Sunday, May 29, 2005 – 18:15-20:00
The Rise of Digital Audio: The Good, the Bad, and the Ugly
by Prof. Stanley P. Lipshitz
The Richard C. Heyser distinguished lecturer for the 118th AES Convention is Stanley P. Lipshitz. He is a professor in the departments of Applied Mathematics and of Physics at the University of Waterloo in Waterloo, Ontario, Canada. He is one of the founding members of the Audio Research Group, which conducts research in many areas of audio and electroacoustics. Lipshitz is a fellow of the Audio Engineering Society, a recipient of its Silver Medal for his research contributions to digital audio and of its Publication Award (jointly with John Vanderkooy and Robert Wannamaker) for a survey paper on quantization and dither in the Journal of the Audio Engineering Society. He has served as a governor of this Society and was its president in 1988-1989. Other society memberships include the IEEE, the Acoustical Society of America, and the Canadian Acoustical Association. He has presented numerous technical papers, on a wide range of topics, at conferences both in North America and overseas. As vice president of the Kitchener-Waterloo Chamber Music Society, he records and broadcasts about 50 local classical music concerts annually and has been doing so digitally for more than 20 years. Lipshitz’s lecture is entitled “The Rise of Digital Audio: The Good, the Bad, and the Ugly.”
Like any new technology, digital audio suffered some growing pains during its early years. Some of the early criticisms were the result of digital artifacts caused by imperfectly-working hardware, which needs a precision that was not, at the time, easily achieved and maintained in the field. Some were a consequence of badly-chosen software algorithms in the early digital editing systems. Some critics believed that digital audio systems were inherently flawed and less accurate than the best analog recording systems. Most audio engineers, on the other hand, believed that any audible deficiencies were not intrinsic, but were hardware- and software-related, and thus amenable to elimination by proper design and construction.
In this lecture I will reminisce about some of these early growing pains and discuss the “deficiencies,” both real and imagined. I shall use musical examples taken from early CD releases to illustrate many of the real problems. Additional musical examples will illustrate their solutions, most of which follow from an understanding of the sampling and quantizing theorems, and what they tell us about representing and processing musical signals numerically. They have largely been implemented. Some imaginary deficiencies were thought to be the result of:
* The discontinuous nature of digital data compared with continuous (analog) musical data,
* A sampling rate that is inadequate to capture the subtler nuances of the music, and
* A word-length that is inadequate to resolve the smallest details of the sound.
Imaginary problems, of course, don’t have real solutions! Why were these problems imaginary?
So, what is digital audio’s current status? Have all the real dragons been slain or are some of them invincible? For example, do band-limiting antialiasing and reconstruction filters audibly degrade the signal’s time-domain information? Are there any real problems left?
Lipshitz’s presentation will be followed by a reception hosted by the AES Technical Council.