Bridging the Gap

The forthcoming 802.1 Audio/Video Bridging standard promises to make networked audio and video easier to configure and better to use. Tim Kridel finds out how.

AV and IT have spent most of this decade converging, producing a variety of new technologies and standards along the way. The latest example is 802.1 AVB, a trio of standards aims to make networked audio and video easier to set up and more likely to provide a better user experience.

Short for Audio/Video Bridging, AVB is a subset of the Institute of Electrical and Electronics Engineers’ (IEEE) 802.1 standards work for local, metro and wide-area networks (LANs, MANs and WANs). What all that means is that AVB will be a set of open, industry-wide standards instead of a proprietary technology controlled by a single company.

AVB’s main goal is to minimise gremlins such as jitter, pixelization and out-of-sync audio and video. It does that by prioritising the audio and video packets ahead of other traffic that’s less sensitive to delays and by setting aside bandwidth for each AV stream.

In the process, AVB puts more control in the hands of integrators and reduces their reliance on IT vendors or a client’s IT department, both of which might not know or care about the nuances of audio and video.

“That’s a huge paradigm shift for networked audio because up ’til now, it’s been a battle to get your packets through on time,” says John McMahon, executive director of digital products at Meyer Sound, which will start shipping AVB products this fall. “When we go into an install, we’re not going to be dealing with network infrastructure vendors who know nothing about flavor x, y or z of audio networking.”

Inside the Standard

If AVB’s goals sound familiar, it’s because some of them are achievable today using, for example, proprietary technologies. Those exist to make up for the shortcomings of IT networks, which typically lack mechanisms that would be helpful for ensuring audio and video quality of service.

For example, although those networks have the native ability to determine when packets have been lost and need to be re-sent, they can’t guarantee that all of the packets will arrive on time to in order to avoid problems such as jitter. So AVB focuses on providing the mechanisms that enable those and other guarantees.

Take latency. AVB is supposed to enable 2 millisecond over seven hops within a network but without the need for lots of buffering.

“The way we get low latency numbers in AVB is because we know what the throughput time is on a switch,” says Rick Kreifeldt, vice president of the system development and integration group at Harman Professional. “That’s incredible to know. And if I know that, and it’s a guaranteed number, I can guarantee end-to-end latency that’s much lower because I don’t have to buffer and wait.”

“The way we get low latency numbers in AVB is because we know what the throughput time is on a switch,” - Rick Kreifeldt

The IEEE 802.1 AVB Task Group achieved that and other features largely by adopting and adapting parts of existing standards and vendor-specific approaches for ensuring quality of service (QoS).

“It turns out that remarkably little has to be done [to accomplish that],” says Michael Johas Teener, a technical director at Broadcom and chair of the IEEE 802.1 AVB Task Group. “We just had to standardise a whole lot of things that people do to make things work. I can’t to any particular thing that’s utterly unique in AVB if you look at various proprietary implementations or other standards.”

AVB also aims to create an ecosystem of intelligent devices communicating with one another in order to handle QoS-related tasks. That’s supposed to free both the integrator and end user from having to understand the nuances of what’s going on under the hood.

In the process, AVB is supposed to make Ethernet a viable option for more AV installations.

“For the average person, smaller things, they haven’t been able to realise the benefits of simpler cabling,” says Harman’s Kreifeldt. “They’ll be able to realise that because the costs are going to be much lower than CobraNet.”

AVB is best suited for LANs rather than WANs because once the audio or video stream hits a router, such as the border between a LAN and WAN, AVB’s domain ends.

“This would work great in a LAN because that’s switch-driven,” says David Hsieh, vice president of marketing for emerging technologies at Cisco. “But the minute that you have to go to another network, and therefore you need a router, then AVB doesn’t address that.”

In those cases, one option might be to have the WAN network use a standard or vendor-specific technology that complements AVB by providing QoS mechanisms in between the two LANs that use AVB.

Where are the products?

IEEE members probably won’t vote to approve AVB until early 2010. (For updates, visit However, the standards work is close enough to being finished that vendors such as Meyer Sound are already building products based on the near-final version.

“The intent is to make sure that everything is in sponsor ballot by first quarter 2010,” Teener says. “We don’t anticipate a lot of controversy. It’s not like 802.11n [Wi-Fi], where you’ve got lots of people fighting over stuff. We’re not fighting. We’re just trying to get it right.”

AVB is focused on what’s called Layer 2 in networking-speak. That means it resides in switches rather than routers, so those nodes must support AVB. Depending on the switch’s design and age, AVB could be added via a firmware upgrade instead of requiring the client to buy new, AVB-compliant switches.

“If there are three switches in between two D-Mitri devices [Meyer Sound’s AVB-compliant Gigabit digital audio processing and distribution platform], for instance, all three need to be AVB-compliant,” McMahon says. “There can be non-AVB-compliant switches connected to those switches, but there has to be a path between all of the AVB devices that is an AVB-protected path.”

But most switch vendors have been mum about when and how they’ll support AVB in both existing and forthcoming products.

“So far, there’s a lot of innuendo,” McMahon says. “But side conversations have indicated that the hardware capacity that is needed to implement these new versions of firmware has existed in a lot of switches for the past couple of years.”

Endpoints also must support AVB. As with switches, there’s the wild card of how vendors will add that support. For example, if an existing endpoint has enough processing and memory “headroom,” the vendor could add AVB via firmware. Another option is to use adapters to add AVB functionality to legacy gear.

Yet another option is to buy new equipment, whether it’s switches or something else. It’s here that the economy could help AVB build a presence in the marketplace: When the rebound really kicks in, enterprises that had been trying to wring a few more years out of their switches and other equipment could be receptive to buying new gear.

If that rebound is in full force by mid-2010, there could be at least a basic selection of AVB-compliant gear. A few products already have been announced, such as Meyer Sounds’s D-Mitri.

“We have a pretty extensive road map of products that we are going to AVB-enable,” says Harman’s Kreifeldt.

But the real barometer could be the Consumer Electronics Show (CES) in January 2010. That’s because although AVB benefits pro AV, it also has a strong consumer play. The more AVB products announced at CES 2010, the more chipsets and other components available to pro vendors. Consumer also has higher volumes, which benefit pro by driving down the cost of AVB.

AVB also fits in with business-to-consumer (B2C) applications. For example, suppose that a cable operator offers its customers an AVB-enabled home videoconferencing system. That system then could connect to a bank’s AVB-enabled desktop conferencing system when consumers need to interact with their financial advisors. Cisco is among the vendors eyeing B2C applications, which it’s already targeting with AVB-like platforms such as Medianet.

“We’re excited about the potential to leverage 802.1 AVB in the home and connect it to an enterprise or service provider Medianet to enable end-to-end quality of experience,” Hsieh says.

Vendor support also depends on the cost of adding AVB to equipment. None of the companies interviewed for this article would provide a ballpark estimate, partly because they and their rivals are just now implementing it. But most agreed that the cost would be minimal.

“It’s no more than putting in a CobraNet interface and at this point probably quite a bit less,” says Meyer’s McMahon.

Standard caveats apply

When a standard debuts, it often comes at the expense of an existing technology – if not initially, then eventually. In AVB’s case, CobraNet appears to be the one with the most to lose.

“I wouldn’t invest heavily in any of those proprietary technologies at this point,” McMahon says.

Like any other standard, AVB aims to make it easy to mix and match equipment from different vendors as long as those products are all built to the AVB standard. And like any other standard, AVB runs the risk of interoperability problems caused by extra features that vendors layer atop the standard to differentiate their products. That’s something for integrators to be aware of when comparing different vendors’ AVB-compliant products.

Another wild card is that not all vendors implement every part of a standard, and AVB likely won’t be the exception to that rule. That’s another variable that integrators should watch for, particularly in the first year or two after AVB enters the market.

“I imagine that there will be a little bit of a shake-out period where different companies might implement different parts of AVB, so there’s a little of that profile matching that might have to shake out in the marketplace,” says Cisco’s Hsieh. “Somebody might say, ‘I’m 802.1 AVB-compliant,’ but they’ve implemented only one specific piece, so they have a very limited profile to offer. That might not provide a huge amount of value.”

All of those variables could create an ironic situation, at least in AVB’s first few years: Although the standard is supposed to help enable multi-vendor interoperability, some integrators and end users might prefer to stick with a single vendor’s AVB products to avoid problems related to extra features outside the standard and incomplete implementations of the standard.

For now, some vendors say they’re getting good feedback from the integrators and business partners that they’ve introduced to AVB.

Says Kreifeldt, “The thing I get the most is, ‘I can see how this all comes together without me having to do so much work.’”

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