Overlap in Adaptive Vector Quantization
DCC '01 Proceedings of the Data Compression Conference
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In this poster we present a new AVQ-based video coder for very low bitrates. To encode a block from a frame, the encoder offers three modes: 1. A block from the same position in the last frame can be taken, 2. the block can be represented with a vector from the codebook or 3. a new vector, that sufficiently represents a block, can be inserted into the codebook. For mode 2 a mean-removed VQ scheme is used. The decision how blocks are encoded and how the codebook is updated is done in an R-D optimized fashion. The codebook of shape blocks is updated once per frame. First results for an implementation of such a scheme have been reported in our previous paper [2]. Here we extend the method to incorporate a wavelet image transform before coding in order to enhance the compression performance. In addition the rate-distortion optimization is comprehensively discussed. Our R-D optimization is based on an efficient convex-hull computation [3]. This method is compared to common R-D optimizations that use a Lagrangian multiplier approach.