KitPlus 111

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TECHNOLOGY Bruce Devlin Object Audio What’s all the noise about? We all know that getting the audio right makes the pictures better. Anyone who has seen a movie created for Object Audio like Dolby Atmos will know that there is something special about it. To figure out what that is, let’s rewind a little and see why we might need it. Remember the good old days of mono audio on TV? Mono audio gives a single channel of sound played back through one or more speakers. That’s fine for many genres, but to increase the feeling of being in the scene, stereo audio was introduced, so that left and right channels are transmitted, giving our ears the ability to hear sound moving on either side of us – like we do in real life – while we watch the images And one low bandwidth channel (this it the “.1”) • Low Frequency Effects (LFE) This system essentially takes a sound mix from the program creator that is mastered on 5.1 speakers and then maps it on to the 5.1 speakers in your home or in the theater. Audio processing technology is now very cheap – your cellphone can do more audio processing than dedicated hardware from the 1990s. We have much bigger screens today, and with the rollout of UHD, it is likely that we will be sitting even closer to them. To increase the sense of “being there,” adding a vertical element to the sound can make a dramatic difference. It is impractical to move from a situation where we have six fixed speakers to one where we have hundreds of speakers that position the sound exactly, especially when most of the time there will be little or no sound coming from an individual speaker. Imagine instead a “bed” of audio that is the traditional stereo, or 5.1, mix that you add effects or objects to with an audio stream and some control metadata. Each cinema may have a different number and position of speakers depending on budgets. The object sound systemprovides the “bed” of audio that is mapped onto the speakers in the theater. Each object sound is then mapped to one or more physical speakers at the right time and the right volume to provide very specific spatial effects for the audience. Knowing these basics, you can see how this system might map to a consumer setup where there will be fewer speakers, but by calibrating the room, a sound processor could do a good job of mixing the sound between spatial speakers and upward firing speakers to give a pretty good approximation to the 3D sound experience in the cinema. Currently, we send our content to the listening / viewing environment in a fairly linear way. The mix that is created at the content provider is the mix heard / seen by the viewer. Technologies like IMF are enabling content creators to With the advent of cheaper electronics, produce and distribute versions more we moved to a surround sound system cheaply. Technologies like object sound where we added more speakers to give the with consumer audio processing units impression that sounds could come from in In its simplest form, the UK’s audio allows different objects like languages, front and behind as, as well as either side of description service does just that. Start with high dynamic range effects (for quiet a stereo “bed” that is the normal program us. Typically, today these surround sound environments) and low dynamic range systems use 5.1 channels. This means that mix and then add a description for the effects (for noisy environments) to be visually impaired and a control track that we have 5 full bandwidth channels: selected and / or mixed at the receiving adjusts the volume and position (left-right point. We’re increasingly moving from • Left Front pan) so that a smart decoder can mix the a linear “here’s my content” world to a • Center sound together. component “which bits of the content • Right Front will give you the best experience” world. A full cinematic system is very similar, but • Left Rear with more objects and more metadata. It’s a fun time to be in technology. • Right Rear 36 | KITPLUS - THE TV-BAY MAGAZINE: ISSUE 111 MARCH 2016 TV-BAY111MARCH_Book.indb 36 11/03/2016 17:17