Modified EZW and SPIHT algorithms for perceptually audio and high quality speech coding

This paper evaluates the problems of implementing two well-known zero-tree-based re-encoding schemes of Embedded Zero-tree Wavelet (EZW) and the set partitioning in hierarchical trees (SPIHT) for perceptually audio and high quality speech coding. Since the original EZW and SPIHT algorithms are designed for image compression, some new modifications have been implemented in these schemes for their better matching with audio signals. The performances of these two re-encoders are compared in terms of average output bit rate and computation time of a same codec. It is concluded that the proposed modifications can improve the performance of both algorithms by about 20-30%. Furthermore, it is shown that the modified EZW algorithm achieves relatively better average bit rates although it has lower speed in comparison to the modified SPIHT algorithm.