at ground level, but we had another plane at the same height as the PA speakers, and because big events like these often have firework displays, there was a third level to provide extra oomph for people listening in an immersive world.” WHAT IF WE’RE NOT THERE? This highlights one of the challenges of where we are on the road to full spatial audio, and one of the challenges for sound engineers is how to cater for all listeners. Despite the popularity of 3D soundbars, which bounce height channels off the living room ceiling, and spatial renderers, which create binaural mixes for earbuds, we are all at different points on that journey – and we are not all there yet. The vast majority of people are still living in two-channel stereo world, and not everything is attached to a streaming service which will automatically create a spatial mix for you. “How your fantastic multichannel mix ends up when it is downmixed on TV speakers for the majority of people when they are sat on their sofa is an age-old problem, and a lot of effort goes into ensuring the downmix still sounds good for the majority of viewers,” says Edwards. “In an Atmos presentation, you are often adding information into the height channels, which doesn’t necessarily contribute in a positive way to what you’re doing at the base level, so there’s a balance to be found. If the mix is a totally dedicated Atmos mix and you know all your immersive channels are staying as discrete channels, then that issue is lessened. But you must be aware how much colouration these extra layers add to any downmix most viewers will be experiencing.
AUDIO DYNAMITE For Robert Edwards, immersive audio will find a home in streaming platforms, but while now is the time to be creative, eventually the approach will have to be more commercially minded
“What you have collected in an immersive environment should also have a positive impact to the downmixes. With something like the fireworks, it was vital to make sure that this top layer was not just a Dolby Atmos effect. While promoting the fireworks for the Atmos world in the top layer above your head, I had to be mindful of how to integrate it so it could be heard in the main mix for those listening in stereo.” CHANNELS VS OBJECTS The way we have traditionally experienced audio in live broadcast is channel-based, where each audio channel is mixed to a specific loudspeaker; two channels are fed into two speakers for stereo, six channels for 5.1 surround, 12 channels for 7.1.4 immersive and so on. Spatial audio is different in that it treats some components as independent objects, and an object can be anything from a single commentator mic to a direct stadium PA feed, or fireworks. Each object has associated metadata to describe what it is, such as its level and where it is positioned in space, and immersive scenes are created using multiple objects which each have a place in that scene. Receivers on consumer devices use the information in the metadata to reproduce the
THE VAST MAJORITY OF PEOPLE ARE STILL LIVING IN TWO-CHANNEL STEREO WORLD, AND NOT EVERYTHING IS ATTACHED TO A STREAMING SERVICE
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