BBC tests 4.0 surround for The Proms

The annual Promenade concerts feature extra sound coverage this year
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The BBC Proms are the epitome of British tradition (with Rule Britannia and Land of Hope and Glory on the Last Night), but the concert season, broadcast on BBC TV and Radio 3, has become a showcase for innovation, not just with experimental and modern music, but also new technologies to bring the atmosphere of the Royal Albert Hall to the listener and viewer. (Pictured is the star of one of this year's Late Night Proms, Laura Mvula.)

To enhance the listening experience this year the BBC is testing 4.0 surround sound over the internet. The intention is for people round the world to be able to receive the live online transmissions using a standard connection, "a suitable web browser", a surround sound card or HDMI output and a loudspeaker set-up with at least four speakers.

The experiment is being run by Radio 3 and BBC R&D and is, comments Rupert Brun, head of technology for BBC Radio, a continuation of the broadcaster's aim to "bring the listener at home an exciting, immersive experience when listening to live concerts". This, he says, begin in 1958 with stereo, followed in the 70s by quadraphonic sound and in recent years "wide dynamic range high quality stereo (HD Sound)".

The 4.0 online broadcasts are based on HTML5, which includes an Audio API (application programming interface) that enables web browsers to play surround sound without the need to download and install special software. Brun explains that because HTML5 also features the Mediasource API the MPEG-DASH (Dynamic Adaptive Streaming over HTTP) media delivery standard, which is able to adjust the bit stream according to the available bandwidth, can be used to carry the data.

Brun says not all web browsers currently support HTML5 - and the Mediasource API in particular - but that tests proved Chrome on Windows 7 and Mac OSX did work. According to the frequently asked questions section of the BBC R&D site on this subject, Internet Explorer 11 will run it on Windows 8.1 only, while Safari, Opera and Firefox "do not support one or more of the required features at this time".

To create the surround mix additional microphones have been placed in the Albert Hall to supplement those already used for the standard Radio 3 stereo broadcast and the 5.1/stereo set-up for BBC Television. These extra mics are, explains Brun, "to offer a sense of the space and acoustic". The stereo and surround mixes are made in BBC Radio Resources outside broadcast truck Sound 3, which is equipped with a 40-fader Stagetec Aurus digital console.

Brun says the 4.0 format was chosen because the existing operational set-up is based on stereo. He adds that people do not need to worry about the centre or LFE channels as audio is not being sent to them but that some systems with small loudspeakers will run all the bass through the subwoofer, meaning it must be connected.

BBC R&D is encouraging reaction to the surround sound Proms on its blog and Twitter feed.

Photo: Helen Aitchison


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