Mini-max algorithm for image adaptive vector quantisation

Vector quantisation is a promising method for low bit rate image compression. In vector quantisation, the image vectors are usually coded using a ´universal codebook´ generated from a set of training images. The coding performance is potentially poor for images outside the training set. A number of inter- and intra-image techniques have been proposed to adapt the codewords to the input image. The authors propose an intra-image adaptive technique which employs a criterion that minimises the maximum error. Here, the codebook is generated on the fly from the input vectors to be coded. A primary codebook of size two, four or eight is typically used to store the frequently used codewords. A larger secondary codebook is used to store the less frequently used codewords.<>