University of Toronto
Department of Computer Science

A Distinguished Lecture on Computer Science

Jim Snyder

AT&T Labs Research

MPEG Advanced Audio Coder: An Overview


During the last three years an obscure signal compression technology known to the technical world as MPEG layer 3 has become a household term: mp3. mp3 and its sister algorithms, which attempt to preserve the fidelity of the original music recording while carrying that signal in fewer bits, have made it practical to distribute music recordings over the network, and in doing so have called into question long-held views of ownership of intellectual property.

In this overview talk I will discuss the principles underlying most modern audio coding algorithms, as exemplified by the MPEG Advanced Audio Coder algorithm, the successor to mp3 (at least in the technical world). I will compare AAC performance with the performance of other audio algorithms, and will demonstrate audio coding at various bit rates using AT&T's AAC implementation.

In the second half of the talk, I will discuss the effect of packet loss on compressed audio data streams, and demonstrate the effectiveness of simple strategies for concealing packet loss. Using this as a starting point, I will discuss an IETF draft which uses error concealment as a form of bandwidth control. Time permitting, I will demonstrate Verdi, a multimedia streaming system developed at AT&T Labs Research, which uses AAC as its preferred audio compression technology.


Jim Snyder is a Technical Consultant at AT&T Labs Research, where from 1995 through 1999 he managed projects involving compression and network distribution of music. He is not entirely sure what he's working on now, but it appears to have something to do with ATM switching and home networking. To relax and get away from it all, he is setting up a networked music jukebox and networked audio endpoints at home.

Mr. Snyder has a BA from Rice in 1972 (math/physics) and a PhD in 1978 from Yale where he worked in high-energy physics. From 1979 thru 1996 his principal research interests involved the design of general-purpose and signal processing computers. He was general chairman of the first IEEE Workshop on Applications of Signal Processing to Audio and Electroacoustics (1986), chaired the IEEE SP Society's Audio Technical Committee from 1986 to 1989, and was an associate editor of IEEE Transactions on Speech and Audio Processing. He has published on a variety of topics (see for example the April 1997 paper, and has been awarded numerous patents.

Host: contact Prof. Schraefel for information on the speaker's schedule.

Time and Location: Thursday, March 8th, 11am, GB119.

R. J. Miller
Last modified: Thu Feb 22 08:24:51 EST 2001