Dolby’s Brett Crockett, introducing the company’s Atmos format for home theaters. BURBANK, CA—Having introduced Dolby Atmos to mix stages and movie theater screens worldwide, Dolby Laboratories is now turning its attention to delivering the immersive sound format to home theaters—and, eventually, mobile devices. At a recent presentation in its Burbank offices, Dolby outlined the object-based format’s capabilities and unveiled its solutions for the home.
Brett Crockett, the company’s senior director, research sound technology and the man behind Dolby Atmos, reported that his team had gone back to basics to develop a home theater solution: “We had to understand how people hear, how people listen; investigate the science of sound. We needed to make the home Atmos system as engrossing as the cinema— and I think we’ve done it.”
Each sound object in Dolby Atmos— and there can be up to 128 playing simultaneously—has its position in, and trajectory through, three-dimensional space described by accompanying metadata. In the movie theater, the Dolby Atmos processor, having been programmed with the number, location and capabilities of the installed speakers, outputs a custom mix on the fly specific to that environment. “That’s why a 3,000-seat cinema with up to 64 channels of speakers gives a similar experience to a smaller presentation, like this cinema [at Dolby’s Burbank office] with 35,” said Crockett.
Dolby has positioned Atmos, which in cinemas plays back through speakers arrayed on the ceiling as well as the traditional behind-the-screen, side and rear-surround speakers, as a creative tool for filmmakers. “It’s not about channels and speakers anymore; it’s about what sound you want where to help tell a story,” Crockett said. The format adds verisimilitude to a soundtrack: “When I go outside, reality has height,” he observed.
In the home, there are challenges to locating speakers on the ceiling, of course. To solve the problem, said Crockett, “We invented a new type of speaker technology: Dolby Atmos-enabled speakers. They’re made specifically to sound just like speakers on your ceiling, from speakers on the ground. It works by an upward-firing speaker—it has a transducer that reflects audio off your ceiling.”
Ideally, the ceiling should be level; if you have a cathedral or sloping ceiling, you’re out of luck. “Our documentation suggests that a ceiling height of seven to 14 feet is optimal for the Dolby Atmos-enabled speakers to work,” said Craig Eggers, Dolby’s director, content creation and playback, home theater ecosystem.
Simply bouncing sounds off the ceilings isn’t enough, however, continued Crockett, since the head, ears and shoulders interact to modify sounds coming from above. “Dolby Atmos-enabled speakers impart that modification to the audio. That gives your brain the cues to think that it’s coming from overhead.”
These new speakers will typically incorporate a single driver (although some may house more) with a very carefully defined directivity pattern, he said. Manufacturers will also be making add-on speaker modules. The up-firing units should be positioned in the four corners, left and right front and rear, or just left and right front, giving rise to new nomenclature: 5.1.4, 7.1.4 and 9.1.2.
Dolby foresees Atmos 7.1.4 systems for home use. Various home theater equipment manufacturers have already announced the rollout of new Dolby Atmos receivers, including Denon, Integra, Marantz, Onkyo, Pioneer, Steinway Lyngdorf and Yamaha. As in the cinema, Dolby Atmos content will play back in a custom mix specific to the system. “You tell it how many speakers you have, where they’re located and what their capabilities are,” when you install the system, said Crockett. “Every Dolby Atmos-enabled receiver or pre-processor has an Atmos renderer, because the full Atmos mix comes into the home.”
Through the use of a new technology, Spatial Coding (not to be confused with competing, similarly-named codecs), Dolby Atmos content may be delivered at highly efficient data rates using Dolby Digital Plus, enabling distribution via over-the-top services, such as Netflix, and Blu-ray Disc. As Eggers explained, that also means that “Dolby Atmos content is 100 percent backwards compatible.”
On a legacy AVR, for example, providing it is 100 percent spec compliant, offers HDMI 1.4 or higher, and the user switches off the secondary audio function (which is used to mixin a director’s commentary), Atmos content will correctly downmix for playback on a channel-based setup such as 5.1 or 7.1, said Eggers. Alternatively, “If your primary soundtrack is Dolby TrueHD [Dolby’s lossless Blu-ray Disc format], and you have a channel-based system, it will play back TrueHD on your channel-based system.” Dolby Atmos Blu-ray titles will reportedly begin appearing in the fall.
As for the potential for mobile playback, said Crockett, “The Dolby Atmos soundtrack has all the three-dimensional audio object information that can be transmitted to a portable device via streaming, and can be sent to the headphone renderer, which renders a three-dimensional representation over any pair of headphones. We’ve also developed technologies that more accurately play back the LFE or .1 soundtrack.”
The headphone rendering software will typically run on the device’s DSP chip. “For mobile, it’s likely that it’s Dolby Digital Plus,” said Crockett. “That would render the objects from the Atmos mix, and then the new Atmos headphone renderer would spatialize it.”
It could alternatively run as an app, “But it’s more efficient in the DSP; top-level apps are more battery hungry.” Dolby Atmos for mobile is scheduled for launch during the next year, he said.