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Generalized threshold replenishment: An adaptive vector quantization algorithm for the coding of nonstationary sources

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IEEE TRANSACTIONS ON image PROCESSING 1998年第10期7卷 1410-1424页

作者： Fowler, JE Ohio State Univ Dept Elect Engn Columbus OH 43210 USA

In this paper, we describe a new adaptive-vector-quantization (AVQ) algorithm designed for the coding of nonstationary sources. This new algorithm, generalized threshold replenishment (GTR), differs from prior AVQ algorithms in that it features an explicit, online consideration of both rate and distortion. Because of its online nature, GTR is more amenable to real-time hardware and software implementation than are many prior AVQ algorithms that rely on traditional batch training methods. Additionally, as rate-distortion cost criteria are used in bath the determination of nearest-neighbor codewords and the decision to update the codebook, GTR achieves rate-distortion performance superior to that of other AVQ algorithms, particularly for low-rate coding. Results are presented that illustrate low-rate performance surpassing that of other AVQ algorithms for the coding of both an image sequence and an artificial nonstationary random process. For the image sequence, it is shown that 1) most AVQ algorithms achieve distortion much lower than that of nonadaptive VQ for the same rate (about 1.5 b/pixel), and 2) GTR achieves performance substantially superior to that of the other AVQ algorithms for low-rate coding, being the only algorithm to achieve a rate below 1.0 b/pixel.

关键词： adaptive vector quantization generalized threshold replenishment image-sequence coding

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Adaptive vector quantization for efficient zerotree-based coding of video with nonstationary statistics

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 2000年第8期10卷 1478-1488页

作者： Fowler, JE Univ Nice Lab I3S Sophia Antipolis France

A new system for intraframe coding of video is described. This system combines zerotrees of vectors of wavelet coefficients and the generalized-threshold-replenishment (GTR) technique for adaptive vector quantization (AVQ). A data structure, the vector zerotree (VZT), is introduced to identify trees of insignificant vectors, i.e., those vectors of wavelet coefficients in a dyadic subband decomposition that are to be coded as zero. GTR coders are then applied to each subband to efficiently code the significant vectors by way of adapting to their changing statistics. Both VZT generation and GTR coding are based upon minimization of criteria involving both rate and distortion. In addition, perceptual performance is improved by invoking simple, perceptually motivated weighting in both the VZT and the GTR coders. Our experimental findings indicate that the described VZT-GTR system handles dramatic changes in image statistics, such as those due to a scene change, more efficiently than wavelet-based techniques employing nonadaptive scalar quantizers.

关键词： adaptive vector quantization image-sequence coding zerotree coding

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