28 l October 2013
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livefeature
Getting hip to the world of
Audio-over-IP is not only becoming the basis for transmitting and distributing sound in a wide range of situations, it is bringing once disparate areas together. Kevin Hilton reports
LIKE TECHNOLOGIES before it, audio-over-IP (AoIP) was treated with suspicion by broadcasters and post- production facilities. Of those that did see its potential many looked at it in terms of specific functions, such as contribution and distribution links and intercom. But, like ISDN, which it is superseding, AoIP was intended to be a full networking system for carrying audio, video and data. An early broadcast and
professional audio application for AoIP was intercom. The first systems using the technology were introduced in the early 2000s, with Trilogy Communications leading the way. Today all the major intercom companies have systems based on the format. Simon Browne, director of
product management for Clear- Com, comments that what the company has tried to do with
the new technology is “extend intercom”. But, he found, customers wanted to go further. “A couple of years ago at IBC somebody asked whether we did ‘global intercom’,” he says. “I couldn’t answer that then. But it is different now.” That difference has been
made by the continuing development of AoIP in terms of lower latencies and higher quality, combined with digital networks to deliver fast transfer
Axia Audio Element console at Eagle Radio in Guildford, a typical working studio employing AoIP-based tools
AES S67
“With IP we have ubiquity, so it is possible to give global intercom. Concert connects PC to PC, with intercom using the
internet or a LAN so it’s like Skype but on its own server”
Simon Browne, Clear-Com Clear-Com’s Concert scalable, multi-user IP intercom for LANs, WANs or the open internet
speeds. For Clear-Com this is reflected in the Concert scalable, multi-user IP intercom for LANs (local area networks), WANs (wide area networks) or the open internet and the Eclipse digital matrix. “With IP we have ubiquity, so it is possible to give global intercom,” Browne says. “Concert connects PC to PC, with intercom using the internet or a LAN so it’s like Skype but on its own server.” Browne explains that with Eclipse connected to Concert the PCs used “become an extension to the intercom”. He says that being able to connect conventional intercom panels, like the V-Series, to the internet and communicate over distance “seems like magic today” but says there are drawbacks:
THE AEShas been working on an engineering standard for
networked/streaming audio over IP since December 2010. Then known as AES X192 it became a collaborative effort with the EBU in August 2012 and was finally published - as AES S67 – last month, just ahead of IBC. Both organisations say the intention was not to create new technology but to discover “an interoperable subset of existing technologies” to push on the development of AoIP.
The AES acknowledges that high-performance media networks now support professional quality audio – 16-bit, 44.1kHz and above – and can deliver low latency, in the region of less than 10 milliseconds, that is compatible with live sound
“Nothing comes free and the price here is latency. Using V- Series panels with an IP card can introduce latency of approximately 36 milliseconds, which is sufficient to produce an echo on gallery comms speakers. Thirty milliseconds is the magic number because anything over that will give a noticeable delay and echo. People don’t notice 30ms or lower so much.” Clear-Com continued to extend intercom at IBC2013
applications. The kind of network performance, it says, can be found on local area and enterprise scale networks.
What was missing, as the AES saw it, were recommendations for running the various networked audio systems that have been developed in recent years in an interoperable way. AES S67 includes “comprehensive interoperability recommendations in the areas of synchronization, media clock identification, network transport, encoding and streaming, session description and connection management”. It was developed by Task Group SC-02-12-H, under Kevin Gross; copies of AES S67 can be obtained online from:
www.aes.org/publications/stand ards/
search.cfm?docID=96.
with ICON (Intercom CONnectivity) for local or widespread comms over Ethernet/IP networks and/or optical fibre, and Eclipse-HX Matrices, matrix system frames that can give up to 64 nodes of connectivity over fibre interface cards, as well as trunking using four-wire, E1, T1, MADI and Ethernet/IP with low latency over LANs and WANs. Conduit systems were also part of RTS’ offering at IBC.
AoIP
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