Adaptive vector quantization of image sequences using generalized threshold replenishment

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. Rate-distortion cost criteria are used in the determination of nearest-neighbor codewords and as well as in the decision to update the codebook. Results presented indicate that, for the coding of an image sequence: (1) most AVQ algorithms achieve distortion much lower than that of nonadaptive VQ for the same rate (about 1.5 bits/pixel), and (2) the GTR algorithm achieves rate-distortion performance substantially superior to that of other AVQ algorithms for low-rate coding, being the only algorithm to achieve a rate below 1.0 bits/pixel