Technology: Campus-wide audio networks
Technology: Campus-wide audio networks
AoIP networking offers flexible and cost-effective interconnections within a HOW infrastructure. Frank Wells covers the considerations
Audio over IP (AoIP), the distribution of digital audio over an internet protocol network, offers benefits that include lossless transmission from device to device and location to location, reduced cabling costs, multichannel audio over a single interconnection and bidirectionality – the ability to retrieve and insert signals from any location in the system. Building a complete facility-wide, or even campus-wide in the case of larger houses of worship, system leverages these benefits to offer audio system flexibility that is impractical in the analogue domain.
For instance, with a networked audio system, an audio mix from a main sanctuary can be tapped off the network for playback in a youth room or multi-purpose room for an overflow audience. Similarly, audio could be sourced from that youth room to share in the sanctuary. A worship service mix can be easily tapped for a nursery area, cry room or in hallways. A music playlist could be substituted for the worship service for ambient mood setting.
In an analogue system, such capabilities would require cabling – often heavy, expensive and bulky multi-pair cables – to be run to each location, typically from a central location where a hardware patchbay or an expensive router would be required to flexibly distribute signals. Such flexibility was rarely implemented even in large, well-funded HOWs.
A few words on wire
AoIP digital audio networks are fundamentally specialised applications of commonly available Ethernet technologies. Anyone who has connected a computer to a hardwired network is familiar with the cabling and connectors – a relatively small diameter cable that internally has four twisted pairs of wires terminated in an RJ45 connector. Such cabling is referred to by a category nomenclature that refers to specifications for the performance-determining internal construction of the cabling.
For digital audio, Cat-5e would be the minimum acceptable cable type. To achieve gigabit data speeds over longer distances, Cat-6 provides an upgrade and Cat-6a and Cat-7 offer further improvements in performance. Regardless of the cable type chosen, the overall distance limit for a single cable run is 100m. Cat-6 cabling is not significantly more expensive than Cat-5e and is recommended for installed wiring (room-to-room) though, if budget allows, where video networking may also be desirable, where distances are beyond half the limit and for future-proofing the installation, Cat-6a or Cat-7 could be an option. For most applications, the more flexible Cat-5e cabling can be used for short, local connections.
For distances longer than 100m, as in a large HOW or one with separate buildings, AoIP signals can be converted to optical fibre and run for maximum distances measured in kilometres instead of metres. Fibre is more expensive and requires specialist knowledge to terminate.
In general, a single run of cabling is all that is needed for a connection at any point in the network, though in a new installation or system-wide network, running a second cable for redundancy (or for further future-proofing) is recommended.
The components of an AoIP networked audio system are relatively straightforward. Bookending the system are transducers and acoustic/electrical signal conversion – microphones and guitar pickups on one end and amplifiers powering loudspeakers on the other. A network-capable audio interface reformats either analogue or already digitised audio into a network-compatible stream. Output as an Ethernet-compatible signal, the AoIP formatted signal is plugged into an Ethernet switch – in simple terms, a box with a bunch of RJ45 connections that allows multiple devices to be connected to a network. A downstream device that speaks the same AoIP language is also connected to the switch so it can retrieve the desired signals from the data stream and send them along to additional system devices.
The switch is the moderator of the system dialogue, interleaving packets of digital data (audio samples in the case of AoIP) with accompanying data and timing information that allows other devices on the network to retrieve individual or groups of channels from, and to insert additional channels into, the network stream.
Networked audio can be visualised as fleets of vehicles on an enormous traffic circle. Picture each source as having its audio samples deployed into identically coloured cargo vans. A main programme two-channel mix might all be assigned to a fleet of white vans, each vehicle in the fleet (the digital data packets in network speak) sequentially loading up as many audio samples as it can hold, posting a sign on its side saying what’s inside and what its place was in line, and then starting off into the flow of the traffic circle. Within the traffic circle, the vans may merge into traffic with a multitude of other differently coloured vans (packets of data from other audio streams), each with their own unique signs saying what they are carrying and identifying their position within their own fleet. Around the traffic circle, exits let fleets head towards a particular destination and incoming lanes allow new fleets to join the traffic in the circle. Wherever along the highway the two-mix needs to go, the white van fleet exits, reassembles in the proper order and their cargo is sequentially offloaded. The cargo vans are a bit magic in that they can leave the circle at any and all exits simultaneously.
Each location being connected to an AoIP network should have its own home run of cabling between the location and the switch. At a given location, if multiple networked devices need to be attached, a local switch can be used for additional interconnectivity.
High-quality switches are important in AoIP applications. Switches must be able to support simultaneous gigabit data transfer and, to prevent audio connection interruptions, have the ability to turn off power-saving features. End-users should investigate the requirements specified for the networking protocol they plan to implement.
Wait, there’s more than one protocol?
Professional audio (and video) are beneficiaries of the highly standardised IT industry as AV systems can adopt IT infrastructure such as Ethernet communication protocols, cabling and switches. But when it comes to using that infrastructure for audio, pro audio manufacturers have to choose between competing standards, or might even have developed their own proprietary protocol. This creates a language barrier to communication between devices. Examples of the options include Audinate’s Dante – certainly the most ubiquitous AoIP protocol; the USA’s earliest AoIP protocol, Livewire, by the Telos Alliance, found in widespread broadcast use; the Ravenna protocol from Lawo subsidiary, ALC NetworX, also with wide (if European-centric) adoption for broadcast and music production applications; and QSC’s proprietary Q-Sys integrated audio, video and control platform.
It’s up to the end-user to ensure that the networked hardware they want to use is compatible. Fortunately, there’s a digital Rosetta Stone available that allows disparate audio networks to share audio data. The Audio Engineering Society created its AES67 AoIP interoperability standard for audio transport with the specific goal of shared access to audio signals across compliant networks. Although there are some qualifications, the audio networking protocols above were specifically mentioned here because they are examples of AES67-compliant networks that can share audio information. There are rapidly increasing numbers of hybrid systems in use where audio sharing across gear brands and AoIP protocols is facilitated by AES67 compliance.
In every category of professional audio gear, there are now network-capable options, including microphones with network outputs and powered loudspeakers with network inputs. Digital audio consoles now commonly have network ports either natively or via option cards. For devices without native networking capability, there are network-equipped interfaces that offer the necessary conversion for mic-level and line-level analogue input, for analogue output and for digital I/O. ‘Soft’ interfaces allow computer Ethernet ports to be used for digital audio network connections for digital audio workstation and other uses.
While audio networks for production applications are expected to remain independent for at least the immediate future, IP-based networking of audio and video mixed media is of immediate interest for HOWs that wish to move both video and audio within their facilities and campuses. There are a few non-proprietary protocols leading the competition for adoption. AVB (Audio Video Bridging, developed by the IEEE standards organisation) has been embraced by a number of audio manufacturers, but its adoption has been slow overall (at least in part because of the pace of development of the specialised switches required). Making a fast entry into the marketplace, particularly in broadcast, is the new SMPTE 2110 suite of standards for professional media over IP. AES67 audio transport is written into SMPTE 2110, while a conversion device is necessary to merge AES67 audio into an AVB network.
For audio and video distribution, the NDI standard (developed by NewTek and made available with royalty-free licensing) is an audio/video IP network option adopted by a large number of manufacturers. NDI can function on existing gigabit networks and can be used on wireless networks for some applications. At least one developer of NDI-equipped tools has announced an AES67-NDI interface.
Audinate has also entered the competition, announcing a partnership with the SDVoE (Software Defined Video over Ethernet) Alliance for an integrated AV control platform (for more details, see ‘The future of audio networking’ in WAVL, Nov/Dec 2018).
Where to start
Begin conceptualising a HOW AoIP system by asking questions. What protocols are supported by your digital audio console of choice? How about by your processing and amplification chain? Can your loudspeaker system accommodate networked audio inputs? Where do you need audio signals now and where do you source them from? Where might you like or need networked audio connections in the future?
Make a needs list and a wish list. The wiring is cheap – while you are making runs elsewhere within your facility, run Ethernet cabling to locations you may wish to use in the future, even if you leave those leads unterminated in the short term.
It’s not often that the simpler choice yields more sophisticated results with reduced expense. IP-based system interconnection offers such a choice.
This article first appeared in the January-February 2019 edition of Worship AVL. Subscribe at www.proavl-central.com/subscribe/worship.