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A Robust Reversed-Complexity Wyner-Ziv Video Codec Introducing Sign-Modulated Codes
Keyword(s): Wyner-Ziv coding; distributed coding; Viterbi algorithm; forward-backward algorithm; noisy channel
Abstract: A framework for incorporation of a Wyner-Ziv frame coding mode in existing video codecs is presented, to enable a mode of operation with low encoding complexity. The core Wyner-Ziv frame coder works on the Laplacian residual of a lower-resolution frame encoded by a regular codec at reduced resolution. The quantized transform coefficients of the residual frame are mapped to odd cosets to enable reuse of the same entropy coder that already exists in a regular codec without loss in efficiency. The decoder iteratively conducts motion-based side-information generation and coset decoding, to gradually refine the estimate of the frame. In addition, a technique called Trellis Coded Sign Modulation (TCSM) using tail-biting trellises based on modulating the signs of the coset indices is proposed, in order to reduce errors while preserving the entropy of the coset indices transmitted. Preliminary results are presented for application to the H.263+ video codec. These codes easily extend to sign-modulated Turbo codes, and sign-modulated block codes, including LDPC codes.
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