Tuned degree-k zerotree wavelet coding with virtual nodes

A degree-k zerotree coder codes the significance of a spatial orientation tree (SOT) up to k levels. A SOT is referred to as a degree-k zerotree if all the nodes are insignificant with respect to a threshold except for the nodes in the top k levels. Coding with a higher degree zerotree requires fewer encoding bits especially at lower bit-rates where most of the coefficients are insignificant. However, it may be less efficient at higher bit-rates since the wavelet coefficients are more likely to be significant as the number of planes encoded is increased. In this paper, a tuned degree-k zerotree wavelet (TDKZW) coding scheme where the degree of zerotree tested is tuned at each coding pass is presented. The concept of virtual coding is also applied in conjunction with the proposed algorithm. Simulation results show that our proposed coding scheme consistently outperforms the traditional SPIHT binary encoded coding.