ISDN and broadcast industry

ISDN is used heavily by the broadcast industry as a reliable way of switching low latency, high quality, long distance audio circuits. In conjunction with an appropriate codec using MPEG or various manufacturers proprietary algorithms, an ISDN BRI can be used to send stereo bi-directional audio coded at 128 kbit/s with 20 Hz-20 kHz audio bandwidth, although commonly the G.722 algorithm is used with a single 64 kbit/s B channel to send much lower latency mono audio at the expense of audio quality. Where very high quality audio is required multiple ISDN BRIs can be used in parallel to provide a higher bandwidth circuit switched connection.

BBC Radio 3 commonly makes use of three ISDN BRIs to carry 320 kbit/s audio stream for live outside broadcasts. ISDN BRI services are used to link remote studios, sports grounds and outside broadcasts into the main broadcast studio. ISDN via satellite is used by field reporters around the world. It's also common to use ISDN for the return audio links to remote satellite broadcast vehicles.

In many countries, such as the UK and Australia, ISDN has displaced the older technology of equalised analogue landlines, with these circuits being phased out by telecommunications providers. IP based streaming codecs are starting to gain a foothold in the broadcast sector, using broadband internet to connect remote studios. However reliability and latency is crucially important for broadcasters and the quality of service offered by ISDN has not yet been matched by packet switched alternatives.

November 23, 2011

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