Pohlmann - Principles of Digital Audio - Preface

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Preface to the Fourth Edition:

At an Audio Engineering Society Convention in New York in 1984, I presented a lecture on digital audio fundamentals, using material from a course I had recently inaugurated at the University of Miami. After the lecture I was thronged by engineers seeking still more information on this new and wondrous topic. An astute acquisitions editor noted the response and in true Mephistophelean style, persuaded me to author a book on digital audio. After all, he explained, it would be easy to simply put everything down on paper. I naively accepted his bargain, and Principles of Digital Audio was published in 1985. The book's publication coincided with a tremendous surge in the research and development of digital audio technology. Virtually every segment of the entertainment, telecommunications, signal processing, and computer sciences was revolutionized, and entirely new industries appeared. Digital audio changed our lives.

Digital audio's popularity was matched only by the demand for explanations of its workings. Audio engineers, and students wishing to join their ranks, voraciously drank in every scrap of information they could find, undoubtedly further propelling development of the science. The first edition gave way to the second, which stepped aside for the third. My pact with the publisher had taken root and wrapped its twisted tentacles around my soul. As I slavishly authored one edition after another, I had only the royalty checks to console me.

When I published the third edition, I promised that I would never write a fourth edition of this title. But I unwisely left a loophole in my vow. In particular, I opined that if the technology continued to astound us with its ingenuity and there were people still eager to learn about it, another edition might be necessary. Clearly, with such a gaping hole in my steadfastness, and the continually expanding universe of digital technology, yet another edition was inevitable. With the arrival of this fourth edition, I have learned my lesson. I am not making any promises, one way or another, about a fifth.

Readers familiar with earlier editions will not be overly surprised at the extent of the renovations in this new edition. The essential nature of topics such as discrete time sampling has not changed, but our understanding of them has. Similarly, the relative importance of topics continually evolves; advances in technology diminish the magnitude of some issues, while simultaneously magnifying others. In the same way that history continually rewrites itself, our understanding of scientific principles evolves. Moreover, and even more significantly, in the five years since the last edition, entirely new digital audio applications have been developed. Most significantly, PC technology has warmly embraced digital audio, the Internet has become an audio colossus, and after years of development, DVD and DTV have been launched.

Examination of this new edition will show that perhaps one-third of the text has been revised and new text and illustrations have been added. A number of topics have been eliminated to conserve the page count (and cost), a number of discussions have been significantly expanded, and a variety of fresh topics, both theoretical and practical in nature, have been introduced. Readers will find much timely material (and many new acronyms). PC audio topics include IEEE 1394, USB, AC '97, and DirectX. Internet audio topics include MP3, SDMI, and RealNetworks G2 streaming audio. Low bit rate topics include MPEG-2, AAC, MPEG-4, Dolby Digital, and PAC. DVD topics include DVD-Video, DVD-Audio, recordable DVD, UDF, and MLP. Television and radio broadcasting topics include ATSC DTV, AM-IBOC and FM-IBOC (including USA Digital Radio and LDR prototypes). New compact disc topics include CD-R, CD-RW, and Super Audio CD. Harder to pigeonhole topics include new AES standards, jitter, sound cards, data compression, digital audio extraction, and watermarking. Similarly, the bibliography has been updated and expanded.

As much as possible, a user-friendly approach has been retained, but the greater depth given to some material has increased the reading sophistication required. Also, inevitably, increasingly more sophisticated technologies such as DVD require more complex descriptions. Of course, readers may pick and choose according to their level and need. Also, the wider scope of topics should better satisfy a broader range of professional practitioners and students. The former will notice an increased emphasis on applications-oriented material.

One thing has not changed. This book is neither a compendium of every possible fact nor an advanced treatise. It is an introductory text that attempts to provide the most lucid explanations possible, and to strike that all-important balance between mere information, and understanding. In other words, this is a learning tool, brought to you by someone who enjoys spending time on both sides of the lectern.

The material in this book stems from the work of the many pioneers and leaders in the field of digital audio technology. We owe a tremendous debt to those enormously creative and hard-working engineers who breathe life into the science of digital audio. Clearly, their vision of the potential of this young science has profoundly changed both our industry and society.

A final note: in the same way that Faust enjoyed the rewards of his pact with the devil, I hope you find the latest installment of this book to be very rewarding. Whether you create, teach or learn about cutting edge technology, you know exactly what I mean.

Ken C. Pohlmann
Coral Gables, Florida