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Friday, November 30, 9:00 - 11:30 am

W1: Digital Audio Signal Processing - The Good, the Bad, and the Ugly

Stanley P. Lipshitz, University of Waterloo, Waterloo, Ontario, Canada

Robert Adams, Analog Devices, Acton, MA, USA
Stanley P. Lipshitz
Derk Reefman, Philips Research Laboratories, Eindhoven, The Netherlands

High-quality digital audio signal processing is not as straight-forward as it appears at first sight. As we move into the era of high-resolution digital audio, the quality of the associated signal processing must increase commensurately. Almost every digital operation has an associated penalty in terms of noise and distortion. Traps abound, and some of the more esoteric types of processing errors may not be revealed without careful listening tests or special test signals. Experts in digital audio signal processing will address signal processing areas that are subject to these pitfalls and will explain both the problems and solutions. Although this workshop will assume that the audience has some familiarity with digital signal processing theory and practice, the presentations will be such that even those without much background will also benefit by attending.

"Introductory Survey of Quantization, Dither, and Noise Shaping,"
by Stanley P. Lipshitz
Good digital signal processing is just as difficult as good analog signal processing! Almost any operation on digital data results in correlated round off errors, and they can be pernicious if not treated properly. This talk will review the nature of these quantization errors, show how they can be made innocuous by proper dithering, and discuss the need for dither in noise shapers and sigma-delta modulators. Examples will be played to illustrate these features.

"Under the Hood of Modern A/D and D/A Converters,"
by Robert Adams
Audio analog-to-digital and digital-to-analog converters have progressed from R-2R ladders to 1-bit sigma-delta converters to multibit noise-shaping converters with advanced mismatch-shaping schemes. This talk will discuss the pros and cons of various converter architectures, with particular attention paid to the limitations of 1-bit converters and how they impact the design of SACD encoders and decoders. An overview of the signal processing found in a modern converter IC will be given, and the tradeoffs of various DSP architectures will be discussed.

"The Right and the Wrong Way of Processing 1-Bit Signals,"
by Derk Reefman
An overview will be given of the various ways to process DSD signals. Attentions will be paid to some of the pitfalls and the way to either avoid them or cover them up. Also some interesting different possibilities for the creation of bitstreams will be addressed.

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