Quadtree-based classification in subband image coding

Classification of blocks of subband samples according to their energy and variable bit allocation within the subsequent classes has demonstrated considerable gains in coding efficiency. The gains due to classification increase as smaller blocks are used; however, this increases the overheads for transmitting the classification information. In this paper, a quadtree based method is proposed. This method allows for more efficient classification by using variable-sized blocks in order to maximize the classification gain, while maintaining a limit on the classification overheads. This method is applied for subband coding of images and the results indicate that it performs better than the other methods currently available in the literature. (C) 2003 Elsevier Inc. All rights reserved.