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BBC R&D White Paper WHP170

Standardising Audio Contribution over IP Communications
P.A. Stevens and M. Zemack

Keywords
RTP, SIP, SDP, UDP, VoIP, ACIP, NMC, aoip, G.711, G.722, MP2, PCM, PJSIP, Voice, Asterisk, Server, Outside Broadcast, TECH 3326, TECH 3329

Abstract
Live audio contributions from reporters have traditionally been submitted using standard telephone lines via ISDN. With improvements in the Internet and other access IP technologies, such as wireless hotspots, reporters saw the potential for greater flexibility from where they could contribute their programme material. ISDN is gradually being replaced and so contributions would have to be transferred over IP. This brings its own problems, not the least being, that until recently, IP codecs* from different manufacturers would not communicate with other.

Based on an initiative from German vendors and broadcasters, the EBU** has created a standard for interoperability for live audio contribution over IP. One requirement was that manufacturer claims of interoperability could be independently tested. To achieve this, a reference implementation of the interoperability standard was developed jointly between BBC and IRT***.

This paper describes an overview of the history and background of audio contribution over IP, together with the development of the reference implementation and some possible future developments within the audio over IP field. The reference implementation is based on open source code and is publicly available as an open source project.

This paper also includes a section on the use of the reference implementation in a ‘Plug Test’ that took place with manufacturers at IRT in February 2008.