Audio Over IP

Building Pro AoIP Systems with Livewire

Steve Church, Skip Pizzi

• Publisher: Routledge
• Year: 2012
• eBook ISBN: 9781136030574
• Topic: Lingue e linguistica
• Subtopic: Studi sulla comunicazione

Position yourself at the forefront of audio and broadcast studio technology by learning audio over IP. You will gain knowledge of IP network engineering as it applies to audio applications, and then progress to a full understanding of how equipment built on Ethernet and Internet Protocol are used in today's audio production and broadcast facilities for the transporting, mixing and processing of pro-quality audio. A chapter on integrating Voice-over IP telephony (VoIP) to pro-audio and broadcast facilities is also included.

Using the popular Livewire technology, you will learn how to design, construct, configure and troubleshoot an AoIP system, including how to interface with PCs, VoIP telephone PBXs, IP codecs, and the Internet. See how AoIP systems work in practice, and discover their distinct advantages over older audio infrastructures. With its complete introduction to AoIP technology in a fun, highly readable style, this book is essential for audio professionals who want to broaden their knowledge of IP-based studio systems--or for IT experts who need to understand AoIP applications.

	CHAPTER
Introduction to AoIP	1

“IP is like Pac-Man. Eventually, it will eat everything in its way.”

—Hossein Eslambolchi, President, AT&T Labs

“Rock and roll is the hamburger that ate the world.”

—Peter York¹

“AoIP eats old-school studio audio technologies for lunch.”

—Steve and Skip

The Internet Protocol, usually simply called IP, is at the heart of the Internet. IP is the common format used for any kind of data that flows on the Internet and on private extensions of the Internet, such as the local area networks (LANs) employed in enterprise networks and small office/home office (SOHO) networks. Together with Ethernet for transport (cabled or wireless), the rules are set for the entire data networking infrastructure, both hardware and software, which has emerged from a rabble of competitors and has been so broadly embraced over the last quarter century.

IP is now driving a revolution in the field of audio studio design. It promotes a fundamental rethinking of the way signals are distributed and managed throughout the broadcast facility. Since most audio facilities have already been converted to digital, it makes sense to move on to explore the next step in the progression— transitioning to IP—as well.

Given that IP is the lingua franca of contemporary data networking, it can provide significant economies of scale for specialized applications such as professional digital audio distribution. This exploits the same process that has made the general-purpose desktop computer an efficient and cost-effective platform for the creation and storage of professional audio content. Audio-over-IP (AoIP) distribution is simply an extension of that thinking and technology, replacing the purpose-built (and relatively expensive) mixers, routers, and switchers that have traditionally been used by audio studios for managing multiple audio signals as they pass through a production or broadcast facility. IP also allows the full and continuing force of Moore's Law (which states that capacity doubles every two years) to be applied to audio distribution, just as the PC has done for recording and editing. (Anyone remember New England Digital's Synclavier? Popular in the 1980s, this audio recorder/editor/synthesizer was an impressive machine that cost its well-heeled owners over a half-million bucks. Today, a $400 PC offers teenagers much more audio production power.)

Beyond cost effectiveness, however, AoIP offers other important benefits, including:

Scalability (i.e., the ability to easily accommodate growth and other configuration changes).

Convenience (i.e., easy and fast installation).

Tight integration with Voice over IP (VoIP) phone systems, IP codecs, and PC-based applications.

Smooth incorporation of other services such as associated text and visual content.

“Future-proofing” (i.e., high likelihood of fitting well into any scenario for future facility requirements).

Putting all these elements together creates a value proposition that is hard to ignore when you are considering options for new facility designs or existing studio upgrades.

Studio audio systems using IP-based technology are now sufficiently mature to allow audio producers and broadcasters to confidently make the transition, providing them with substantial savings while simultaneously positioning them well to accommodate future needs.

1.1 TWO TO TANGO

The broadcast audio studio has a long legacy relationship with the telecommunications world. The earliest audio facilities and standard practices were developed by Bell System and Western Electric engineers in the early 20th century, and the two worlds have never strayed far from each other since.

In particular, broadcast audio has retained a close connection to the telecom environment, since so much of broadcasting's content comes and/or goes from the studio via telco-provided paths. Broadcast equipment designers also have leveraged (and continue to) the massive research and development (R&D) investment made in telecom/datacom technologies.

AT&T's U-Verse service is instructive. It is a consumer telecommunications offering that bundles TV, voice, and Internet, all of which are IP-based. Meanwhile, Alcatel/Lucent, which now owns AT&T's central office equipment business, shows no circuit-switched products on their web site, instead focusing on IP-based central office solutions. AT&T was, of course, the company that invented the circuit-switched paradigm that powered telephony since the 1970s, and served as the inspiration for traditional broadcast routing gear.

U-Verse is an example of an “IP but not Internet” application. The TV and voice services don't need to use IP, but AT&T has decided to consolidate all the services on a common infrastructure, presumably to both save money by leveraging highvolume hardware and to have maximum flexibility via IP's do-anything capability to adapt to whatever the future might bring.

It is not surprising that the next generation of studio audio technology should once again follow a path blazed by telecommunications technologies. AoIP is also “IP but not Internet,” leveraging high-volume standard hardware and offering future-proof flexibility.

1.2 ARGUMENTS FOR AoIP

What makes IP so compelling? It's “just a protocol,” right? Yes. But a protocol in the data networking context can provide tremendous value to users. At the technology level, it's simply a set of rules: the way data is assembled into packets, how confirmation of reception is communicated, etc. But to users, it means that any conforming equipment is interoperable. And because the IP protocol was designed with generality and extensibility in mind, it enables designers to create novel applications.

Although originally developed for email and file transfers, as the speed of the Internet increased, IP came to be used for media transmission as well, which is now well known as streaming media. This development has fundamentally altered the nature of how people use the Internet, and has subsequently had significant impact on all aspects of the media industry as it struggles to cope with the changes it brings and to take advantage of the new opportunities it engenders. Though the Internet's inventors were probably not thinking of streaming when they designed IP, they were thinking that keeping the core open and layered would unlock the door to a variety of applications that future creative types might dream up.

Which brings us to AoIP. While they are related, AoIP is not streaming media. Streaming is exemplified by public Internet applications such as YouTube and Pandora. There are no delivery guarantees for these services, and delay can range into tens of seconds.

On the other hand, AoIP is intended to be run exclusively on a controlled local network infrastructure. In some cases, this is just an Ethernet switch. In others, it's a sophisticated system comprised of multiple IP routers and/or Ethernet switches. In all cases, an AoIP system is designed to ensure reliable, low-delay delivery of audio streams suitable for professional applications.

1.2.1 Scalability

Perhaps the most fundamental advantage of AoIP systems over other audio technologies—analog or digital—is the ability of its underlying IP and Ethernet architectures to adapt to change and growth.

For example, a traditional audio environment must have its spatial or imaging format (e.g., mono, stereo, or surround) predetermined, along with the number of simultaneous audio channels it requires (e.g., one, two, or more). An AoIP environment has no such requirement, and can easily adapt to any audio channelization format. This applies to accommodation of any other “layers” in the system as well, such as control-data channels. In traditional architectures, a dedicated path had to be specified for these extra channels (such as RS-422 control data). AoIP systems allow such auxiliary components to be easily and flexibly carried alongside the audio payload.

Similarly, a traditional “crosspoint” audio routing switcher must have its input and output (I/O) configuration fixed in its hardware design. In this way, such a device reflects circuit switching and parallel design, whereas AoIP systems implement packet switching and serial design. The packetized, serial approach allows great flexibility and responsiveness in accommodating changes in I/O configuration.

Just as telcos have moved away from the circuit-switched paths of their earlier years for similar reasons, studio audio systems can now enjoy the same advantages of scalability and flexibility to implement expansion in any dimension. This comes not a moment too soon, given the competitive pressures coming to bear on broadcasters to accommodate increased content production and expanded audience choice.

1.2.2 Cost Effectiveness

At almost any reasonable size, an IP-based audio system will compare favorably with the cost of a traditional system—both in terms of its hardware and materials pricing, and its installation costs. The reduction in wire alone provides substantial economy.² Maintenance expenses for AoIP systems are generally also lower.

These cost differentials increase with the size of the facility, which is why so many larger installations have already moved to IP-based solutions as their needs have called for new technical plants.

1.2.3 Convenience

The small physical footprint, low operating cost, ease of reconfiguration or upgrade, and fast installation of AoIP systems make them extremely convenient for engineering and operations alike at the audio studio facility.

From initial design to implementation to daily operation, IP-based systems make life easier.

1.2.4 Smooth Integration with Other IP-Based Systems

VoIP phone systems and IP codecs can be tightly interconnected, creating numerous benefits with regard to both ease of installation and feature enhancement.

1.2.5 Talking the PC's Native Language

A lot of studio audio these days is either being sourced from a PC or being sent to one. IP/Ethernet is the PC's native language, allowing a powerful low-cost interface. Via a single RJ-45 connector, many channels of bit-accurate, high-resolution, bidirectional audio can be connected. Control comes along for the ride.

1.2.6 In the Tech Mainstream

Being in the tech mainstream means that there are a wide variety of learning resources. Books, web sites, and college courses that cover IP and network engineering abound.

Category (Cat) cables, assembly tools, RJ patch cords, jacks, testers, etc. are widely and locally available. Even some Ethernet switches and IP routers are often stocked locally.

1.2.7 Future-proofing

Nothing strikes fear in the heart of the engineer or manager more than making a bad decision on a big-ticket purchase. Moving to an IP-based audio architecture takes a lot of the pressure off, since it offers such flexibility and allows broad ability for reconfiguration down the road. Provisioning for unforeseen changes is much less problematic and cheaper with AoIP than with any predecessor architectures.

Note that the above advantages only fully apply to systems that use standard IP in their design. Not all audio systems that use computer networking (over Ethernet and/or on RJ-45 connectors) for interconnection are necessarily “true” A...

Table of contents

• Front Cover
• Title Page
• Copyright
• Dedication
• Contents
• Acknowledgments
• Preface
• CHAPTER 1 Introduction to AoIP
• CHAPTER 2 Network Engineering for Audio Engineers
• CHAPTER 3 Switching and Routing
• CHAPTER 4 Livewire System
• CHAPTER 5 Designing and Building with AoIP
• CHAPTER 6 VoIP Telephone Systems in the Studio Environment
• CHAPTER 7 IP Codecs
• CHAPTER 8 Troubleshooting
• CHAPTER 9 FAQs
• References and Resources
• Glossary of Acronyms
• Index