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The September 10, 2009 Issue Provided by System Dynamics Inc.
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Audio Video Bridging -- The Missing Link In Home Networking

When we visited the Broadcom suite at CES in January 2009, Senior Technical Director Yong Kim showed us their work on "Ethernet Audio Video Bridging". The demo showed how AV bridging made it possible to carry multiple high-speed media and data streams over the same Ethernet link. With standard Ethernet, TV pictures would have broken up, and audio would have stuttered; with AVB, all the streams were delivered perfectly, with no interference.

The more we thought about and researched what we had seen, the better we understood how truly important AV Bridging is to the vision of interconnecting the whole broadband home. Many new applications will work only if AVB is included in all networking technologies deployed in the home.

AVB is a high-level QoS standard designed to be applied across all networking technologies. Until now, the absence of such a standard has made it necessary to partition the home into multiple technology islands to keep various media and data streams from interfering with each other.

AVB provides the missing link required to interconnect the technology islands. When fully implemented, homes will have a unified network for data and media, enabling a wide variety of innovative applications.

AVB Connects The Islands

Different networking technologies have been applied to solve particular problems, creating separate "islands" of digital technology. One island--based on Ethernet and Wi-Fi--is used for data networking between PCs and the Internet. Another--based on HDMI--is used to connect video sources such as DVD players and set top boxes to TVs. A third--based on coaxial cable with MoCA or HomePNA--connects master DVRs to remote set top boxes. Because these streams of media and data are kept within islands where they can't interfere with each other, all the streams run at the highest quality.

Emerging applications require connections between the islands. Users would like to play PC video on their TVs, and would like to connect TVs and set top boxes to the Internet. Ethernet would be the logical way to interconnect these islands. Lacking QoS, standard Ethernet cannot keep data traffic from interfering with media streams, and cannot guarantee that audio and video will stay in synch.

The consumer electronics industry has wanted to address Ethernet's limitations for many years. John Gildred, then VP of Engineering at Pioneer Research Center USA, a division of Pioneer Electronics, described the problem in a session we organized and moderated at the FastNet Futures conference in March 2004. John said that although Ethernet operates at very high speed, it's "best efforts" only. Video transfers "break up" when other applications, such as a video download or a PC-to-PC file transfer, run simultaneously on the same Ethernet network. Until this problem is solved, Ethernet can't be used for consumer electronics video applications, such as playing a video on a DVR in one room and carrying it over Ethernet to a TV in another room.

More than five years later, AV Bridging provides the solution to the problem John laid out. It adds delivery guarantees to Ethernet, making it possible to carry media and data over Ethernet with no loss of quality. It does even more, providing a high-level mechanism for end-to-end QoS over diverse networking technologies. Once implemented broadly in home networking technologies, it will be possible to carry multiple streams of high-definition video and high-quality multichannel audio over the same network being used for high-speed data.

Yong Kim's demo showed how this works in the real world. It included several different media sources: a DVD player, an MP3 player, and an electric guitar. These media sources were all connected over a common Ethernet link to corresponding media players: a high-def TV, a digital audio player, and a guitar amplifier. At the same time, the Ethernet link was carrying a high volume of data traffic from a traffic generator (like your teenager downloading video). Yong showed us a diagram of the setup:

Diagram of EthernetAV --> Click for larger picture

The audio and video in Yong's demo all played perfectly, showing that AV Bridging over Ethernet made it possible to carry intermixed media and data with perfect QoS and precise time synchronization.

The Audio/Video Bridging Task Group

The Audio/Video Bridging Task Group is devoted to providing the missing link. Formally under way for more than five years, it has undertaken to solve the most difficult remaining problem for the broadband home: making it possible for multiple digital media streams to get from any source to any destination over any combination of networking technologies with no loss in quality.

The AVB task group was originally formed as part of IEEE 802.3, which is responsible for Ethernet standards; John Gildred was one of the lead presenters in the Call For Interest in July 2004. It soon became clear that the problem was more than Ethernet, and a year later the group moved to IEEE 802.1, responsible for "bridging" -- the protocols that cross-connect between all types of devices.

Four New Standards

The AVB group is coordinating the development of four new IEEE standards, which provide precise timing, bandwidth reservation, and guaranteed low latency. These new standards, on track to be completed by 2011, will be implemented in Ethernet chips and incorporated in new consumer and professional Ethernet devices.

The new AVB protocols are independent of any particular type of Ethernet. Fast Ethernet (100 Mbps) is most common in homes today. Gigabit Ethernet (1 Gbps) has reached consumer price points, and 10 Gbps Ethernet is already on the enterprise market.

These bridging mechanisms go beyond Ethernet--they have been designed so they could be implemented with any 802-type protocol. All the newer home networking technologies (Wi-Fi, HomePlug, MoCA, HomePNA, UPA, etc.) include some form of QoS and other mechanisms designed for high-quality media transport. AVB provides a common high-level mechanism for end-to-end QoS across all these technologies.

A View From the Plumbing Architect

Mike Teener, AVB Chair and Broadcom Plumbing Architect --> Click for larger pictureMichael Johas Teener, Technical Director / Plumbing Architect at Broadcom, has chaired AVB throughout the effort. Mike has been dealing with these issues for a long time. As Plumbing Architect at Apple Computer, he was the chief architect of Firewire, and has been chair or editor for three IEEE 1394 standards. He joined Broadcom in 2005.

In mid-March, we interviewed Mike over the phone to learn more about AVB. We observed that DLNA uses Ethernet at its primary physical layer, and evaluates the other technologies against Ethernet. So we asked whether AVB was solving a real problem. He said "You can't build digital speaker systems because there's no way to synchronize the streams--you can't do multiple streams. There's no concept of timing in standard Ethernet. My son downloading music or playing internet games interferes with video. In addition, the content providers are pushing DLNA to have managed QoS; virtually every carrier has said they want QoS."

We asked him how soon we're likely to see AVB in products. He said "several major companies that provide silicon are part of this project. The professional AV business needs it, and will start rolling it out this year. The CE companies will come in at the higher end, the rest on an as-needed basis. There are no technical disagreements between the standards participants; little in the protocol stack needs additional work. Chips and products will be coming out quite soon, compliant with the draft standards. There will be some low-cost chips this year."

We mentioned the Broadcom demo at CES, and asked whether AVB was already incorporated in some chips. He said "Parts that have early AVB capabilities have been out for a year and a half. Chip makers usually wait until sponsor ballot to announce and one of the three major standards was just approved for sponsor ballot. AVB will become part of the 802 standard and nobody will do Ethernet chips without it. Before AVB there was nothing for applications that needed professional quality QoS to hook to; we're setting up the structure so people can hook the layer-2-specific QoS mechanisms to a common middle layer. That way there's just one piece of firmware to write."

Finally, we asked Mike about the implementation of AVB in other networking technologies. He said "We’ve had representatives from virtually every layer-2 technology participant: 802.11 has a dedicated group working on video streaming using AVB interfaces, and MoCA, HPNA and even will embrace AVB. A long list of silicon companies made a contribution to requesting that AVB be part of their assumptions. The ITU (’s sponsor) demands interoperability, and AVB solves the QoS interoperability problem."

We recently talked on the phone with Chano Gomez, Vice President for Technology and Strategic Partnerships at DS2. He confirmed that the specifications, which will be completed this year, will include support for AVB. He said "we have all the elements in so that it can run AVB," with most of the AVB specifications contained in a mandatory annex.

BroadSync HD Technology

Given Broadcom's strong push on AVB, it was no surprise that mid-March brought the announcement of BroadSync HD technology. The announcement said BroadSync HD would "enable extraordinary streaming of high definition (HD) audio/video (A/V) traffic over Ethernet to networked electronic devices. ... BroadSync HD technology is Broadcom's custom implementation of the AVB draft standard.

"Broadcom is leading the effort to promote the AVB draft standard, which uses standard Ethernet connectivity (i.e. Category 5 cabling and RJ45 connectors), as the common underlying technology for high quality network-based streaming that will eventually replace most other types of connectivity presently used in A/V equipment."

The AVnu Alliance

Late August brought yet another AVB announcement: the formation of the AVnu Alliance. The press release said "The AVnu Alliance aims to establish a professional quality A/V experience in networked environments, whether an HD television or music studio, a car, a concert hall, a stadium or a home theater. ... The founding members ... include Broadcom Corp., Cisco Systems Inc., Harman International, Intel Corp., Samsung Electronics Co., Ltd., and Xilinx, Inc."

While AVB's roots are in Ethernet, AVnu advocates the use of AVB to provide "professional quality A/V" over all lower-level networking technologies "to ensure reliability in a heterogeneous network based upon open industry standards". AVnu expects to play a role for AVB similar to the role the Wi-Fi Alliance plays for IEEE 802.11: compliance and interoperability (C&I) testing, and promotion.

Rick Kreifeldt, Avnu Chairman and Harman VP --> Click for larger pictureTo learn more about AVnu (pronounced like "avenue" without the "en"), we interviewed Rick Kreifeldt, AVnu Alliance Chairman and President. Rick's "day job" is VP of the System Development and Integration Group at Harman International, a long-time leader in professional, automotive and consumer electronics. (Dave told Rick that he knew Harman well - his very first paycheck from his first job out of college went to buy a stereo system based on a Harman-Kardon amplifier and pre-amp.) Rick has worked at Harman for close to 16 years, mostly on the professional side, and now runs an advanced R&D group which works on AVB, cutting across all three Harman market segments.

Rick said AVB would be applied first in the professional AV market. "If you look at large stadiums or convention centers, they're doing AV streaming using proprietary technologies. It takes a lot of engineering to hold it together. Hitting latency is hard; and a little bit of traffic can interfere with streaming." He said the alliance is reaching out to players in the other markets "The companies that are involved in AVB understand what’s going on in the ecosystem" and pointed out that the founding members included such major players as Broadcom, Cisco, Intel, and Samsung as well as Harman.

Harman Professional has already started showing products based on Ethernet AVB. At an industry show in April, Rick demonstrated a digital matrix processor and amplifier connected through an Ethernet AVB switch. In his talk about AVB at the show, Rick said "Harman has long been a very active participant in this group and we’re very pleased to see the momentum this initiative has generated from such a diverse host of technology companies."

The Resource Library on the AVnu website currently includes four white papers. "No-excuses Audio/Video Networking: the Technology Behind AVnu" is an overview of AVB technology by Michael Johas Teener. Individual white papers cover the three markets: automotive, consumer electronics and professional A/V.

Automotive is perhaps the least obvious application of AVB. In the automotive white paper, Rick and his co-authors describe the various forms of data and media in cars today, and the complex problems designers face in integrating audio, video, control and diagnostics over the wiring buried in the car. AVB would make it possible to use Ethernet for all the links.

Whole Home Networking With AVB

We have long written about "whole home networking"--a unified network for all data and media traffic in the home. We have always believed that no one technology would provide everything needed, and that a combination of technologies would be required.

End-to-end QoS is an essential requirement for whole home networking. But until AVB, QoS has been missing in Ethernet. Wi-Fi and the wide variety of exiting-wiring technologies all use different approaches for QoS.

AVB is the missing link. It provides the framework to solve the last major outstanding issue in the Broadband Home. It will be incorporated into all future Ethernet devices. Work is already underway to incorporate it into Wi-Fi and

The next generation of industry-defined existing-wiring technologies (MoCA, HomePlug, UPA) are now on the drawing boards. To fulfill the vision of whole home networking, we hope AVB will be an integral part of all these technologies.

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