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Playing back immersive audio
Finally, let's play immersive audio, but only when we know that the system is fully equipped for spatial audio.
Dolby Atmos in Dolby AC-4
Learn how to play Dolby Atmos in Dolby AC-4.

Introduction
Before we begin
Playing Dolby Audio
Because not every system has Dolby Audio, we want to first make sure that Dolby Audio plays in our setup.
Querying mediatype support
Not every mediatype is supported everywhere, so we need to detect what the playback system can do and adapt to it.
Implementing fallback in media frameworks
When our preferred datatype is not supported, we need to make sure by way of some fallback logic that audio and video are still playing .
Checking for immersive audio capability
Even when the codec of choice is supported, your system may not be equipped with spatial playback, so we need to check for it.
Playing back immersive audio
Finally, let's play immersive audio, but only when we know that the system is fully equipped for spatial audio.
- Dolby Atmos in Dolby Digital Plus
  Learn how to play Dolby Atmos in Dolby Digital Plus.
- Dolby Atmos in Dolby AC-4
  Learn how to play Dolby Atmos in Dolby AC-4.
- Playing encrypted media
  Sometimes, playing immersive audio as encrypted media works better.
Selecting by language and for accessibility
When everything is said and done, there may still be more than one experience to pick from. Let's find that which best matches the user's preferences.
Bringing it all together
For the grand finale, we will bring everything together: an example with languages, fallback, immersive audio, and accessibility.
Appendix
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Dolby Atmos in Dolby AC-4

Learn how to play Dolby Atmos in Dolby AC-4.

There are differences in how Dolby Atmos is signalled, depending on the mediatype. Unlike Dolby Atmos in Dolby Digital Plus media where Dolby Atmos signaling is explicit, Dolby Atmos in Dolby AC-4 media needs to be detected by checking whether the media contains immersive content. This can be done by inspecting the AudioChannelConfiguration descriptor.

Table 1. Values of ChannelConfiguration that signal immersive content
Channel Configuration	MPEG AudioChannelConfiguration value (ISO/IEC 23091-3)	Dolby AudioChannelConfiguration value (ETSI TS 103 190-2)
Channel Configuration	`urn:mpeg:mpegB:cicp:ChannelConfiguration`	`tag:dolby.com,2015:dash:audio_channel_configuration:2015`
5.1.2 ^[a]	'14'	'0x0000C7'
5.1.4	'16'	'0x000077'
7.1.2	N/A	'0x0000CF'
7.1.4	'19'	'0x00007F'

[a] The MPEG channel configuration 5.1.2 uses different positions for the height channels in comparison to Dolby's 5.1.2 channel configuration. In both cases there are height channels, thus both cases are considered Immersive audio.

Considering the callback function from the previous lesson, a filter function to remove immersive channel configurations from the set of possible AdaptationSets can look like:

Figure 1. Filter for Dolby Atmos/Dolby AC-4 support in dash.js