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AVB – Hello there, paradigm shift

An audio networking landscape hitherto dominated by proprietary technologies is being reshaped in favour of an open standards approach spearheaded by AVB (Audio/Video Bridging). That’s the theory, anyway – but is the industry really on the verge of true interoperability, wonders David Davies?

For once, it does not verge on exaggeration to declare that the old world is dead and gone. Across the pro-audio landscape – in install, live and broadcast – the last decade has been one in which a single-brand orthodoxy has broken down in favour of a mix-and-match approach that seeks to employ the most suitable products for any given application. Simultaneously, the desire to join all these products together has provided the impetus for an era of full networking that transcends traditional point-to-point connection.

Proprietary networking solutions have multiplied in number since the 1990s, but increasingly, the need to guarantee interoperability has led the industry down the path of standardisation with regard to both primary networking components: transportation and control. The ongoing AVB (Audio/Video Bridging) project – spearheaded by the AVnu Alliance – is arguably the most salient example.

The momentum behind AVB may appear to be unstoppable – but not everyone is convinced. For many, the crucial battleground is IP and the ability (or not) to operate on existing networks. AVB rebuffs a pure Layer 3, IP-based approach in favour of the use of Layer 2, which is claimed to host offer multiple additional benefits. Meanwhile, Ravenna – regarded by some as a possible ‘European’ rival to AVB – pursues a Layer 3 approach and, unlike AVB, does not require dedicated switches.

The lengthy roll-call of manufacturers and technology developers to have signed up to the AVnu Alliance underlines the extent to which AVB has provided a focus for those wishing to bring clarity to the networking issue. But witnessing the (to put it mildly) variable level of knowledge about the project among attendees to this year’s ISE Future Trends Summit couldn’t help but prompt a few doubts about whether the message has really got through.

“I’ve been ‘soaking in’ AVB since 2007, and sometimes you need to step back and realise your perception and understanding is not that of the industry at large,” admits Lee Minich, president of Lab X Technologies and marketing work group chair of the AVnu Alliance, in ready acknowledgement of the current gap between progress and understanding.

Indirectly, Minich offers as good a starting point as any for a whistle-stop tour of the latest developments in audio networking, including the latest progress of the AVB project, continuing debate over the IP issue, and a renewed focus on features that may result from increased interoperability.

All for one, one for all?

Whatever the imminent future, existing transportation solutions are not about to disappear. Take, for example, CobraNet, developed by Peak Audio and subsequently acquired by Cirrus Logic. Despite its participation in the AVB-promoting AVnu Alliance, Biamp is one of many manufacturers to be maintaining its commitment to this still-ubiquitous technology: executive vice-president of marketing at Biamp Systems, Graeme Harrison, highlights the use of CobraNet in its Audio and Vocia products, adding that Biamp “intends to continue support [for] CobraNet moving forward”.

It is clear that many manufacturers are planning to continue support for existing protocols while moving towards greater standardisation. Harrison, for example, concedes that “the inherent nature of CobraNet did create frustration due to the limitations around speed; [consequently] Biamp looked to AVB for future development around faster devices.”

Move out into the wider networking landscape and we contemplate a world in which customers have a reduced enthusiasm for one-brand/group solutions; they want to be able to pick and mix products drawn from multiple vendors. The need to guarantee that devices can talk to each other has therefore increased exponentially; an impulse that inevitably leads towards standardisation programmes. The desire to reduce/eliminate licensing costs has also provided momentum behind the AVB project, based as it is on IEEE (Institute of Electrical and Electronics Engineers) standards.

“There will still be a market for legacy proprietary technologies [in the future], but we believe that more and more manufacturers and system designers will embrace the prospects of a sustainable ecosystem with interoperable devices that are guaranteed to talk to each other,” says John McMahon, executive director, digital products of Meyer Sound, which is a Promoter Member of the AVnu Alliance.

So what are the primary benefits of Audio/Video Bridging? ‘Bridging’ is networking speak for Layer 2 packet switching, and it is at this level that the “fundamental improvements” of AVB occur, explains Minich, including “more precise timing (802.1AS), stream reservations and admission control (802.1Qat), and traffic shaping (802.1Qav). However, there is [a] Layer 3 AVB media container for RTP payloads called IEEE 1733 in which Layer 3 traffic could take advantage of the underlying infrastructure improvements. Subgroups within the AVnu Alliance have been formed to define how this Layer 3 traffic will route across multiple subnets of AVB clouds, and ultimately to boundary gateway devices to span engineered WANs.” This project is expected to take approximately 24-36 months.

If a desire for greater interoperability is a given, there is still considerable debate regarding implementation. For example, much of the current debate revolves around the viability of employing existing IP networks. This is the approach taken by Ravenna, the audio transportation technology developed by Lawo group company ALC NetworX that is regarded by some industry observers as a European ‘answer’ to the possibly more US-identified AVB. As a pure Layer 3 solution routed via IP, Ravenna – which counts Genelec, Merging Technologies, Innovason and Neumann among its partners – can be added to most existing network infrastructures.

Significantly, the Layer 2-revolving AVB requires the specification of dedicated switches – not the case with Ravenna, which can potentially operate on any manageable network infrastructure supporting multicast and Layer 3 protocols. The extent to which the two approaches will compete is debatable: for now, Ravenna is focused towards broadcast applications, while AVB has greater resonance with live touring and other areas of fixed install.

ALC NetworX senior product manager Andreas Hildebrand confirms that a pure IP/Layer 3-based approach requires more administrative and management support of the network infrastructure – a necessity that is likely to be particularly problematic for live sound. Accordingly, it could be that – as Hildebrand suggests – “AVB will have its natural place in applications where insertion of a new network infrastructure is feasible and content distribution can be limited to a LAN segment, while Ravenna will be the preferred technology for larger, already installed corporate-type networks spreading across several subnets.”

Merging Technologies is among those for whom Ravenna currently “ticks all the right boxes to serve our customers’ requirements, be they in broadcast, recording, live or fixed installations,” says Merging’s Claude Cellier. “We will, of course, continue to support existing protocols, and the best testimony to that is that our first hardware-based product with Ravenna support, Horus, is actually able to serve as a ‘bridge’ between these two worlds.”

Meanwhile, the overall audio-over-IP ‘movement’ is being complemented by an Audio Engineering Society project, X-192, which – in the words of its mission statement – seeks the creation of ‘a high performance streaming audio-over-IP interoperability’ standard. X-192’s supporters include QSC, which backs interoperability of products over Layer 3 networks and is the company behind the Q-Sys integrated system platform. Featuring Q-LAN – a standards-based, low-latency Gigabit Ethernet network implementation – the non-AVB-compatible Q-Sys reflects a desire “to base our products upon industry standards from much larger industries than the professional audio industry,” says Rich Zwiebel, QSC Audio’s vice-president, systems strategy.


Hildebrand reveals that ALC NetworX and Ravenna partners are participating in several SDO bodies. Meanwhile, the standardisation process for AVB is now entering its final stages. All IEEE AVB standards are complete, with the exception of 1722.1, which determines discovery, enumeration, connection and control. This is expected to go to sponsor ballot in April, reveals Minich, and should be an official standard by Q3.

There has also been recent progress regarding AVB device certification, with recent weeks bringing news of a link-up between the AVnu Alliance and independent test house UNH-IOL. Certification testing will begin this August, while pro-audio product assessment will commence in Q1/2013. Alliance members Avid, Biamp, Extreme Networks, Harman, Meyer Sound and Riedel are among those expected to submit devices for certification in the first wave – although no specific product details have been released as yet.

Meanwhile, there are plenty of relevant solutions making their way into the market. Take Biamp, whose AVB-based Tesira scalable media system for digital networking is due to ship on 14 May and delivers a spec including: modular scalable I/Os, DSPs and networked end-points; up to eight DSP cards in a single chassis; and a maximum of 420 x 420 digital audio channels.

Meyer Sound is among the others stepping up to the plate, with its engineering team working on the implementation of AVB in multiple new products, including the D-Mitri digital audio platform and CAL column array loudspeakers.

…with differentiation

If, for many, AVB is likely to provide the basis of future networking strategy, individual vendors will be obliged to rethink how they go about ensuring a commercial edge hitherto drawn – in part at least – from proprietary protocols. It seems inevitable, therefore, that the focus will gradually shift towards talk of additional functionality.

In this regard, Dante – the audio networking solution developed by Australian company Audinate that offers support for AVB and is regarded by many as a pathway into the AVB world – appears to be in a strong position, with adoption by more than 50 OEM manufacturers to its credit. Invited to detail the advantages of what one might term Dante AVB over its ‘standard’ equivalent, Audinate co-founder and current COO, David Myers, explains: “Dante is by design a complete networking solution – not just a set of protocols like ‘standard AVB’. Audinate’s customers use Dante because they get all the required audio networking components (sync, transport, plug & play operation, latency management, label-based routing), as well as a comprehensive set of solutions and products which augment the basic audio networking functionality, such as: PC interfacing with Dante Virtual Soundcard, very high performance with the PCIe card, glitch-free redundancy, support for routed IP networks (Netspander), network configuration and monitoring tools, etc.”

Certainly, Dante’s ability to employ both AVB and non-AVB switches seems destined to stand it in good stead as the outlook continues to evolve – not least with regard to the increased role of IT personnel in devising and managing complex networks. “Often, these managers will be influential in making the switch selection, and not the AV installation contractor,” predicts Myers. “Off-the-shelf switch availability from the leading enterprise switch vendors of AVB-compliant switches will be essential to widespread adoption for media networking. […] There are a couple of switches available and more should be over time, but it will be important to be able to buy switches from any of the IT manager’s preferred switch suppliers.”

In terms of the products that sit on the network, the new era of interoperability should allow specifiers much greater freedom to select the best products for any given application. Allen & Heath R&D director Rob Clark, for example, is hopeful that manufacturers will be able to devote time “previously spent supporting multiple interface standards on differentiating their products with exciting new features, in what is already shaping up to be a highly competitive market for networked audio.”

Simultaneously, there will be a further challenge in the integration of audio, video and command and control in more elaborate deployments. Jürgen Scheuring from software think tank UMAN points out: “With the advent of an AVB-enabled backbone that is shared by all parties, the integration of such complex scenarios will be tough to handle for each manufacturer on his own. [But] rather than this being a problem, it could represent a huge opportunity. If manufacturers make a step towards becoming system providers rather than simply device manufacturers, they could expand their business to incorporate this new infrastructure.”

The knowledge deficit

The control aspect of the networking puzzle has arguably been rather under-served by industry discussion of late – but here too, things are now moving rapidly. In particular, the OCA Alliance’s pursuit of an open control standard may dovetail neatly with the transportation philosophy of AVB [see Box for more].

Meanwhile, momentum behind the latter continues apace, with Minich and McMahon among its many articulate advocates. But the aforementioned Future Trends session underlined that there is still a considerable knowledge gap about the benefits of AVB on the part of installers and end-users. “Within the [AVnu] Alliance, we have realised this oversight and are embarking on a very concerted effort to elevate the understanding of the technology,” says Minich.

The complexity of the issues outlined in this necessarily brief overview is such that many could be forgiven for swerving the networking issue altogether until the lay of the land becomes clearer. Alas, overcoming such confusion and reticence is essential if a meaningful vision of an interoperable future is to be realised any time soon.

Questions of control

The control landscape has historically been dominated by manufacturer-specific innovations. But here, too, there is now enhanced focus on standardisation, exemplified by the activities of the Open Control Architecture (OCA) Alliance.

Established by nine pro-audio manufacturers, the Alliance is pursuing the elevation of OCA to the status of an open public communications standard for the control and monitoring of devices in professional media networks. In itself, OCA does not provide signal transport, but is designed to cooperate with current and future transport standards, including the AVB suite.

The starting point for OCA was AES-24, a system control protocol developed by the AES in the 1990s. But according to Ethan Wetzell – platform strategist at OCA Alliance member Bosch Communications Systems – this foundation has been transcended thanks to “extensive modifications, enhancements and extensions… OCA has come into its own and really is a unique architecture.”

OCA is already informing some major product developments – not least Bosch’s own OMNEO architecture. Combining a transport suite employing Dante with an OCA-based control component, OMNEO encompasses both primary concerns of a media network.

According to Wetzell, “interest in, and enthusiasm for, OMNEO has been very high from all areas of the industry.”