中文摘要：

在3D-SPIHT编码的基础上,提出基于不对称小波树的分方向4D-SPIHT编码算法,通过构造4维不对称小波树结构,使得每一维上的小波分解级数可以灵活选择;根据小波树特点,将各小波频带按方向独立进行SPIHT编码,从而加快编码速度。实验结果表明,该算法能较有效地去除三维体数据之间的相关性,在不明显增加算法复杂度的基础上,提高压缩性能和编码效率。

英文摘要：

The improved 4D-SPIHT algorithm based on the asymmetric wavelet tree is proposed.In the scheme,a 4D asymmetric wavelet tree is used,in which way different numbers of wavelet decompositions in each dimension can be chosed.Then the paper uses SPIHT to code wavelet coefficients band by band,which speeds up the encoding speed.Experiments show that the algorithm can remove the relevant in the 3D volume data,and increase the compression performance and coding efficiency with no significant complexity of the algorithm increased.