Abstract
Abstract Embedded ZeroBlock Coding and context modeling (EZBC) algorithm has high compression performance. However, it consumes large amounts of memory space because an Amplitude Quadtree of wavelet coefficients and other two link lists would be built during the encoding process. This is one of the big challenges for EZBC to be used in real time or hardware applications. An improved EZBC algorithm based on bit length of coefficients was brought forward in this article. It uses Bit Length Quadtree to complete the coding process and output the context for Arithmetic Coder. It can achieve the same compression performance as EZBC and save more than 75% memory space required in the encoding process. As Bit Length Quadtree can quickly locate the wavelet coefficients and judge their significance, the improved algorithm can dramatically accelerate the encoding speed. These improvements are also beneficial for hardware. PACS: 42.30.Va, 42.30.Wb
Highlights
At present, the typical embedded wavelet-based image coding methods includes Embedded Zerotree Wavelet coder (EZW) [1] proposed by Shapiro, Set Partitioned in Hierachical Tree (SPIHT) [2] proposed by Said etc., Set Partition Embedded block algorithm (SPECK) [3] proposed by Asad Islam, Embedded Block Coding with Optimal Truncation (EBCOT) [4] used in JPEG2000 [5], and Embedded ZeroBlock Coding and context modeling (EZBC) [6] proposed by Shih-Ta Hsiang etc.Among these algorithms, EZW and SPIHT were based on the local characteristic in spatial-frequency domain of wavelet transform
During the encoding process EZBC built an Amplitude Quadtree Qk[l](i, j) and two link lists: the insignificant nodes link list LIN and the significant pixels link list LSP. Both Amplitude Quadtree Qk[l](i, j) and the link lists consumed a large amounts of memory space and this was one of the big challenges for the EZBC to be used in real time or hardware applications
As Bit Length Quadtree can quickly locate the wavelet coefficients, judge their significance, and avoid a large amount operations of link lists used in EZBC, this algorithm can accelerate the encoding speed effectively
Summary
The typical embedded wavelet-based image coding methods includes Embedded Zerotree Wavelet coder (EZW) [1] proposed by Shapiro, Set Partitioned in Hierachical Tree (SPIHT) [2] proposed by Said etc., Set Partition Embedded block algorithm (SPECK) [3] proposed by Asad Islam, Embedded Block Coding with Optimal Truncation (EBCOT) [4] used in JPEG2000 [5], and Embedded ZeroBlock Coding and context modeling (EZBC) [6] proposed by Shih-Ta Hsiang etc.Among these algorithms, EZW and SPIHT were based on the local characteristic in spatial-frequency domain of wavelet transform. It used Bit Length Quadtree instead of Amplitude Quadtree of wavelet coefficients and other two link lists, so it can save more than 75% memory space required in the encoding process. As Bit Length Quadtree can quickly locate the wavelet coefficients, judge their significance, and avoid a large amount operations of link lists used in EZBC, this algorithm can accelerate the encoding speed effectively.
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