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Flexible Zerotree Coding of Wavelet Coefficients
Sanghyun JOO Hisakazu KIKUCHI Shigenobu SASAKI Jaeho SHIN
Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Vol.E82A
No.6
pp.11171125 Publication Date: 1999/06/25 Online ISSN:
DOI: Print ISSN: 09168508 Type of Manuscript: PAPER Category: Image Theory Keyword: image compression, wavelet transform, zerotree coding,
Full Text: PDF(1.6MB)>>
Summary:
We introduce an extended EZW coder that uses flexible zerotree coding of wavelet coefficients. A flexible parentchild relationship is defined so as to exploit spatial dependencies within a subband as well as hierarchical dependencies among multiscale subbands. The new relationship is based on a particular statistics that a large coefficient is more likely to have large coefficients in its neighborhood in terms of space and scale. In the flexible relationship, a parent coefficient in a subband relates to four child coefficients in the next finer subband in the same orientation. If each of the children is larger than a given threshold, the parent extends its parentship to the neighbors close to its conventional children. A probing bit is introduced to indicate whether a significant parent has significant children to be scanned. This enables us to avoid excessive scan of insignificant coefficients. Also, produced symbols are resymbolized into simple variablelength binary codes to remove some redundancy according to a predefined rule. As a result, the wavelet coefficients can be described with a small number of binary symbols. This binary symbol stream gives a competitive performance without an additional entropy coding and thus a fast encoding/decoding is possible. Moreover, the binary symbols can be more compressed by an adaptive arithmetic coding. Our experimental results are given in both binarycoded mode and arithmeticcoded mode. Also, these results are compared with those of the EZW coder.

