. These DVC systems employ powerful low-density parity-check accumulate codes to code the Wyner-Ziv frames in the transform domain. Our previous DVC architectures use a classical decoder-driven rate control scheme with a feedback channel. Specifically, chunks of accumulated syndrome bits are sent from the encoder to the decoder upon request from the latter until successful decoding is achieved. In order to suppress the feedback channel, the encoder of the DVC system, proposed in this work, approximates the SI available to the decoder using a novel low complexity SI generation technique. Subsequently, the conditional probabilities of the original Wyner-Ziv frames, given the approximation of the SI at the encoder, are used to generate an estimate of the required rate for channel decoding. Hence the presence of a feedback channel is evaded. Additionally, the proposed feedback channel-free DVC system is equipped with advanced reconstruction techniques to reduce the impact of failed channel decoding. In this context, our DVC architecture features iterative refinement of the SI at the decoder. The latter allows for reattempting to decode Wyner-Ziv data for which the channel decoding failed in previous decoding steps when only a lower quality version of the SI was available. Experimental results show competitive compression performance of our novel feedback channel-free hash-based DVC system with respect to the feedback channel-based benchmark in DVC.