Discrete cosine transform-classified VQ technique for image coding

An image coding technique that combines the discrete cosine transform (DCT) and the classified vector quantizer (CVQ) is described. In this scheme, the DCT domain block is partitioned into vectors and then vector-quantized. The partition of the DCT block into vectors and the CVQ approach result in a much less complex coder than a conventional VQ in the spatial domain. A simple classification algorithm using two DCT coefficients and variance of the input DCT block as features for the classifier is proposed. Adaptive partitioning of the DCT block and bit assignment are found to be essential to achieve the overall goal. With the proposed DCT-CVQ visual quality comparable to that produced by existing coders is demonstrated for rates in the range of 0.45-0.65 bits/pixel