Performance improvement of the SPIHT coder

The set partitioning in hierarchical trees (SPIHT) coder is one of the state-of-the-art coders among the wavelet-based image compression coders. For improving the performance of the SPIHT coder, in this paper, we propose a pre-processing method that applies the discrete sine transform or the discrete cosine transform to the wavelet coefficients in the highest frequency subbands and in the next highest frequency subbands before the SPIHT encoding. Experimental results show that the proposed method increases the peak signal to noise ratio by up to 0.4 (dB) in textured images over the original SPIHT coder.