Quadtree based classification with arithmetic and trellis coded quantization for subband image coding

In this a paper a quadtree based method is proposed for classifying blocks of samples in image subbands. 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, so do the overheads for transmitting the classification information. The quadtree based method proposed in this paper 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. Using an efficient quantization scheme such as ACTCQ (arithmetic and trellis coded quantization), we have been able to demonstrate competitive coding results at low bit-rates.