ABSTRACT
This chapter uses two-channel stereo signals as a baseline, but 5.1 channels are ubiquitous and immersive formats are envisioned in next-generation audio systems. It presents the technical details of several audio compression systems that are widely adopted in the marketplace, or are anticipated to have a significant impact on the marketplace. Continuing advances in digital signal processing technology make it possible to create low-cost, real-time hardware for digital audio signal compression that implement complex and powerful signal processing algorithms. The most important contribution to compression in perceptual coders comes from irrelevancy reduction. Hence, lossless compression systems remove only the redundancy in a signal, while lossy compression systems remove both redundancy and irrelevancy. The human auditory system itself can be modeled as a subband filter bank, but one with nonuniform bandwidths that are narrow at low frequency and wide at high frequency.
