Auro 3D and Dolby Atmos Compete for 3D Audio Format Supremacy

You may not remember Beta versus VHS, but we were all here for Blu-ray versus HD DVD, and now we have Dolby Atmos versus Auro 3D.
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Sam Cavitt (samcavitt@medesign.tv) is president of Paradise Theater in Kihei, Hawaii, and Carlsbad, California. You may not remember Beta versus VHS, but we were all here for Blu-ray versus HD DVD, and now we have Dolby Atmos versus Auro 3D. While these previous format wars impacted equipment and libraries, competing 3D audio formats will impact the design of private theater rooms. Thus it makes sense for us to take a careful look at what these formats deliver, what they require, and come up with a well-conceived design approach.

As we have seen with the aforementioned technologies, the format war in the professional arena has the ability to shape the resulting 3D audio standards that will reach our industry. While Auro 3D got off to a fast start with extensive presence in post-production facilities and many titles mastered in the Auro 3D format, Dolby Atmos has gained momentum with many studios, including Warner Brothers and Disney, as well and an impressive list of commercial cinemas equipped for the format. Reps for Dolby and Auro 3D publicly discussed working together with studios and theaters to establish standards to allow both systems to coexist. Until then, studios, filmmakers and theaters (both public and private) are caught in the middle. But beyond these content deals, there are significant differences in the way Dolby Atmos and Auro 3D technologies are designed to work.

Channel-based vs. Object-based Systems

The first difference between Auro 3D and Dolby Atmos is that one is a channel-based system and the other is object-based.

In Auro 3D’s channel-based systems, a sound designer mixes the many “sound elements” (dialog, foley stage effects, music, etc.) by distributing them over several audio tracks and directing them to specific channels that correspond to the specific speaker or speaker arrays in a surround playback system. The post-production facility is equipped with these standardized speaker configurations, which must then be matched exactly in playback environments for accurate reproduction of the intended surround material.

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There are significant differences in the way Dolby Atmos and Auro 3D technologies are designed to work. Suffice it to say, however, they both involve a lot of speakers in a room. In Dolby Atmos’ object-based system, the sound elements are combined with metadata that describes how and where the sound element should be reproduced in the playback facility based on numerous criteria (position, level, etc.). The playback system then “renders” the data with respect to the specific speaker configuration utilized in the room to create the desired 3D surround.

Loudspeaker/Channel Configuration Differences

Another difference between these two approaches to 3D audio is how loudspeakers and audio channels are configured.

Auro 3D calls for three layers of loudspeakers. The lower layer is the current 5.1 or 7.1 surround configuration (ITU-R BS.775). The height layer consists of four to seven discrete channels correlated to the lower layer, and the top layer involves one or more loudspeakers for overhead effects.

Auro 3D has established layouts for up to a 13.1 channel system (based on 7.1 with full complement of height and top layer). Smaller systems start with 9.1 (based on 5.1 with four height channels. The actual number of loudspeakers will vary as size of room increases to support multiple rows of seats.

Dolby Atmos approaches this from a different perspective. Supporting up to 128 discrete tracks and 64 speaker feeds, Dolby’s commercial system allows for a lot of customization. Eschewing one-size-fits-all speaker configurations, it enables the designer to create a system that fits the unique acoustical properties of a room’s size and shape. As the processing is an “intelligent” system, speaker placement data and positioning metadata in the audio stream optimize playback for the specific space.

For the home, Dolby has defined a few “reference” speaker configurations to enable the format to be adopted most easily. Reference configurations range from the 5.1.2 configuration, which simply adds two ceiling speakers or Atmos-enabled speakers to a traditional 5.1 surround system, to the 7.1.4, which builds onto a traditional 7.1 system with four ceiling or Atmos-enabled speakers. The hidden gem here, though, is that as an object-based system, the possible configurations are seemingly limitless because its processors “render” the soundtrack to the specific room configuration.

“Content is king in the movie business,” said Steve Shurtz, Meyer Sound’s technology director for cinema loudspeakers. “In the end, the studios will determine which immersive formats they release their films in [for] digital cinemas, Blu-ray, or streaming. Dreamworks Animation is supporting Auro 3D for a number of titles, and the other major studios are mixing films in Dolby Atmos and in some cases, both Atmos and Auro. Both of these formats, and conceivably others, may be with us for a long time.”

So what’s a theater designer to do? Ironically, this latest change means no change in the right way of engineering and designing private theater rooms. It does, of course, add some complexity but also some exciting potential. By stepping up and meeting this latest challenge head on, the private theater industry can improve our deliverables, increase our client’s expectation and appreciation of performance, and enhance our business. If we pass, the trend will go the other way.

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