The Festival of Nine Lessons and Carols in surround sound
An early TV recording of Carols from King's (1963) Photo © BBC Rupert Brun, head of technology for BBC Audio & Music, invites you to participate in a seasonal surround sound experiment.
An early TV recording of Carols from King's (1963) Photo © BBC
Rupert Brun, head of technology for BBC Audio & Music, invites you to participate in a seasonal surround sound experiment.When the BBC moved its Research and Development function from Kingswood Warren in 2010, Andrew Mason, one of our audio research engineers, discovered an experimental stereo recording of the 1958 Festival of Nine Lessons and Carols from King's College, Cambridge. In 2007, Steve Richards, one of the BBC’s senior sound supervisors, made another experimental recording of the Festival, this time in '4.0' surround sound. For Christmas this year we are offering a technical evaluation of various surround sound formats based on these recordings. There are a number of reasons why the Festival of Nine Lessons and Carols continues to be a popular event for technical experiments of this kind.
- The rich, reverberant acoustics of King's College Chapel, and the location of choir, organ and congregation give us a complex and immersive audio landscape to reproduce.
- At Christmas we hope you will have time to sit down and really listen to this famous annual event. You may even have some new technology as a Christmas gift to help you enjoy it.
- The 1958 experimental recording gives us an interesting story to tell and the engineers a wealth of material to experiment with.
The 1958 recording
It might seem impossible to create true surround sound from a stereo microphone but we hear three-dimensional sound with only two ears, so there is no fundamental reason not to create surround sound from just two microphones – but it does require a great deal of computer processing to do it. I wonder what the engineers who recorded it, thinking stereo was 'cutting edge', would have made of our surround sound rendering of their recording? The service was recorded using a single pair of microphones mounted close to each other in an arrangement known as a 'coincident pair' which captured a great deal of the ambience of the chapel and the shuffling and coughing of the audience is clearly audible.
The 2007 Recording
Traditional surround sound uses a central speaker. This is useful in the cinema; it anchors dialogue to the centre of the screen even if you are sitting to one side of the room. But a central speaker and a layout focussed around a screen aren’t ideal for radio. If you are trying to distribute an orchestra evenly across one end of your living room, the centre speaker can make all the violins sit in a heap in the middle. Of course it is possible to create a good '5.1' surround sound mix of orchestral music but it needs to be a completely different mix from that used for stereo. Our 2007 recording avoids the problems associated with the centre speaker by using a '4.0' presentation, or 'Quadraphonic Sound' as it used to be called. We think this gives a good surround sound experience for this type of content and because it is based on the stereo mix, one recording engineer can potentially produce both at the same time making it an affordable option for radio. The recording used a number of microphones which were then mixed together to create the surround mix.
How to Listen via loudspeakers
This work is enabled by a BBC collaboration with Fraunhofer IIS in Germany who are providing the sophisticated computer algorithms and the surround codec that make the coding and streaming possible. You will need to download from Fraunhofer IIS the special player and install it on your computer. At present the player is only available for the Windows platform. Once you have installed the player you will be able to listen to both the recreated surround sound of the 1958 recording and the specially recorded 4.0 2007 recording. You will need to connect a computer with a surround-sound output directly to suitable amplifiers and speakers. The mix is intended to be replayed on the four 'corner' speakers of a standard 5.1 layout: you can find a diagram by following this link. You can replay the experiment through your 5.1 home cinema system by connecting to it with four separate cables or using an HDMI lead. You should not hear anything coming from the central speaker for the 2007 recording.
How to Listen on headphones
The headphone experience does not require the special player; any computer with a stereo output will work. To create realistic immersive sound on headphones is nonetheless quite a challenge – the signal has to be processed by BBC Research and Development into the binaural format and this processing should ideally be different depending on the type of headphones you are using and the size and shape of your head and ears! In the laboratory we can calibrate the equipment for each listener, but for this experiment we have produced a number of different binaural renderings of the Festival of Nine Lessons and Carols for you to try. There are three different versions of the 2007 service available for in-ear headphones and three for over-the-ear headphones. If the binaural sound works for you, you should experience the effect of listening to four speakers in a room including some front-to-back localisation of the sound.
The following audio files have been optimised for different head shapes and listening devices. We recommend that you listen to the beginning test signal of each file until you find the best version for your set-up, then continue with that version to listen to the service.
BBC R&D would like to know which binaural version works best for you: please take a moment to let us know by following this link to complete a very short survey. If you want to know more about the way in which we have produced the binaural files, you can watch a short video produced by Anthony Churnside from the BBC’s R&D department.
How to give feedback
Neither of these recordings was originally intended for public consumption in surround sound: nonetheless, we think you will find them interesting and welcome your feedback: you can comment directly on this page, and If you want to discuss the experiment on social media such as Twitter, the hashtag is #BBC9LC.
There is also another questionnaire, which will ask you about your experience with surround sound – part of the questionnaire covers your experiences with our experimental (Fraunhofer) player available here, but there are also general questions about surround sound that we would like to know your views on… whether you can install the player or not. So we’d ask anyone to provide us feedback via this questionnaire. (It also asks whether you are on Mac – as we know our experiment only currently works on Windows – so you may like to feed that back to us!
Thank you again!
Rupert Brun, head of technology, BBC Audio & Music