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TECHNOLOGY Object of desire If UHD (Ultra High Definition) is to deliver an immersive televisual experience, it will need more than just highly detailed pictures. It will also need extraordinary sound. Will Strauss examines one of the potential candidates: object-based audio. by Will Strauss I f NAB is a decent yardstick, 2014 is all about 4k and why, when and how it might become a mainstream TV proposition. But in amongst all this pixel counting and discussion about higher frame rates, there is a subject that often gets forgotten but definitely deserves a mention, one that is closely linked to the introduction of 4k: immersive audio. Why? Because having all those extra pixels on a UHD screen is all very well and good but if the audio isn’t similarly enveloping then the experience is lessened. Great pictures need great sound and vice versa. I doubt many will argue with that trueism. As things stand, the associated audio standard for UHD is still being fi nalized. But one approach, the object-based one, looks likely to be involved in some shape or form. Here is my potted guide to object- based audio for broadcast. What is it? A new way of broadcasting sound that allows for a more immersive, interactive and personalized experience. How does it work? I’m glad you asked. Currently, television broadcasts use a channel- based approach for audio, one that if you want to listen to more than just a stereo feed requires a complicated speaker confi guration. Object- based audio is different. Rather than 46 | TV-BAY MAGAZINE: ISSUE 89 MAY 2014 © broadcasting the stereo loudspeaker signals and their pre-mixed combination of dialogue, narration, sound effects, music and background atmospheres, each of those sounds is sent as a separate audio object with associated metadata. The viewing device or system at the other end then reassembles the objects into an output that can be slightly different for each listener by locally changing the metadata. That sounds a bit like responsive website design? It is. Sort of. It certainly uses a set of associated parameters to control how the content should render depending on the type of device it is being experienced on. But it’s probably more like Lego. “When you buy a Lego set it comes with a load of bricks and instructions for how you can assemble those bricks,” explains Tony Churnside, media technologist at BBC Research and Development (R&D). “Sometimes those instructions can provide for the creation for more than one thing. That is what we’re doing with TV or radio programmes.” Why is this of interest? Well, several reasons really. Dolby Atmos, a cinema-based immersive experience, is starting to gain traction in the movie world. And where they go, we often follow. Then there is this potential move to UHD, where, it is assumed, viewers will expect an improved audio experience alongside their visual one. But, at the same time, it is of interest because viewers are increasingly watching television on different devices. When TV was watched on a big old wooden box the audio experience was pretty consistent for everyone. These days TVs are thinner and their speakers and drivers are smaller as a result. There are also other devices – such as tablet computers – for watching and listening to TV. One size (of sound) does not fi t all. So, what might object-based audio offer? Tests have shown that using object- based audio it is possible to optimize the audio experiences for different devices without signifi cant additions to