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Guide to Dolby Atmos at home

18 Dec 2020 | Rasmus Larsen |

An increasing number of TV makers and services have embraced Dolby Atmos that can deliver a more immersive sound experience. How do you get it and what are the pitfalls? Here is our guide to Dolby Atmos at home, including an updated list of TVs with Atmos (and eARC) support.

What is Dolby Atmos?

Throughout the history of film, sound has been channel-based, i.e. left/right front, center, left/right rear etc. From mono to 4-channel Pro Logic to 7.1 surround sound – and beyond. A movie soundtrack has in other words been mixed to a pre-configured number of channels. Dolby Atmos is based on audio objects on top of a "bed" of channels, typically 5.1 or 7.1, for ambient effects. It means that each sound can be stored as an individual object that can be placed and tracked anywhere in the 3-dimensional space around you. Through accompanying metadata, each sound can be moved around in the 3-dimensional space, if for example a bird flies from left to right. Atmos also introduces overhead sound. Object-based technology is the next step for audio and besides the potential to deliver more immersive, realistic, and dynamic sound effects, it offers flexibility. Content creators are no longer limited to a pre-configured number of channels. The Atmos receiver receives the 'package' and its job is to distribute it to the speakers in that particular setup – a few or many speakers. To do so it relies on a so-called Object Audio Renderer (OAR) developed by Dolby. Dolby Atmos was introduced first in cinema and has since made its way to the home. Initially in movies and now increasingly in music and games. There are other object-based formats, including DTS:X and MPEG-H, but neither are very popular at home so we have decided not to include them here. In theory, many of the same principles apply, although DTS:X is not always object-based.

Dolby Atmos objects Each audio object can be positioned in the 3-dimensional space

Enjoy Dolby Atmos at home

Dolby refers to it as a "revolution" but there are many factors that can influence the experience. Before you can lean back and enjoy Atmos at home, you must invest in the right equipment and content, and make sure that everything is set up in the right way. Atmos is object-based but speaker configurations for Atmos are still described in terms of channels by adding an extra number to the channel designation. Regular surround would often be 5.1 (left/right front, left/right rear, center = 5) plus a subwoofer (.1). An Atmos set-up could be something like 5.1.4 where '4' refers to the number of overhead channels (typically 2 front and 2 rear).
Dolby Atmos objekt-lyd
- "Dolby Atmos can support home theater systems with up to 34 speakers in a 24.1.10 configuration: 24 speakers on the floor and 10 overhead speakers," explains Dolby. "If you play a movie mixed in Dolby Atmos on a non Dolby Atmos system, you’ll experience traditional 5.1 or 7.1 audio, depending on the configuration of your speaker system." Dolby Atmos can be enjoyed at home in one of three ways:
  • Receiver + speakers
  • Soundbar or another pre-configured system
  • Headphones The first option has the potential to deliver a richer Atmos experience but it also takes up more space and is typically more expensive. Dolby has published its recommendations here. More discreet living room solutions are typically offered in the form of an Atmos-compatible soundbar. Some manufacturers highlight Atmos support in TVs but be aware that the benefits of Atmos on built-in TV speakers are limited, although audio objects can be used to enhance voices etc. If you opt for a soundbar you often get up-firing units to simulate overhead effects (by reflecting sound off the ceiling) and sometimes side-firing units that simulate rear speaker effects (by reflecting sound off the walls). These solutions do not match discreet units but technology is improving. FlatpanelsHD has reviewed several Dolby Atmos soundbars here. In a receiver setup, you can opt to install speakers into or on the ceiling, but in a similar fashion some floor speakers come with built-in up-firing units. The best approach here depends entirely on your preferences, budget, and room. Our advice is to ignore budget soundbars. Decent Atmos starts from high-end soundbars and up, or alternatively headphones.

    Dolby Atmos speakers

    The TV's role in an Atmos system

    Regardless of whether you opt for a receiver or a soundbar solution, your TV can play a role. It is further complicated but factors that gain increased relevance as Atmos finds its way to games, live content, and other types of non-packaged content. Traditionally, you would connect the Blu-ray or media player via HDMI to the receiver in order to have the receiver extract audio and let the video signal pass-through to the TV. The same approach works with soundbars equipped with both HDMI inputs and outputs. With the transition to HDMI 2.1 in TVs, this approach will require the receiver or soundbar to support HDMI 2.1 (and optional features like VRR), otherwise the video signal will get downgraded when used in conjunction with next-gen game consoles and players. HDMI 2.1 cannot be added via firmware to existing receivers and the first HDMI 2.1 receivers have issues. This is where HDMI ARC (Audio Return Channel) and eARC (enhanced Audio Return Channel) come into the picture. The system lets you output (from built-in apps ) or pass-through (from an external HDMI player) Atmos via the TV to a receiver/soundbar. A TV can support eARC without featuring HDMI 2.1 ports as eARC can also work on HDMI 2.0 chipsets. Also read: HDMI ARC (Audio Return Channel) and eARC explained The distinction between HDMI ARC and eARC is important because it not only determines audio quality but sometimes whether the Atmos signal even reaches the speakers. Here are examples of common scenarios:

    Atmos, HDMI eARC

    Scenario 1: The full chain is HDMI 2.0 (downstream) so ARC/eARC (upstream) is not relevant. Atmos will work.

    Atmos, HDMI eARC

    Scenario 2: Receiver forces chain down to HDMI 2.0. Atmos will work but video gets downgraded (i.e. 4K120 will not work)

    Atmos, HDMI eARC

    Scenario 3: HDMI 2.1 from console reaches TV with HDMI 2.1. TV then transmits Atmos via eARC

    Atmos, HDMI eARC

    Scenario 4: Apple TV 4K decodes Atmos to PCM (Dolby MAT), which requires eARC in TV (eARC can work on HDMI 2.0 too)

    Atmos, HDMI eARC

    Scenario 5: TV transcodes ATMOS IN PCM (DOLBY MAT) TO ATMOS IN DD+. MAY WORK BUT WILL INTRODUCE AUDIO DELAY (fine for movies but not games). DEPENDS ON TV MODEL

    Atmos, HDMI eARC

    Scenario 6: Apple TV 4K decodes and outputs Atmos as PCM (Dolby MAT), which is not supported by ARC. The TV is not capable of transcoding. Atmos will not work

    Atmos, HDMI eARC

    Scenario 7: TV with Atmos support in streaming apps (in Dolby Digital Plus) outputs Atmos via ARC

    Dolby Atmos can be compressed and distributed from the streaming service or disc in one of two audio codecs. Blu-ray discs carry Dolby Atmos in Dolby TrueHD, a type of lossless compression (not uncompressed), meaning higher audio quality. Streaming services carry Dolby Atmos compressed in E-AC-3 (Dolby Digital Plus), which is 'lossy' compression. It means that some audio information will be discarded leading to lower audio quality. It gets further complicated by the fact that there are two ways to transmit Atmos:
  • Bitstream: Player passes Atmos to receiver/soundbar, which handles decoding
  • PCM with metadata (Dolby MAT 2.0): Player decodes audio before transmitting it
    Atmos bitstream (DD+)Atmos bitstream (TrueHD)Atmos PCM
    A device like Apple TV 4K will always decode Atmos and transmit it uncompressed as Dolby MAT (PCM with metadata), and the same approach is utilized on game consoles like Xbox. It is expected that more devices will use the PCM approach in the future as it ensures low lag, which will be increasingly important for Atmos on game consoles, PCs and distribution systems for live content. Multi-channel PCM has been supported for many years via the 'downstream' link in the HDMI cable, i.e. for Dolby TrueHD or DTS-HD MA from a Blu-ray player to a receiver. However, not with the metadata required for Atmos. To be able to embed metadata into PCM, Dolby has created Dolby MAT 2.0 (Metadata-Enhanced Audio Transport). HDMI eARC (the return channel, or 'upstream' channel) is required to transmit Dolby MAT via a TV. Atmos in PCM is not supported over standard HDMI ARC, but TVs with Atmos support can typically transcode it to Dolby Dolby Digital Plus (Scenario 5) for transmission over standard HDMI ARC. However, transcoding adds audio delay, which works for packaged content like a movie (as the chain can delay the video signal to compensate) but not for live content or games. Check whether your TV model supports it before investing in additional Atmos equipment. In other words: If you are using only your TV's built-in apps (Amazon, Netflix etc) for Dolby Atmos, it should be fairly straightforward. If you are using an external player like Apple TV 4K or Xbox and want to connect it with HDMI to the TV first , we recommend that your TV supports eARC. You can use your existing HDMI cables for Atmos.

    Dolby Atmos soundbar

    List: TVs with Atmos & eARC

    Here is an updated list of TVs with Dolby Atmos support and HDMI eARC. TVs with full support (two blue checkmarks) should be preferred to ensure that you do not run into issues in the future. The list pulls data from FlatpanelsHD's TV database and will update automatically.
    HDMI ARC / eARC:
    TV supports eARC TV supports ARC only
    Dolby Atmos:
    TV can decode Dolby Atmos

    Content in Dolby Atmos

    There are ways to up-mix surround sound to "Atmos" but for the best experience you obviously need content mastered in Dolby Atmos; movies, TV series, games or music. Also read: Full list: 4K HDR & Dolby Atmos movies on iTunes Amazon Video, Apple TV+, Disney+, iTunes (Apple TV), Netflix and Vudu offer movies and TV series in Dolby Atmos. Music in Atmos is available from Apple TV and Tidal.

    Dolby Atmos

    Movies with Dolby Atmos are also available on Blu-ray and UHD Blu-ray. Some Blu-ray movies are available in the competing DTS:X format, which is on the other hand not offered by any streaming services. Xbox One and Xbox Series X/S support Dolby Atmos, DTS:X and Windows Sonic, while PlayStation 5 supports the 'Tempest 3D Audio' format developed by Sony. PS5 supports Dolby Atmos for Blu-ray (bitstreaming) but does not support Atmos in games and apps.
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