The EBU is due to publish a new standard for intercom over IP by the end of this month. As Kevin Hilton reports, this not only reflects the growing influence of IT on broadcast communications and distribution, but also has the potential to make interconnection and the exchange of material quicker and easier.
Both broadcasting and telecommunications have come a long way in the last 25 years. The two have always had a connection; telephone lines and permanent circuits have been a mainstay in getting programmes and contributions between television and radio studios but there was always a strict demarcation between what were regarded as completely different disciplines.
There was a parallel evolution, based on solid engineering principles, with technology developing at a similar rate. Although this benefited both sides there was very little cross-pollination - until computer technologies broke out of their niche to not only influence both broadcasting and telecoms but join the two at a fundamental level.
This is now obvious to the consumer at home, who can have television, the telephone and broadband internet all on a single line. In broadcast studios it means the days of copper contribution and distribution circuits are long gone.
Like most other broadcast organisations, the European Broadcasting Union (EBU) has realised how the tide is turning and adapted telecom techniques for TV and radio. In 2008 it published two standards for audio contributions based on internet protocols: Tech 3326, laying down the basic principles, including interoperability; and Tech 3329, a companion document looking at the practical applications.
Both are based on SIP (Session Initiation Protocol). Developed by the IETF (Internet Engineering Task Force) and published as RFC 3261, this is an internet protocol for live communications that is used to set up and terminate voice or video calls. It is a signalling protocol for creating, modifying and ending sessions involving one or more participants on an IP network.
In telecoms these sessions can be a basic two-way phone call or a multi-media conference involving a number of participants. What broadcasters needed was a way to pass high quality audio between different points.
Codec manufacturers, including AEQ and Glensound Electronics, now produce IP-based equipment for both contribs and distribution. Gavin Davis, managing director of Glensound, has described linear audio over IP as the future, foreseeing a time when ISDN (Integrated Services Digital Network) won't be used any more.
ISDN was the first big move away from dedicated circuits, despite initial doubt and resistance. Just over 20 years later and ISDN is looking as redundant as the copper circuits it replaced.
"Some countries, such as Sweden, are beginning to phase out ISDN, so we had to start looking at new ways of exchanging material over lines," comments Mathias Coinchon (pictured), senior engineer with the EBU technical department who worked on Tech 3326 and 3329. "SIP was a good candidate for setting up codecs. We took the Voice over IP [VoIP] specification and extended it to carry high quality audio, using MPEG2, MPEG4, AAC or aptx."
Now the EBU is applying SIP to broadcast intercom. Coinchon says that although the need for high quality audio is not as critical as it is with contribution and distribution systems, stability and reliability are still crucial for carrying communications between studios and control rooms.
"In a way intercom is like VoIP because of the low latency and bit-rates," he explains. "But we want to align intercom over IP with audio contributions over IP as much as possible and have interoperability between the phone and the codec."
The EBU held a meeting on intercom over IP at IBC 2009, inviting the main manufacturers in the field, including RTS/Telex, Riedel, Clear-Com (now owned by HME) and Trilogy Communications. Comments and suggestions from this session were used to draft initial specifications, presented at IBC last year, which will form the basis of the new standard, due for publication at the end of this month. Coinchon the next step will be workshop tests to see how the different commercial IP intercoms work together.
Trilogy was a pioneer of IP intercom with the Mercury system during the early 2000s. The company launched its next generation product, Gemini, last year and is keen to promote interoperability, moving away from the proprietary approach to systems that intercom manufacturers had followed previously.
"There is the opportunity to achieve more than just routing audio between disparate manufacturers' systems," comments Barry Spencer, general manager of broadcast at Trilogy. "So much broadcast content is being carried over IP these days and the ability for different systems - Trilogy, Riedel, Clear-Com - to talk to each other is seen as viable. The SIP interface is making this possible and if manufacturers don't follow suit they will be left behind."
Mathias Coinchon at the EBU says broadcasters will continue to install one brand of system throughout their broadcast networks but where different broadcasters have to communicate with each other - for example big productions like the Eurovision Song Contest - a common, SIP-based intercom makes sense.