A Peek Into MP3’s Past

9/8/2009 11:39:59 AM
By PSN Staff
 David Schwartz
By Dan Wolfson.

This year’s AES Convention marks the 25th anniversary of the publication of two watershed technical papers that, in conjunction with the work of the man who inspired the content of those papers, would ultimately change the entertainment industry as it was known then, and lay the groundwork for the digital entertainment landscape of today.

The papers were “High Speed Telecommunications Interface for Digital Audio Transmission and Reception,” by Hyun Heinz Sohn, which outlined a high-speed (for the time) 56kb digital interface for AT&T’s Accunet system; and “Strategies for the Representation and Data Reduction of Digital Music Signals,” by John Stautner, which discussed reducing algorithmically the size of music files to facilitate their transmission and storage. Boil down the academic jargon and you’re looking at the blueprint for downloading music.

But what sparked these presentations was the work that had been done by David Schwartz, a one-time garage-band bassist-turned-engineer/entrepreneur. At his home in Denver, Colorado in 1982, he had been playing keyboards directly into his Apple II computer, using an 8-bit Mountain Computer keyboard synth interface. Before MIDI came into the picture, the Apple II recorded his keystrokes and let him layer various sounds. It led to an epiphany: “I was playing back from 5.25-inch floppy disc and one day I realized something: I could get 20 minutes of live music onto a 135-KB floppy, while a CD, which holds around 700 MB, that same 20 minutes takes up 300 MB. There was a disconnect there.”

Schwartz posed the question to himself: what’s the difference between natural sound recorded digitally, and synthetic data of that music? “That got me going on audio compression,” he says. “There had to be a way of representing music with fewer bits.”

Schwartz’s work creating a DSP-based algorithm for compressing music data files led, ultimately, to U.S. Patent No. 4,472,747, awarded on September 18, 1984, described as “a microcomputer system for converting an analog input signal, such as an audio signal representative of sound into a digital form for storing in digital form in a highly condensed code and for reconstructing the analog signal from the coded digital form is disclosed. The system includes reductive analytic means where the original digital data stream is converted to a sequential series of frequency spectrograms, signal amplitude histograms and waveform code tables. Approximately 100 times less storage space than previously required for the storage of digitized audio signals of high fidelity quality is thereby obtained. Additive synthesis logic interprets the stored codes and recreates an output digital data stream for digital to analog conversion that is nearly identical to the original source material.”

The next imperative would be implementation. Working out of his home, Schwartz’s research into digital signal processing led him to Texas Instruments’ newly introduced TMS32010 chip, which could perform fast-Fourier transforms (FFT) in real time. But to attain useful software for the codec, Schwartz realized he needed to bring in other minds. Assigning his patent to his newly formed company CompuSonics, Inc., his attorney guided him to Mike Wolf, a researcher at the government labs at Los Alamos, New Mexico, who developed a filter bank and collaborated with him on what would become the first solid-state digital audio recorder in 1983. Schwartz reached out to graduate researchers John Stautner at MIT (who would become a vice president at CompuSonics) and Gary Schwede at UC Berkeley, who helped refine the codec and the transmission schema.

This was all taking place well before the establishment of MPEG as a file standard, which was approved by the International Standards Organization (ISO) in 1991, based on formats developed by AT&T-Bell Labs in the U.S. and the Fraunhofer Society for Integrated Circuits in Germany. The first commercial applications of the MPEG audio layer 3 codec (MP3) didn’t take place until 1994.

“All audio data compression in 1983 was basically used for telephony,” Schwartz recalls, adding that the PCs of the time weren’t sufficiently powerful enough to handle the company’s evolving codecs. “We had to design our own computers.”

This all came together at the 76th AES Convention in New York City in October 1984. CompuSonics introduced its digital audio recorders, the DSP1000 consumer model and the DSP2000 professional version, which used the same 16-bit A-D converters as the Sony 1610 digital tape recorder. The concept of Heinz Sohn's high-speed telecommunications interface for digital audio transmission was also introduced, though a working demonstration of transferring audio over phone lines had to wait until the following year, when CompuSonics sent music from Chicago to the AT&T headquarters in New York City, an industry first.

Ultimately, CompuSonics failed to leverage its patents or its products into profits. But the ensuing rewards for science, industry and consumers were rich and continue to this day. Schwartz’s key patent was the grandfather to the notion of music downloads, which boosted the PC industry and gave rise to an entirely new generation of personal music players--imagine a world without iPods and iTunes. The same technology that came to threaten the music industry ultimately would also provide its means of salvation.

Schwartz, now president of Schwartz Engineering & Design, has been awarded a dozen U.S. patents, has worked with Tandy Corp and Atari developing new digital audio platforms, and will introduce a “revolutionary” new microphone technology at the AES Show in New York this month, displays equanimity about his place in digital audio history. “It was humbling experience,” he says of the mechanics of format monetization, “but it was the basis for an entirely new generation of entertainment technology, and it’s a good feeling to know you contributed to starting it.”

For a look into technology Schwartz is introducing at this fall’s AES convention, watch for the blog post, “Smoke and Lasers,” in the coming days.

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