Audio Networking: Broadcast Sound on the Move, Part 2 — Open Standards
Although proprietary audio-network products have garnered a lot of attention in the growing market for networked audio-signal transport, standards-based approaches are also on the table.
AVB (Audio/Video Bridging) looks to make its first significant impact in 2014, with a number of compatible products coming from AVnu Alliance’s 60-odd members through the university-based testing process necessary for the AVB stamp of intercompatibility approval. According to Sheldon Radford, senior product manager, live systems, Avid, and that company’s liaison to the AVnu Alliance, the long wait from announcement to product reality for AVB-compliant products is due to the thoroughness implicit in IEEE standards-based vetting, but they will have been worth the wait.
“There are benefits, such as guaranteed playout synchronization between points on a network and the fact that an open-standards approach tends to have a very long shelf life,” he says. “AVB leverages the ubiquity of Ethernet infrastructure and will be around for a long time to come.”
Even newer is the AES67 protocol, announced in September, which establishes interoperability standards for interoperability of networked/streamed audio-over-IP. It was created to address the fact that, although there are networked-audio products and systems developed to support high-performance media networking, until now there have been no recommendations for working with these systems in an interoperable manner — that is, allowing various components of systems from different manufacturers to work together in a single system. AES67 provides comprehensive interoperability recommendations for synchronization, media-clock identification, network transport, encoding and streaming, session description, and connection management.
The AES67 standard addresses high-performance media networks that support professional-quality audio (16-bit, 44.1-kHz, and higher) with low latencies (less than 10 milliseconds), and at a level of network performance that can scale from local-area to enterprise-level networks. In contrasting a standards-based approach with proprietary ones, Says Kevin Gross, owner of Denver-based digital network consulting firm AVA Networks and leader of the AES work group that developed AES67, “The proprietary systems on the market now are like black boxes: they require a license or an NDA. AES67 is all about transparency.”
AES67 has a number of significant advocates. In fact, the protocol comes out of a collaboration that saw proprietary-network developers and marketers of Ravenna, Dante, QSys, Wheatnet, and Livewire jointly seek common ground and areas of overlap common to their Layer 3 protocols while still using their own particular ways to address other aspects of networking, such as how they format audio data and distribute their sample clocks.
Ultimately, AES67 is meant to let users choose system components from different manufacturers with the expectation that they will be interoperable. However, it’s unlikely that AES67 will offer these Layer 3 formats the same seamless media-distribution standard that AVB seems to promise Layer 2-systems users. For instance, AES67 doesn’t provide device discovery, in which a network tries to find out what other elements are on a network it has been asked to interact with.
AVB puts an emphasis on hardware that has achieved the assurances of a governing body, while AES67 is an academic stab at finding some common ground among the growing range of commercial network offerings. The reality is that hierarchies are already being established by market forces, such as Dante’s growing share of the installed-AV market and Ravenna’s traction in the broadcast market in Europe. Audio networking is a game still too close to call.