Surround Encoding and Monitoring
Feb 1, 2013 9:00 AM, By Kevin Becka
THE WIDE-RANGING OPTIONS OF MULTICHANNEL PLAYBACK
If there were one phrase that best describes the state of surround audio production today, it would be “ever-changing.” Surround is still trying to find itself across film, television, gaming, audio-only and, ultimately, the portable delivery systems. It seems that on the high-end, in event spaces such as theaters, the channel count will only go up, while in the home and on mobile sets, the move is toward refinement of the surround experience and re-creation of the immersive field out of headworn sets.
Last year, Dolby, the worldwide leader in surround encoding across nearly all platforms, debuted a revolutionary technology called Dolby Atmos, an object-based system that can accommodate up to 62.2 channels for theater playback through a proprietary decoder. Dolby also works continuously with companies like Intel and Nokia, on the chip level, to make surround easily portable. DTS, meanwhile, Dolby’s chief rival on the high end, created some buzz at CES a few weeks ago with DTS Headphone:X, which delivers 11.1 for headworn playback. GenAudio’s AstoundSound is finding traction in the encode for 2-channel headphone and speaker listeners. And there are a couple of heavy hitters in the headworn device market that have created some impressive products that provide a believable playback experience, even when the listener is moving.
For the companies that make physical surround playback products and develop algorithms, a major hurdle has been to provide broad distribution of quality playback. This is especially daunting with the consumer’s love affair for portable devices. For engineers, the frustration has always been how to get all listeners to have the same or similar experiences when playing back their mixes, no matter the format. The past few years have revealed a separation between technology developments for the big theater experience and on your phone while you ride public transit. Yet both areas have to be addressed in delivery. They have to also be addressed on the front end.
The release of Dolby Atmos has been followed by early adoption on the high end, with Skywalker Sound, Todd-AO and Warner Bros., among others, installing systems. While you can get up to a 62.2-channel mix, that isn’t entirely accurate. Those are the limits of the “physical channels.” The system throws out the concept of channels in favor of a hybrid approach to mixing that directs sound as dynamic objects (or sound elements) that envelop the listener, in combination with channels for playback. The flexibility of object-based mixing provides total control over placement and movement of individual sounds or “objects” anywhere within a theater environment.
The rooms used to create the content are equipped with a render mastering unit (RMU), a box the engineer uses to develop and play back the Dolby Atmos mix. While speakers are elements used to get the audio out (5.1 or 7.1, for instance), with Dolby Atmos, sound objects can be placed anywhere in the soundfield, even overhead.
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