Perceptually Motivated Sub-band Decomposition for FDLP Audio Coding

• Published in: Text, Speech and Dialogue pp. 435 - 442
• Main Authors: Motlíček, Petr, Ganapathy, Sriram, Hermansky, Hynek, Garudadri, Harinath, Athineos, Marios
• Format: Book Chapter
• Language: English
• Published: Berlin, Heidelberg Springer Berlin Heidelberg
• Series: Lecture Notes in Computer Science
• Subjects: Advance Audio Code; Audio Code; Audio Quality; Audio Sample; Quadrature Mirror Filter
• ISBN: 9783540873907; 3540873902
• ISSN: 0302-9743; 1611-3349
• DOI: 10.1007/978-3-540-87391-4_56

This paper describes employment of non-uniform QMF decomposition to increase the efficiency of a generic wide-band audio coding system based on Frequency Domain Linear Prediction (FDLP). The base line FDLP codec, operating at high bit-rates (~136 kbps), exploits a uniform QMF decomposition into 64 sub-bands followed by sub-band processing based on FDLP. Here, we propose a non-uniform QMF decomposition into 32 frequency sub-bands obtained by merging 64 uniform QMF bands. The merging operation is performed in such a way that bandwidths of the resulting critically sampled sub-bands emulate the characteristics of the critical band filters in the human auditory system. Such frequency decomposition, when employed in the FDLP audio codec, results in a bit-rate reduction of 40% over the base line. We also describe the complete audio codec, which provides high-fidelity audio compression at ~66 kbps. In subjective listening tests, the FDLP codec outperforms MPEG-1 Layer 3 (MP3) and achieves similar qualities as MPEG-4 HE-AAC codec.