The AoIP standards that get everything talking

Audio-over-IP (AoIP) is the practice of sending multichannel data over digital networks. A single Ethernet cable can carry dozens of audio channels and other related information, and multiple devices can be set up in intelligent networks that understand which data goes where.

When these networks came into existence in the early 2000s, each manufacturer started with its own proprietary protocol, and attempted to convince everyone that its version was the best way forward for networking. The most common AoIP protocol in use today is the Dante® system originated by Audinate. Focusrite are among the hundreds of companies worldwide that have adopted Dante with great success.

However, there are a fair number of competing protocols on the market, such as Ravenna, Livewire+, and AVB (Audio-Video Bridging), each with its own supporters. Over the years, some protocols fell by the wayside, but there was no clear winner: a significant number of these AoIP protocols remain in common use around the world.

This has the potential for a lot of trouble if contractors or end users want to mix and match equipment that uses competing protocols. Taken on their own, there's no guarantee that any of these protocols will even understand each other, much less play nicely together.

That's where AES67 and AES70 come in.

AES67: speaking the same audio language

Recognising the likelihood of situations where multiple competing AoIP protocols would have to work together, the Audio Engineering Society1 (AES) set out to develop a sort of 'umbrella' standard for handling AoIP data in a way that would allow different protocols to interconnect. Each manufacturer's protocol could retain its own special features and strengths, while still remain compliant with the new standard which would let it communicate safely and reliably with outside protocols.

The AES67 standard was first published in 2013. It came at a time when, for reasons we've explained, the many conflicting AoIP standards were making life difficult for a lot of audio professionals. With AES67 compliance, the critical details of audio streaming are all handled in a way that everyone understands.

For example, if a Dante network is connected to a Ravenna network (common in broadcast applications), AES67 ensures that the two networks agree on the basics: how many channels of audio are being transmitted; what their sample rates and bit depths are; what size the individual data packets are; which data streams take priority in different situations; and how their clocks are synchronized. Essentially, AES67 makes sure that the data that's perfectly formatted in one network doesn't get garbled by another.

“AES67 makes sure that the data that's perfectly formatted in one network doesn't get garbled by another."

AES70: everything's under control

Making sure the audio isn't corrupted is one thing, but making all the different hardware and software on an AoIP network respond to the same commands and controls is another. A group of companies called the OCA Alliance, where OCA stands for Open Control Architecture, started to work on this problem in 2011, and submitted the results to the AES, which formalized it as the AES70 standard in 2016.

AES70 is an open standard that makes sure certain commands are universally understood, so (for example) a digital control surface on one network can tell a mixer on another to mute a channel; subgroup certain other channels; send back level meter readings; etc. AES70 is flexible in that it doesn't dictate how companies design and build their gear, or even that they implement every command in the standard — only that those commands they do choose to implement will be recognized everywhere on a network.

“AES70 is an open standard that makes sure certain commands are universally understood."

Everybody wins

Who benefits from AES67 and AES70? Everybody, really! Manufacturers don't have to worry about incompatibilities making their products look like they don't work; contractors don't have to worry about gear from a different network messing with their installs; and end users don't even have to think about it — everything just works as it should.

Technically you don't have to use both AES67 and AES70 at the same time, but that's common practice, and every piece of AoIP gear follows both standards to assure safe and reliable inter-operability. If you'd like to learn more, you can start your education with this short technical article from Focusrite Pro:

AES67 & AES70: Working Together For Inter-Operability

For day-to-day work in digital audio, though, this quick summary will be all you need to understand why your 'incompatible' networks are speaking the same language.

Words: Mike Metlay