A review of algorithms for perceptual coding of digital audio signals

During the last decade, CD-quality digital audio has essentially replaced analog audio. During this sn,ne period new digital audio applications have emerged for network, wireless, and multimedia computing systems, which face such constraints as reduced channel bandwidth, limited storage capacity, and low cost. These new applications have created a demand for high-quality digital audio delivery at low bit rates. In response to this need, consider-able research has been devoted to the development of algorithms for perceptually transparent coding of high-fidelity (CD-quality) digital audio. As a result many algorithms have been proposed, and several have now become international and/or commercial product standards. This paper reviews algorithms for perceptually transparent coding of CD-quality digital audio, including both research and standardization activities. The paper-is organized as follows. First, psychoacoustic principles are described with the MPEG psychoacoustic signal analysis model I discussed in some detail. Then, we review methodologies which achieve perceptually transparent coding of FM-and CD-quality audio signals, including algorithms which manipulate transform components and subband signal decompositions. The discussion concentrates on architectures and applications of those techniques which utilize psychoacoustic models to exploit efficiently masking characteristics of the human receiver. Several algorithms which have become commercial and/or commercial standards are also presented including the ISO/MPEG family and the Dolby AC-3 algorithms. The pal,er concludes with a brief discussion of future research directions.