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Blending The New With The Tried And True



Calrec Audio has long recognized the potential for AVB—the professional-quality streaming standard for networked audio and video content based on the IEEE 802.1 Audio Video Bridging standards—to address Ethernet’s most serious shortcomings as a transport for streaming audio. To underscore that belief, Calrec joined the AVnu Alliance earlier this year so that we could not only learn from others who advocated for AVB, but also use our wealth of expertise in audio networking to help shape the new protocol. Ultimately, Calrec wants to make sure the needs of audio professionals are well-represented in the new protocol. Now, as part of our commitment to advancing the AVB standard, Calrec has adopted AVB into our Hydra2 audio routing system, adding a new and important layer of versatility to the system.

Hydra2 is the audio networking fabric that is used to move signals wherever they need to go—from audio interface circuits (such as microphone preamps, AES3, MADI, or SDI) to console DSP frames, or between consoles. Hydra2 is extremely flexible and highly reliable, with a huge capacity and redundant hardware that automatically deploys in the event of failure.

Given such a robust networking architecture, it was an obvious choice to connect an AVB interface directly to our Hydra2 network. To understand why, it’s important to know that Hydra2 was originally conceived as a means to network Calrec consoles and audio interfaces only. In order to meet the requirements for live broadcasting (including high capacity at extremely low latency) and to add a great many other broadcast-orientated features such as access management, Calrec had to implement a proprietary design.

What’s more, the design was built for deterministic behavior, which is not inherent in standard Ethernet. The proprietary nature of the network means that it can connect only Calrec equipment. This is where AVB comes in.

Integrating the AVB interface means that incoming AVB channels, once they are converted into the Hydra2 format within the AVB interface circuitry, will always be available to the entire Hydra2 network. Any or all Hydra2-networked consoles can have equal access to these audio signals. Also, it is possible to route signals from the AVB interface across the Hydra2 network directly to other audio interfaces, which allows the network to act as a signal distribution and routing infrastructure, and as a means of translating AVB channels into other audio formats for distribution to non-AVB equipment. Similarly, with outgoing AVB audio, all consoles and interfaces on the Hydra2 network can access and contribute to outgoing AVB streams.

Adding the AVB interface provides a connection to our proprietary network, in effect overcoming the limitations of proprietary technology. One can use Hydra2 to connect the Calrec consoles and infrastructure for low-latency, utterly reliable and deterministic high-capacity routing, and then rely on points of contact with an AVB network to import and export other signals easily.

For example, a Hydra2-AVB integration might be useful with a communications system such as Riedel’s Artist system. In a live studio facility, it is common for large numbers of signals to pass between the communications system and the audio mixing console. AVB provides an affordable, flexible way to make it happen. (In fact, Riedel and Calrec have tested connecting Hydra2 and the Artist intercom system over AVB, with excellent results.) Similarly, if a video routing system, equipped with audio de-embedding capability, were to have an AVB connection onto a Hydra2 network, it would provide an excellent mechanism for getting those de-embedded signals in and out of the audio mixing console domain.

The examples above demonstrate the ability to make high-bandwidth, flexible connections between different subsystems within a broadcast facility. Without a Hydra2-AVB networking architecture, facilities must use somewhat more expensive and inflexible analog, AES3, or MADI connections to accomplish the same thing. The AVB solution, on the other hand, requires only a single installation and minimal cabling (hundreds of signals can be transported on a single Gigabit AVB cable). An AVB solution can cope with changing levels of usage and equipment, and, unlike MADI and other point-to-point methods, will serve many sources and destinations. In short, AVB could prove to be a cheap, flexible alternative to the mass of spaghetti wiring you see in many broadcast facilities today.

Before implementing AVB into Hydra2, we sought partners that could help us speed up our AVB development. Our membership in the AVnu Alliance, whose primary concern is to guide and support AVB development and provide accreditation for new products, gave us access to information and services that have proven invaluable during development.

We also worked with LabX, a U.S. company with strong experience and a proven track record in AVB interface IP. LabX provided a tried and tested IP design that we have implemented in Calrec-designed hardware. Through this partnership, our customers get the benefit of LabX’s mature IP combined with Calrec’s highly reliable and efficient hardware design.

Thanks to strong partnerships with both the AVnu Alliance and LabX, the implementation came off with no major challenges. In fact, the LabX-Calrec approach has been so successful that we are continuing to work together on a plan for a second AVB interface design with higher capacity. This second interface will run at “wire speed,” meaning that its capacity will be limited only by the capacity of the Gigabit speed of the Ethernet connection, and by the packing efficiency of the AVB streams.

The bottom line: Hydra2 is even better with AVB. Operators of Hydra2 networks can expect a seamless integration of AVB into their Hydra2 environments. AVB channels can be patched as easily as if they were native Hydra2 signal ports. We see AVB as a natural companion technology to Hydra2. In combination, the two can provide powerful, application-specific, broadcast-quality audio network fabrics for the future.

Calrec Audio

Patrick Warrington serves as Technical Director at Calrec Audio.