Iterative Joint Video and Channel Decoding in a Trellis-Based Vector-Quantized Video Codec and Trellis-Coded Modulation Aided Wireless Videophone

Abstract

We propose a Vector-Quantized (VQ) video codec that induces deliberately-introduced code constraints. The complete set of these code constraints are unambiguously described by a novel block-based modification of a symbol-based variable length coding trellis structure. This trellis is employed during VQ encoding to represent video information with a Minimum Mean Squared Error (MMSE) reconstruction. Additionally, the proposed trellis structure is employed in the video decoder to obtain a posteriori probability based MMSE estimates of the transmitted VQ tiles. Since the trellis structure unambiguously describes the code constraints induced by the video codec, its employment guarantees the automatic recovery of valid sets of VQ tiles. The proposed video codec is serially concatenated with a trellis-coded modulation scheme for transmission over a fast-fading Rayleigh fading channel. In the receiver, iterative-decoding convergence that eliminates all perceivable channel-induced video distortion is shown to be supported within 1.29 dB of the system's 2 bit/s/Hz channel-capacity limit of 3.96 dB