Books of a technical nature suffer from a number of problems. Perhaps the most obvious is that technology progresses. What was once considered best practice in a particular field, may be regarded with derision at a later stage. Furthermore, recognized practices were once not recognized, whilst a book remains as a permanent record.
This book is about the transfer of audio data and other audio related data, over digital communications networks, and it is published at an exciting time for this specialist area. Although the Internet has made networks the property of the people, there were not previously the data rates available at the right cost to transfer the quantities of data (quantities that seemed impossible ten years ago, but will be shrugged off in half that time) required for professional audio use.
At the same time that data rates improved through advancements in the communications industry, the audio industry also looked for flexibility in transferring digital audio and control data. The meeting of technologies has produced a number of initiatives, specifications, and standard agreements aimed at audio applications. At the time of writing, no clear industry standard had emerged, although the collective works are available across a range of audio applications.
This book presents as many of the candidates as possible, with the provision that new initiatives emerge regularly and that current work is constantly updated, amended, improved or otherwise changed – to reflect the latest technology progression or recognized practise. To this end, further reading sections are supplied to help the reader seek out the most current information. Where possible, Internet addresses are supplied to help speed the process, although since these are subject to change, the postal address is also provided. On occasion, subject matter is included only to expose its presence, and since technology progresses, these may or may not be included in any audio future.
Another of the aforementioned problems of technical books is the tendency towards jargon, especially acronyms. Although no apologies are made for the use of acronyms, as to repeat the words verbatim at each appearance in the text would win praise from no one, sympathy is offered instead!
In defence, one of the goals of this book is to introduce digital communications to those already familiar with analogue theory. It is necessary therefore to create a foundation of concepts, terminology, and methods upon which to build knowledge. This is especially so since digital and analogue communications techniques, whilst apparently performing the same task, operate in a completely different fashion.
The first of the concepts that is introduced is the modular approach of the International Standards Organization open systems interconnection 7-layer reference model. This is simply a conceptual model designed to communicate and illustrate the steps required to achieve useful interdevice communications between two points, over a complex path (or network).
A useful by-product of including the 7-layer model is the useful introduction to conceptual models as a whole. Several of the technologies presented herein use their own established conceptual model to illustrate their methods. So-called ‘technology evangelists’ will insist that a particular technology does not fit into the 7-layer model and so a new conceptual model was created. On the whole, such a claim is misrepresentative since usually it is the case that the new conceptual model serves to focus in on a particular area of functionality within the 7-layer model, expanding and detailing that area. This is because the 7-layer model is such a general overview of areas requiring attention, whilst the conceptual models associated with particular technologies offer detailed descriptions of particular implementations.
Finally, it was a struggle to visualize who would find use for a book that spans the data communication and audio engineering fields. As it happens, this is now a very fast moving technological field, although it this has been an interest of mine since the early days of my audio training, as the following narrative, kindly supplied by my good friend Robert C. Alexander, illustrates:
Andy Bailey and I had been living and working in Australia for nearly a year when walking back from the recording studio in October 1990 one night, our discussion turned to the possibilities of the future of the audio industry.
These were the days when digital data transfer, ISDN, and mass information communication used as tools for the audio industry were in their infancy. Even the Internet was yet to make an impact. Just months earlier, the first murmuring of digital audio transfers between studios were being heralded. Indeed, digital recording itself was still a novelty.
We discussed the exchange of massive amounts of information between one point and another, allowing audio data and even video information to be exchanged freely and easily to anybody and everybody connected to a huge central communication system. No longer would artists need to fly at great expense all over the world to record albums in Los Angeles, London, New York, or Sydney. It could be done from the local recording facility using new communications technology. Entire mixes could be done from remote locations utilizing the engineers and producers most suited to the job, yet without them ever having to leave the facility in which they most preferred to work.
This represented a massive (and at that time unattainable) leap forward for the audio and computer industries, which had, as yet, to wake up to ideas such as the Internet. There were no publicly available communications systems that were fast enough to handle the amounts of data we were imagining; whilst user interfaces which could be accessed by everybody from audio engineers to laymen were over four years into the future. In hindsight, an amazing two hours saw us cover topics that we realized could happen, if they could be imagined by us.
In the years that followed, after returning to England, Andy pursued a different branch of the industry to myself, concentrating on technical education whilst I concerned myself with audio engineering, education, and writing. I had no hesitation in getting Andy involved with writing and I was justly rewarded with a continual flowing stream of articles that first brought the name Andrew Bailey to industry awareness. It came as no surprise to me when he was commissioned to write this much needed reference book for the audio industry.I have no doubt that this complex subject will become one of the key elements in bringing the communication and information age that the twenty-first century promises, to the audio world.
This book is an extension of the conversation Andy and I had, a decade ago, walking home in Sydney.
Andy Bailey