What is Dolby Atmos and how it works

Dolby Atmos was born in the cinematic field, but has made its way into domestic environments where increasingly advanced devices have “tamed” technology.

Dolby Atmos is perceived as synonymous with cinema sound. It is no coincidence that in recent years many “Atmos theaters” have sprung up in Italian cinemas, where the audio system can offer a more advanced experience than conventional use.

When it comes to domestic Dolby Atmos, things get a little more complicated: configuring an adequate system is not easy and disentangling the compatibility between devices and audiovisual content – now more and more used in streaming and therefore compressed – is one non-trivial effort.

This guide has been written independently by DDAY.it. The editorial staff, however, made use of the support of Samsung, interested, like us, in spreading greater digital and technological awareness of people. In practice, the texts were written entirely by the editorial staff of DDAY.it, without influences from Samsung, but the images were captured on Samsung TV. The indications on the paths to follow and on the use of the modes also refer to Samsung TVs.

In recent years, however,  the number of TVs that support Dolby Atmos has  increased , which this year is also supported by the new Samsung TVs (starting from the QLED 4K Q80B onwards and, for the Neo QLEDs, from the QN85B up to QN900B 8K).

This means that being able to enjoy this immersive audio format is getting easier, although the use of dedicated audio devices, such as soundbars, remains the premium solution. But what exactly is Dolby Atmos and what is it different from the multi-channel Dolby audio we have come to know from DVV onwards?

What is Dolby Atmos and how it works

Dolby Atmos is referred to as an object-oriented sound system . The comparison, it is natural, is with a multichannel system such as 7.1 or 5.1: Dolby Atmos is another thing, however.

To put it simply, Dolby Atmos, compared to classic Dolby Digital, is an audio format that combines multichannel tracks (up to 9.1) with a series of audio elements, to which metadata are associated that indicate where in the environment around the subject must be reproduced. The distinction can be difficult to grasp but it is significant: in classic 5.1 or 7.1 channel multichannel audio, the sound is mixed a priori into 6 or 8 discrete audio tracks, each corresponding to a specific speaker of a multichannel audio system; the yield will therefore depend on how each diffuser is distributed in the room.

In Dolby Atmos, on the other hand, during the creation of the track the sounds are arranged on a virtual stage that surrounds the listener at 360 degrees, regardless of how many speakers / channels the audio system used during the listening phase will then be composed.

In other words, the role of Dolby Atmos is to envelop the subject with sound. If we imagine a scene where it rains, through Dolby Atmos the various sound particles are positioned around the person to perceive the three-dimensionality of the scene. The audio objects provided by Dolby Atmos are placed, with millimeter precision, by those who created the audio track of an audiovisual content: an amplifier that supports Dolby Atmos takes care of translating those instructions and positioning these audio objects in the environment by performing a sort real-time mixing .

It is an important paradigm shift from classic multichannel audio, where the position of a sound in space is tied to which of the 5.1 channels it has been assigned to. On the other hand, with Dolby Atmos it will be the device used for playback, depending on the speakers actually available, exploiting the metadata encoded in the Dolby Atmos track to “sort” the sounds appropriately on each channel in order to respect the positioning in the 360-degree space surrounding the listener.

Precisely because we are talking about 360-degree audio, potentially it also serves to represent the vertical dimension, which is why the most sophisticated audio devices that support Dolby Atmos include speakers facing upwards or the possibility of installing additional ceiling speakers ; in these cases, we are talking about 5.1.x channels (where the third number is the quantity of integrated upward facing speakers or, for home theater amplifiers, the channels dedicated to the speakers to be installed in the ceiling).

An interesting aspect to underline is that even in the case of only two speakers, as in many entry level TVs or soundbars, Dolby Atmos allows through virtual surround techniques to respect the creative intent of those who created the audio track.

It is urgent to point out that Dolby Atmos is not technically a CODEC . Dolby Atmos relies on three Dolby audio encodings: Digital Plus, TrueHD and MAT (abbreviation for Metadata-Enhanced Audio Transmission).

TrueHD is the lossless version (ie without loss of quality), which is used in those formats, such as Blu-ray Disc, where it is not necessary to save on data; while Digital Plus is used above all by streaming applications, where it is necessary to compress the flow of data to facilitate transmission: if platforms such as Netflix or Disney + used the TrueHD codec, the data flow would be excessive for many network connections and would consume a significant number of resources (too many).

MAT is a different thing and involves those devices, such as game consoles, which, since they reproduce scenes in real time (think of video games, in fact, which are different from a pre-recorded movie and always the same) need to generate a Dolby Atmos track in real time based on what happens on the screen (the player moves behind a crate or the car goes off the road, for example).

A feature of Dolby Atmos is that it is a scalable solution . In practice, if Dolby Atmos content is played through a device that does not support it, then the audio track can be played in 7.1 or 5.1 “normal” or even stereo. In practice, Dolby Atmos must be understood as an addition to the other audio information: devices that do not recognize the information of the Atmos, ignore it and reproduce the classic multichannel mixes.

What content supports Dolby Atmos

Dolby Atmos is increasingly used by streaming applications, interested in increasing the attractiveness of their content by adding an object-oriented audio format such as the Atmos to the 4K resolution: 4K plus Dolby Atmos is a good match for an experience. movie-like in a living room.

Not surprisingly, for example, Netflix offers Dolby Atmos only as an additional option for those who subscribe to the Premium plan, which includes a stream in 4K. In the case of audiovisual content, in any case, it must be emphasized that  sometimes the Atmos audio track is only provided for the English language  and not for the Italian one.

The first contents that support Dolby Atmos are precisely those included in the catalogs of platforms such as Prime Video, Netflix, Disney + or Apple TV +.

“Tom Clancy’s Jack Ryan” is one of the contents that on Prime Video also includes audio in Dolby Atmos

Then there are the audiovisual contents in physical format, that is Blu-ray Disc and Ultra HD Blu-ray: this is the best version of the homemade Dolby Atmos because, unlike the streaming platforms, there is no need for compression and it is used the Dolby TrueHD codec.

Dolby Atmos has also been implemented by some music streaming services , such as Apple Music (in which case, however, you need an Apple TV 4K connected to the TV or a soundbar) and Tidal (which needs an Apple TV 4K, a Fire TV or an Nvidia Shield TV connected to the TV for those TVs that do not integrate the native application). These services also include dedicated playlists that include only Dolby Atmos songs.

Finally, Dolby Atmos is also supported by video games. Some video games support Dolby Atmos through consoles such as Xbox Series X | S, Xbox One X and Xbox One S ; PS5 does not support Dolby Atmos for video games (as it has its own three-dimensional audio system). Some of the Dolby Atmos compatible games are Borderlands 3, Gears 5, Halo Infinite, and Tom Clancy’s The Division 2.

Dolby Atmos at home on TV

Although its maximum expression is that of cinemas, Dolby Atmos can also be enjoyed in a home environment . More and more devices support this technology and in recent years this also includes TVs.

For many years, the thinning of TVs meant that there was less and less space for advanced speakers: the audio was sacrificed on the altar of the image and the minimum size.

The rediscovery of audio quality, however, has pushed towards greater attention also in TVs, especially in consideration of the new role that this device plays as a center of entertainment: the fact that a TV supports Dolby Atmos implies that a soundbar is not needed to enjoy Dolby Atmos object-oriented audio. It should be noted, however, that a dedicated audio device such as the soundbar has capabilities that a TV, since it is a more general-purpose product, often does not achieve.

The most advanced HDMI connections also include eARC (Enhanced Audio Return Channel) functionality, which is an improved version of ARC. Through ARC, a TV can supply audio to an external system. The basic ARC supports Dolby Digital Plus, which we said is the one used by streaming platforms; while the eARC also supports Dolby TrueHD, a lossless codec.

In normal use, an external source, such as a Blu-ray player, is connected to a soundbar, which in turn is connected to the TV via the HDMI port.

When the user uses a TV that supports Dolby Atmos, if he wants to watch a movie through a streaming service (used through the native application), an external device is not needed: the speakers integrated into the TV will take care of processing the Atmos audio. In the case of external media, such as consoles or Blu-ray players, the latter will also need to support the Atmos in order to enjoy the experience.

Finally, an important distinction must be made: some TVs are “Dolby Atmos compatible”, ie they can transmit (via ARC or eARC) the information to an external device, such as a soundar, which then reproduces the Atmos sound; and there are TVs that fully support the Dolby Atmos format and therefore, by virtue of the built-in speaker configuration, are sufficient to play Dolby Atmos tracks independently. A very important difference.

 

by Abdullah Sam
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