An AoIP Primer I

Dante, AVB/TSN, Ravenna, AES67. Perhaps you've heard of one or more of these terms. What are they? What do they mean/do?

AoIP (Audio over Internet Protocol) is a category of systems that take digitized audio and allow you to send to another network device in a point-to-point manner in realtime. It's a little like sending an email, but instead of text you're sending audio streaming in realtime. As your average Gigabit network can move things around pretty quickly, it's simple to send many tracks of audio at once in realtime.

Great. Why would I want to do this?

Well for starters, imagine setting up a simple network between two different DAW stations in adjacent rooms. Instead of running multiple snakes or dozens of cables connecting mixers and interfaces, you can just send audio over the network with a single Ethernet cable. In most cases, existing infrastructure is sufficient, though in some cases a managed Ethernet switch may be necessary. A managed switch allows access to QoS (Quality of Service) parameters which sets transmission priorities for different types of data packets. In some cases, we need to raise the priority of AiOP packets to prevent bottlenecks and keep the audio info moving reliably.

A few sentences back I called AoIP a category of systems. The reason for that is that AoIP is a concept and not a specificf protocol. All the different protocols we're going to look at today are examples of AoIP. They'll have a lot of similarities, but are in effect competing protocols. Some are better at this or that, but in the end they serve the same main function. i.e. shuttling audio around a network so that people can tap in to, monitor, or process it.

Of the different protocols, Dante is probably the most well known. Created by Audinate, and currently boasting support from over 600 manufacturers and more than 4000 different products, the Dante protocol is widely used.

AVB/TSN (Audio Video Bridging/Time-Sensitive Networking commonly just called AVB) is similar in many ways to Dante, but it is open-source and not proprietary. That means as a manufacturer you needn't pay a licensing royalty to anyone to incorporate it into your product. AVB is gaining some momentum but isn't quite as widely used in practice as Dante. AVB also requires use of an AVB-certifies network switch whereas Dante can run on existing infrastructure so long as it has sufficient bandwidth.

Ravenna is also open-source and available to any manufacturer. Typically used in the Broadcast industry more than live sound, it is much more flexible in many respects but also can be more confusing to setup and maintain. Ravenna is based around AES67 protocols which we'll discuss next.

AES67 is a standard that was proposed in 2013 by the Audio Engineering Society as a means of bridging various digital network protocols to maximise interoperability.

Many digital mixers and higher-end interfaces that have an option for expansion cards may have any one of the above or more available to bring that function to the device. Others may come with one of these protocols as standard.

So how might any of these be useful exactly? Well, in the brief example above with two studios in adjacent rooms, imagine having a live drum room in one studio, but they need to be recorded in the adjacent studio?. After all the mics are placed and input to the board, if it has an AoIP connection, you can route the signals back out of the board, into your Ethernet port so that the adjacent studio can access the signals as inputs and route accordingly to whatever device they like. The interfaces take care of all the timing information for transmission and reception and any latency is automatically read on the other end and the DAW can accurately account for any latency compensation keeping everything in perfect sync.

At this point, it really doesn't matter where the receiving DAW computer is. It could just as easily be anywhere in the world. We had a client a couple of years ago that bought two different rigs. One housed at a club, and the other at a studio across the city. In order to make it all work we needed to incorporate a device on either end that had a GPS unit built in allowing the GPS system to offer sample-accurate timing because of the distance. Impressive.

AoIP really offers a lot in convenience, less cabling, highly flexible routing, low latency and more.

We'll be continuing this series in the future looking at specific examples of usage.