Networked Audio: One Token Ring to Rule Them All
By: Krystofer von Hybschmann, MCH Senior Media Systems Consultant
Analog was the standard for audio for a very long time. However, analog audio signals are susceptible to electromagnetic interference, voltage drop, and high-frequency attenuation over long cable runs. As we were all connecting to the World Wide Web through AOL or CompuServe at home, audio engineers were developing a new Audio over Ethernet (AoE) to mitigate these issues, especially for airports, stadiums, convention centers, and theme parks where cable runs can be long.
CobraNet was a First-Gen, Layer-2, AoE, which became one of the most heavily-adapted, proprietary protocols, until about 2006. CobraNet had its share of limitations. For example, it could not traverse routers and therefore could not be on Wi-Fi, was limited to 100 Mbit/s, and had a minimum of 1.33 milliseconds buffering delay in the audio transmission.
In 2006, Audinate developed Dante, a new type of AoE using a philosophy that there are three pillars tofnetwork audio: a complete set of tools, development and support, and a broad range of products. Dante could traverse routers (Layer-3), had Quality of Service (QoS) settings, and used Real-Time Transport Protocol (RTP) and Precision Time Protocol (PTP). Like other Second-Gen Layer-3 protocols that followed (including Q-LAN, Ravenna, Livewire+, and WheatNet-IP), it had addressed the limitations of its First-Gen predecessors, like CobraNet and EtherSound.
Shortly thereafter, in 2009, the Audio Engineering Society (AES) began developing an AoE standard protocol for networked audio. This standard primarily provided interoperability among Layer-3 networked solutions, like those listed above, and soon after included interoperability with the Layer-2 IEEE standard known as AVB (Milan), which uses Time-Sensitive Networking (TSN) instead of PTP or RTP. In 2013, the AES67 standard was published, which aligned with many of the Layer-3 Protocols listed above, also uses PTP, and accommodates speeds up to 10Gbit/s through routers and over the Internet.
Without the interoperability of AES67, system designers would have to pair, for example, Dante-enabled devices with Dante-enabled devices, to ensure the AoE gets from its source to its intended destination(s). Because of AES67 interoperability, Dante-enabled devices can stream audio to/from QSC’s Q-LAN devices as well as some devices under the Avnu Alliance’s AVB protocol, allowing for more flexible planning for the designer and end-user.
First-Gen AoE was created to overcome signal loss and degradation over long analog cable runs.
Second-Gen AoE addressed latency and expanded cable run distances.
AES67 allowed individual protocols (or network audio solutions) to interact with equipment of other manufacturers.
This flexibility has allowed system designers to leverage facility network infrastructure or a structured cabling plant instead of pulling separate cables or utilizing facility Wi-Fi infrastructure to pass audio throughout a facility. Also, AES67 allows for huge, highly-sophisticated sound systems like the one serving in The Stadium Tour in 2022 with Def Leppard, Mötley Crüe, Poison, and Joan Jett & the Blackhearts. The system used a fraction of the cables that a traditional analog system would have used. It was easier to deploy, set up, manage, and potentially offered some cost savings. Deploying an AES67-aligned system into a courthouse, emergency operations center, university, or other project-types reaps similar benefits. Central processing and routing, which include the use of (commonly called) break-in or break-out boxes, allow for connecting microphones, loudspeakers or recorders, and even include USB interfaces for laptops and PCs.
Layer-2 Protocols like CobraNet, EtherSound, and AVB (Milan) are limited to network switches and are unable to traverse routers without converting from digital to analog and back again. Layer-3 Protocols like Dante, AES67, Q-LAN, Ravenna, Livewire+, and WheatNet-IP can traverse routers and even the Internet. While analog still has its place in simpler AV systems, current Layer-3 AoE is the best available transport for audio, offering faster speeds, lower latency, PTP clock synchronization, and QoS priorities for media traffic. With continuing network advances, specifications, and protocols like SMPTE ST 2110 which evolved AES67 capabilities and provided the bandwidth to include video, AV systems have the potential to be single-cable solutions. This may be a lofty goal, but when properly designed, programmed, and deployed, an AES67-aligned system is unstoppable.