VLSI design af a DWT/modified efficient SPIHT based image codec

Set partitioning in hierarchical trees (SPIHT) is a highly efficient technique for compressing discrete wavelet transform (DWT) decomposed images. Though its compression efficiency is a little less than famous embedded block coding with optimized truncation (EBCOT) adopted by JPEG2000, a codec standard for still images, SPIHT has a straightforward coding procedure and requires no tables. These make SPIHT a more appropriate algorithm for hardware implementation. In this paper, a modified SPIHT algorithm is presented. The modifications include a simplification of coefficient scanning process, a 1-D addressing method instead of the original 2-D arrangement for wavelet coefficients and a fixed memory allocation for the data lists instead of a dynamic allocation required in the original SPIHT. Though distortion is slightly increased, it enjoys an extremely fast throughput and easier hardware implementation. The gate counts of a 16-by-16 DWT/IDWT and a modified SPIHT/inv-SPIHT are 12,458 and 5,758 respectively. A complete image codec is also provided.