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Sound Connections in Audio Networking

The world of networked AV is its own kind of Babel. CobraNet, developed by Peak Audio in the mid-1990s and the first successful digital audio networking protocol, had a shot at becoming an industry standard. But while its acceptance by the pro audio industry was fast, it wasn't fast enough to outpace a host of other companies. We look at four of today's prominent protocols.

Whither Ethernet AVB?

Ethernet Audio/Video Bridging (AVB) gives the networked audio market what it ultimately needs: an IT-level traffic cop. Generally speaking, Ethernet protocols on the market can't transfer low-latency, properly synchronized, high-quality media across a local area network (LAN) without other data traffic interfering.

Ethernet AVB, developed by the IEEE AVB 802.1 AVB Task Group, provides three major enhancements to 802.1-based networks: precise timing to support low-jitter media clocks and accurate synchronization of multiple streams; a simple reservation protocol that allows endpoint devices to reserve the bandwidth in a path to guarantee quality of service (QoS) for audio/video streams; and queuing and forwarding rules that ensure that AV streams will pass through the network within the delay specified. The bottom line: Ethernet AVB fast-tracks designated audio data streams into a higher-priority class of packet that are expedited ahead of standard, "best-effort" data traffic.

On a more technical level, AVB tells the network that audio and video are fundamentally different from other data. "All of the current [proprietary] protocols deal with the endpoints of a network, not the network itself," explains John McMahon, executive director of digital products at Meyer Sound. "In between, at the routers and switchers, the needs of time-sensitive AV information can find the network to be pretty hostile territory. Ethernet AVB addresses that."

Ethernet AVB requires all-new hardware but remains backward-compatible with existing Ethernet standards. However, the enhancements enabled by IEEE 802.1 standards require no changes to the Ethernet lower layers themselves and are compatible with all the other functions of a standard Ethernet switch. As a result, the entire Ethernet ecosystem is available to developers.

Rick Kreifeldt, vice president, systems architect at Harman, which has been a staunch AVB backer, says it's the protocol's open standards and scalability that will give it the kind of price points needed to bring networking to the vast and expanding pool of smaller AV projects. "Even CobraNet, which has the greatest reach of all of the systems, is still relatively costly and complex and not really scaled for much of the work in the AV market today," he says. "And without scalability to that degree you don't get the kinds of economies of scale that can really drive networking." AVB, on the other hand, he says, is structured in a way that encourages development by numerous third parties to extend beyond the install market and into consumer and automotive sectors.

Ethernet AVB has the potential to become a standard for several reasons. For starters, the protocol is backed by huge consumer audio players, such as Apple and Samsung, which will drive much broader demand for AVB-compliant products. Samsung, Intel, Cisco Systems, and other companies have formed the AVnu Alliance, a trade group to promote the protocol.

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