Setting the standard

Can AVB really be the plug-and-play solution to revolutionise audio and video networking? Mel Lambert talks to the major players of the AVnu Alliance to find out

Connectivity is the key to the successful networking of live production systems. Until recently, the ability to pass digitised audio and video signals across high-speed network topologies that provide time-synchronised, low-latency delivery of multichannel audio, HD digital video and bidirectional control signals has been problematic.

But the development by The Institute of Electrical and Electronics Engineers (IEEE) of various open-standard – or non-proprietary – schemes that ensure consistent, on-time delivery of high-data bitstreams across large-scale Ethernet-based networks is providing exciting new opportunities for a growing number of manufacturers. Allied with the promotional activities of AVnu Alliance, which was formed last year to support the new IEEE-devised implementation, Audio Video Bridging - or AVB - gives every appearance of being the plug-and-play, vendor-independent solution for which the international live-performance industry has been searching.

Established just a year ago, coincidentally at the time of InfoCOMM 2009, AVnu Alliance is an industry forum dedicated to promoting the adoption of the Audio Video Bridging standards for professional A/V, automotive and consumer applications. Founders include Broadcom, Cisco Systems, Harman International, Intel, Samsung Electronics and Xilinx.

Lead membership included a number of prominent companies from the pro-audio community - notably Meyer Sound and Avid - together with several chip manufacturers, including Marvell, Micrel and Analog Devices, plus the engineering design firm Lab X Technologies. Recent new members include Barco, Pelagicore and Shure, in addition to Audinate, Sennheiser, UMAN (Universal Media Access Networks) and University of New Hampshire Interoperability Lab, a third-party centre for testing data-networking technologies.

‘AVnu Alliance’s intention is to advance the quality of experience for networked audio and video, and establish a professional quality A/V experience in networked environments, for music studios, concert halls, stadiums and similar applications,’ considers Rick Kreifeldt, the organisation’s chairman, and vice president, systems architect at Harman International. Prior to AVB, ‘out-of-sync audio and video, glitches and delays could occur in many of these settings, unless complex, proprietary solutions are deployed,’ Mr Kreifeldt continues. ‘To address these issues, AVnu Alliance is promoting IEEE standards.’

AVB is designed to work over widely-used IEEE 802 layer 2 networks that provide connectivity features for tightly controlled media stream synchronisation, buffering and reservation. AVB enables higher layer protocols and applications to provide professional-quality A/V transfers even if there are various lower-layer network links in the path between end-point devices.

Because IEEE 802.1 Audio Video Bridging, and its related IEEE 1722 and IEEE 1733 standards, define various networking link-layers that encompass system control data and digital bitstreams, AVB is seen as a one-stop solution available via single Cat5/6 connections. ‘Our industry is too small to support proprietary networking solutions,’ considers John McMahon, Meyer Sound’s executive director of digital products. ‘By leveraging the ubiquity of mainstream Ethernet, we have access to an open, non-proprietary standard that benefits both end users and hardware manufacturers. With silicon makers as part of AVnu Alliance, we are assured that AVB will be both inexpensive to implement and accessible at all levels of the professional A/V industry. In turn, AVnu Alliance will ensure interoperability of AVB-enabled devices.’

‘Existing networking schemes do not incorporate timing data,’ says Robert Boatright, director of research of Harman International’s corporate technology group. ‘With AVB, each data packet is time-stamped by each input port. This [synchronisation] information follows the digitised A/V material through each network to its assigned delivery point,’ where the sample-accurate timing data ensures low latency and accurately synchronised playback. Since AVB can reserve up to 75 per cent of the network capacity for audio and video bitstreams, with remaining unreserved capacity being available for data, a separate data network is not required. Soon-to-be-implemented 10Gbit Ethernet AVB will enable end users to develop reliable networks with data bandwidth necessary to handle on-demand multichannel audio channels, HD video signals and complex control data.

According to Mr Boatright: ‘Our dbx SC 32 and SC 64 Digital Matrix Processors already feature AVB connectivity, as do the soon-to-be released co-branded BSS/NetGear Ethernet switches. A PIP-USP4 add-on module for our Crown CTS Series power amplifiers adds AVB connectivity, via a simple upgrade. Harman is actively developing products across all of our divisions.’

AVnu Alliance recently hosted its second plug fest to check product-to-product compatibility via AVB-compliant networks. ‘Alliance member plug fests are the key to moving AVB technology from paper to practice,’ Mr Kreifeldt considers. ‘By implementing compliance test procedures to ensure A/V devices work together, we continue our collaboration with member organisations to refine interoperability specifications and enhance the network backbone,’ and hence provide reliable, low-latency and high-resolution connections. Such forums are expected to be held several times during the coming year.

Although implementation of AVB-compliant networks will require suitably-equipped Ethernet switches and bridges, many of the currently available models already offer built-in AVB capability, which can be implemented via a simple firmware upgrade. AVB will also co-exist with other transfer protocols, including CobraNet, EtherSound, Audinate Dante, AES50 and Q-LAN, albeit without integral sample-accurate synchronisation. ‘This will enable AVB users to continue using legacy products within a mixed network environment,’ Mr McMahon stresses, ‘although AVB obviously offers more capabilities than older generation networking topologies.’

‘AVnu has a defined market focus, with the mission to meet the needs of our core markets,’ Mr Kreifeldt reflects. ‘Whereas the standard itself by necessity must be fairly broad, within the Alliance we are specifying critical performance metrics that meet the needs of the customers in these markets.  Developed by the networking community, AVB’s openness has already led to the announcements of AVB silicon. Previous niche technologies did not offer the same large market potential; AVB extends the performance for professional A/V and is cost-effective for large-scale use.’

‘Since our inception, Audinate has used standards to develop a complete IP-based media networking solution,’ states the firm’s COO, David Myers. ‘AVnu Alliance’s goal for promoting interoperability and openness among A/V equipment vendors across the industry will give customers greater flexibility in implementing networked systems.’

At the recent CES Convention in Las Vegas, chipmaker Broadcom organised a demonstration spotlighting the use of Audio/Video Bridging in a real-world application. Digitised audio was sent from a dbx SC 32 digital processor through two BSS/NetGear AVB-compliant Ethernet switches to a pair of Crown CTS600 power amplifiers; Harman Professional’s System Architect and HiQnet command protocol handled system configuration and control. Broadcom’s Hawkeye 53314 ICs provided AVB interfacing and the generation of timing reference signals to ensure low-latency, on demand delivery of multichannel digital audio. Despite a dramatic difference in Ethernet path lengths and switcher port connections, the source signal arrived in perfect synchronism at the two playback devices, courtesy of AVB’s time stamping and guaranteed bandwidth from source to destination via an AVB-compliant network.

Also in development are extensions of various IEEE standards that will provide plug-and-play interoperability between AVB-compliant systems from different vendors. The in-development IEEE 1772.1 standard will provide automatic discovery, enunciation and communications across AVB networks. ‘The idea is that AVB-compliant components on the network will advertise who they are,’ Mr Boatright points out, ‘and enumerate what they are capable of delivering’ to other components in terms of, for example, sample rates and bit depths of digitised bitstreams. ‘Then, if the subsystems are deemed compatible [by the controlling system-command program], they will be able to communicate with one another.’ This extension is based on experience from the Internet Engineering Task Force (IETF) Zeroconf Working Group.

At Avid, the ability for Venue live-performance digital consoles to directly communicate with and control microphone pre-amplifi ers, processors and amplifi ers/powered speakers via AVB offers some exciting possibilities. ‘Yes, our initial focus for AVB connectivity will be centred around our livesound products,’ agrees David Gibbons, general manager at Avid Live Systems. ‘We expect to have practical technology demonstrations later this year. Audio networks are very attractive in live applications, because they are flexible, easy to connect and enable multi-zone operation.’

‘The first phase for us will be to increase our connectivity options for the way in which Avid mixing consoles, stage boxes and other components will communicate with one another to ensure multichannel audio transfers via Cat5,’ he continues. ‘That longstanding industry wish list of how to accomplish low latency, high channel count and clock recovery over a Cat5 network has been solved with AVB; the technology offers high reliability and tight audio clock synchronisation with less than 2ms latency across a seven-hop 100Mbit Ethernet network, for example. Even lower latencies are possible using Gbit Ethernet.’

‘We will then concentrate on the second phase, which will involve monitoring the flow of data around larger systems,’ says Mr Gibbons. ‘This might include gathering information from a wider network of consoles, amplifiers and loudspeaker controllers located across multiple system zones, including FOH, stage monitors, lobby areas and so on. That capability will provide essential fault monitoring and recovery, [which] will ensure fully reliable operation and better confidence for the operator. Then the third phase will be to implement network-wide remote control across a multi-zone AVB-compliant network, allowing you to actually reconfigure and control remote devices from within the console.’

‘Existing, non-timed networks lack the robust, plug-and-play networked connectivity needed for complex production environments,’ offers Rob Silfvast, Avid’s principal system architect for Live Systems. ‘AVnu Alliance is being driven by companies that are relevant in the industry and provides regular contact between these organisations in a cooperative forum.’

‘The work that has begun within [AVnu Alliance] is critical as manufacturers embrace and deploy AVB,’ states Colin Duggan, Analog Devices’ product line director, CPT/DSP. ‘As a provider of flexible and innovative semiconductor solutions, we believe that AVB can contribute much to this organisation in an effort to make the user’s experience seamless across all markets and applications.’

Meyer Sound already offers full AVB connectivity with its D-Mitri Gbit network-based digital audio processing and distribution platform, which provides multichannel audio processing, signal distribution, I/O devices and control software. ‘We expect to see full connectivity between D-Mitri and other products from AVB supporters by the end of 2011,’ Mr McMahon predicts. ‘[AVnu Alliance members] Xilinx, Intel, Broadcom, Cisco and Lab X are developing AVB-compliable chip sets, routers and/or firmware that will streamline the development of networked audio/video systems. Of course, their commercial motivation is likely towards the far larger automotive and home-entertainment markets,’ where costs can be amortised over millions rather than thousands of installations. ‘But our industry will benefit from access to these building blocks at lower costs than if they were innovated just for us; it’s a very productive and cost-advantage environment for the pro A/V market.’

And the addition to AVnu Alliance’s membership of Sennheiser and Shure, both of whom manufacture a range of wired and wireless microphone systems and IEMs, means that live-sound system operators can accommodate AVB-compliant signals at the sound source. ‘Sennheiser manufactures the ‘terminal’ units in the audio chain - microphones, headphones and loudspeakers,’ points out Enno Grotelüschen, the firm’s director of development, information systems. ‘We need to make sure that interfaces on our microphone products’ – including Sennheiser wireless microphones and Neumann digital models – ‘match the market standards. We expect that AVB will become a very important open standard in the marketplace, and will first assert itself in the installed sound segment. What is most important about AVB is that users will not have to go into the depths of network administration to get their audio or video from A to B; from the source to the recipient.’

The continuing series of plug fests organised by AVnu Alliance will enable vendors to check full compatibility with a growing number of AVB-compliant systems. ‘We predict that customers will actively look for the AVnu Alliance logo on component products,’ Mr McMahon offers. ‘Licensed use of that logo on AVnu Compliant products - and its implied full compatibility with AVB standards - will guarantee plug-and-play operability for our customers.’

As will soon be realised, AVnu Alliance is playing a critical role in the industry-wide adoption of the Audio Video Bridging network standard. ‘The IEEE does not provide compliance or interoperability testing for any of its work,’ Mr Kreifeldt explains. ‘Instead, it leaves that to industry organisations. AVnu will continue to develop various compliance-test procedures and processes that will ensure full AVB interoperability of networked A/V devices – including regular plug fests - thereby providing the highest quality, most reliable streaming experience.’

‘The Alliance is actively forming a very broad and strong member base from professional audio and video manufacturers. Our eventual goal for membership would include all A/V manufacturers interested in deploying interoperable and compliant AVB products,’ states Lee Minich, chairman of AVnu Alliance’s Marketing Work Group, and president of Promoter Member Lab X Technologies.

www.avnu.org