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Dolby Atmos audio technology migrating from theater to home

updated 10:35 am EDT, Sat August 16, 2014

New technology backwards compatible with Blu-Ray, other content delivery

At an event earlier this week, Dolby announced a technology moving from the cinema to home theaters that challenges the channel-based stereo paradigm. Dubbed Dolby Atmos, the new protocol -- which is fully backwards compatible with older Blu-Ray players and other content delivery mechanisms -- uses up to 34 speakers to more accurately play back a moving sound, and enhance the home theater experience.

Dolby engineers believe that as home theater expanded to 9.1 and even 11.1 systems, problems of pursuing more and more channels were aggravated. Home theater content often originates from theatrical content that is mixed in 7.1 sound as a best case and, many times, in 5.1. The cinema-supplied mixes with fewer channels means that 9.1 or 11.1 systems reached a point of diminishing returns in parsing and upmixing the limited signal to serve more and more channels.

The company also notes the challenge with multi-channel stereo in simulating reality. The example given by Dolby is the complex and non-linear nature of a hummingbird's flight captured on film. Moving the sound from the left height channel to the right front channel loses details, and detracts from the brain's sense that what it's watching is real.

Dolby Atmos is based on the concept of each sound source being a discrete "sound object." In the cinema, Dolby Atmos relies on a combination of 9.1 "bed" channels and up to 118 simultaneous sound objects to deliver an enveloping sound scene. Each of those sounds comes from a specific location in the scene, and can be in motion as well. The original recording tracks both the source and the vector of motion, with the receiver doing the locational sound translation during the decoding process.

Dolby has now developed the technology required to translate the Dolby Atmos experience in cinema to home theaters. A Dolby Atmos reciever (AVR) processes the audio from the feature, and decodes in real time exactly which speakers it needs to use from moment to moment to replicate the transition of the sound.

A Dolby Atmos movie can be played back on nearly any speaker configuration, from a 7.1 system all the way to 24 speakers on the floor, and 10 as upper channels, which is the current maximum that the Dolby Atmos protocol can handle. Speakers can be added by the home user as budget allows in pairs, and the more speakers utilized, the more precise the audio positioning becomes.

Dolby has added extensions to existing Dolby TrueHD on Blu-Ray and Dolby Digital Plus to support Atmos sound, making Blu-Ray players and streaming devices compatible with the technology with little additional investment, other than a compatible receiver.

A Blu-ray player that fully conforms to the Blu-ray specification can play a Dolby Atmos movie without a firmware update. Additionally, HDMI 1.4 and later fully support Dolby Atmos. The Atmos content will be delivered through video-on-demand, broadcast, and cable services that use multichannel Dolby Digital Plus in their core architecture.

Both Dolby TrueHD and Dolby Digital Plus with Atmos data are backward compatible with older receivers and systems. If a movie mixed in Dolby Atmos is played on a non-Dolby Atmos system, traditional 5.1 or 7.1 audio will be played, depending on the type of system owned.

The audio can be encoded with Dolby TrueHD at multiple sampling rates including 48 and 96 kHz, and 16- and 24-bit depths. Dolby Atmos-enabled receivers will also support legacy Dolby TrueHD bitstreams at multiple sampling rates including 48, 96, and 192 kHz and 16-, 20-, and 24-bit depths to provide full backward compatibility with legacy Blu-ray disc media and Dolby TrueHD music files.

For upper channels, Dolby has two solutions -- either integrated Dolby Atmos enabled speakers with an upward-firing speaker, or Atmos-enabled add-on speaker modules which only include upward-firing speakers. The speaker modules can be placed on top of existing speakers, or a nearby flat surface.

Best results come from flat ceilings, made of an acoustically reflective material like drywall, wood, or plaster. Dolby designed the technology for rooms with ceiling heights of around nine feet, but ceilings up to 14 feet still are nearly as good. Dolby claims that recessed lighting fixtures, chandeliers, crown molding, and heating or air conditioning vents in your ceiling do not noticeably interfere with the sound quality from the upper channels.

The first feature film to use the technology was Pixar's Brave in July 2012. Since then, studios have released more than 100 films in Dolby Atmos, including the entire series of The Hobbit, The Expendables 3, Guardians of the Galaxy, Noah, Metallica Through the Never, and Disney's Planes.

The technology won't improve conventional mixes, so cinemaphiles specializing in classic theater, or for that matter, any title recorded before the 2012 introduction of the technology, won't see any benefit. However, movies and other media recorded with Dolby Atmos will demonstrate the improvement -- adoption of the technology by content producers is expected to be widespread by the end of 2015.

Manufacturers who have announced Dolby Atmos AV receivers or processors include Denon, Integra, Marantz, Onkyo, Pioneer, Steinway Lyngdorf, and Yamaha. In addition, Trinnov Audio has plans to release a 32-output processor in support of Dolby Atmos. Definitive Technology, Onkyo, and Pioneer USA have all announced a line of Dolby Atmos enabled speaker modules. More partners will be announcing Dolby Atmos enabled products through the coming months.

by MacNN Staff




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