Several Kinds of Modified SPIHT Codec

SPIHT (Set Partitioning In hierachical trees), being an efficient coding method for wavelet coefficients, has acquired more and more widely application, especially in image/video compression fields. But, conventional SPHIT have some obvious limitions. For example, when for the color image compression, polarmetric SAR image compression, or multispectrum image compression and other multi-channel image compression, there are only very limited image planes(R,G,B for color image, HH, HV,VVfor polarmetric SAR images) but there exist large amount of information redundancy among the image planes. So, considering the support length of discrete wavelet transform, we can’t use the set 8-partition methods such as 3D-SPIHT which has been used for video compression. Another example, when the input image is unsymmetrical such as 16x512 image block even only one line image content, which is very common in hardware design, because it means the larger final chip die size for the many line buffers. But, the traditional SPIHT codec can acquire the best compression performances only for the image is symmetrical in horizontal and vertical dimension. To the above specific applications, I will discuss several kinds of modified SPIHT in this chapter, most of them are the author’s newly research result. In the following section, We will give a simple description about the traditional SPIHT codec, then, we will take the polarimetric SAR intensity image compression as example and give some specific compression method for multi-channel image compression. Certainly, before encoding for the wavelet coefficients, we need a 3D matrix transform to remove the information redundancy among the image plane and in each image plane. For the unsymmetrical image compression used in hardware design, an unsymmetrical SPIHT codec is detailed addressed, at the time, its specific case for only 1 line image compression, 1D SPIHT codec is also given.