Table of Contents
ISRN Signal Processing
Volume 2011 (2011), Article ID 145758, 16 pages
Research Article

Adaptive Variable Degree- π‘˜ Zero-Trees for Re-Encoding of Perceptually Quantized Wavelet Packet Transformed Audio and High-Quality Speech

1Department of Electrical and Computer Engineering, Shahid Beheshti University, Evin Sq., Tehran 1983963113, Iran
2Audio and Speech Processing Group, Research Center of Intelligent Signal Processing (RCISP), Tehran 1661617733, Iran

Received 13 November 2010; Accepted 23 December 2010

Academic Editors: Y. H. Chan and B. N. Chatterji

Copyright © 2011 Omid Ghahabi and Mohammad Hassan Savoji. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


A fast, efficient, and scalable algorithm is proposed, in this paper, for re-encoding of perceptually quantized wavelet-packet transform (WPT) coefficients of audio and high quality speech and is called “adaptive variable degree- π‘˜ zero-trees” (AVDZ). The quantization process is carried out by taking into account some basic perceptual considerations and achieves good subjective quality with low complexity. The performance of the proposed AVDZ algorithm is compared with two other zero-tree-based schemes comprising (1) embedded zero-tree wavelet (EZW) and (2) the set partitioning in hierarchical trees (SPIHT). Since EZW and SPIHT are designed for image compression, some modifications are incorporated in these schemes for their better matching to audio signals. It is shown that the proposed modifications can improve their performance by about 15–25%. Furthermore, it is concluded that the proposed AVDZ algorithm outperforms these modified versions in terms of both output average bit-rates and computation times.