Parametric Coding of Stereo Audio
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Parametric Coding of Stereo Audio Jeroen Breebaart Digital Signal Processing Group, Philips Research Laboratories, 5656 AA Eindhoven, The Netherlands Email: [email protected]
Steven van de Par Digital Signal Processing Group, Philips Research Laboratories, 5656 AA Eindhoven, The Netherlands Email: [email protected]
Armin Kohlrausch Digital Signal Processing Group, Philips Research Laboratories, 5656 Eindhoven, The Netherlands Department of Technology Management, Eindhoven University of Technology, 5656 AA Eindhoven, The Netherlands Email: [email protected]
Erik Schuijers Philips Digital Systems Laboratories, 5616 LW Eindhoven, The Netherlands Email: [email protected] Received 27 January 2004; Revised 22 July 2004 Parametric-stereo coding is a technique to efficiently code a stereo audio signal as a monaural signal plus a small amount of parametric overhead to describe the stereo image. The stereo properties are analyzed, encoded, and reinstated in a decoder according to spatial psychoacoustical principles. The monaural signal can be encoded using any (conventional) audio coder. Experiments show that the parameterized description of spatial properties enables a highly efficient, high-quality stereo audio representation. Keywords and phrases: parametric stereo, audio coding, perceptual audio coding, stereo coding.
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INTRODUCTION
Efficient coding of wideband audio has gained large interest during the last decades. With the increasing popularity of mobile applications, Internet, and wireless communication protocols, the demand for more efficient coding systems is still sustaining. A large variety of different coding strategies and algorithms has been proposed and several of them have been incorporated in international standards [1, 2]. These coding strategies reduce the required bit rate by exploiting two main principles for bit-rate reduction. The first principle is the fact that signals may exhibit redundant information. A signal may be partly predictable from its past, or the signal can be described more efficiently using a suitable set of signal functions. For example, a single sinusoid can be described by its successive time-domain samples, but a more efficient description would be to transmit its amplitude, frequency, and 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.
starting phase. This source of bit-rate reduction is often referred to as “signal redundancy.” The second principle (or source) for bit-rate reduction is the exploitation of “perceptual irrelevancy.” Signal properties that are irrelevant from a perceptual point of view can be discarded without a loss in perceptual quality. In particular, a significant amount of bit-rate reduction in current state-of-the-art audio coders is obtained by exploiting auditory masking. Basically, two different coding approaches can be distinguished that aim at bit-rate red
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