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Media Presentation Description with Dolby AC-4 Use proper values in an MPD file to describe a Dolby AC-4 bitstream. Examples of MPD files for different scenarios are provided.
ProfilesA profile imposes a set of specific restrictions, which are typically on features of the MPD files and segment formats.

Introduction to the Dolby AC-4 in MPEG-DASH for online delivery specificationThis documentation is for online delivery (over-the-top services), specifying the required data formatting and signaling between a server (sender) and clients (receivers) to enable Dolby AC-4 to be used as an audio format within the MPEG‑DASH standard in conjunction with the ISO base media file format.
Dolby AC-4 packetization into MPEG-DASH compliant ISO base media files The process of analyzing and preparing a Dolby AC-4 bitstream for storage within an MPEG-DASH compliant ISO base media file is described. AC-4 sync frames must be converted to raw AC-4 frames before packetization.
Media Presentation Description with Dolby AC-4 Use proper values in an MPD file to describe a Dolby AC-4 bitstream. Examples of MPD files for different scenarios are provided.
- Media Presentation Description An MPD can be used to describe media presentations with one or multiple Dolby AC-4 bitstreams.
- ProfilesA profile imposes a set of specific restrictions, which are typically on features of the MPD files and segment formats.
- PeriodsMedia content can be composed of a single period or multiple consecutive media content periods.
- Adaptation sets and representationsAn adaptation set typically consists of multiple representations of the same audio, video, or A/V content. Each representation is associated with a Representation element.
- AudioChannelConfiguration descriptorThe channel configuration for a Dolby AC-4 stream is specified in the AudioChannelConfiguration descriptor.
- Accessibility descriptorThe Accessibility descriptor indicates the presence of accessibility features such as AD, visual description service, or dialogue enhancement.
- MPD for immersive stereo contentTo signal immersive stereo content in the MPD file, an additional SupplementalProperty descriptor must be included.
- ATSC 3.0 specific constraints on Media Presentation Description MPD files for ATSC 3.0 services must adhere to the constraints defined in DASH-IF Interoperability for ATSC 3.0 and the Broadcast TV Profile constraints from ISO/IEC 23009-1.
- Compatibility with ATSC 3.0 and DVB-DASHTo be compatible with ATSC 3.0 and DVB-DASH, required settings must be used for the AudioChannelConfiguration descriptor and the Accessibility descriptor.
- Media Presentation Description file examplesExample MPD files for different media presentations are provided.
Demultiplexing a Dolby AC-4 bitstream from an MPEG-DASH compliant ISO base media file segmentBuffering and parameter conflicts must be considered when product designers implement an ISO base media file format file demultiplexer that supports Dolby AC-4 bitstreams.
MPEG‑DASH and Dolby AC-4 overviewIntroduction about MPEG‑DASH and Dolby AC-4.
Glossary
Notices

Profiles

A profile imposes a set of specific restrictions, which are typically on features of the MPD files and segment formats.

The profiles are signaled by the profiles attribute of the root XML element by one of the following URNs.

urn:mpeg:dash:profile:isoff-on-demand:2011
ISO base media file format on-demand profile
urn:mpeg:dash:profile:isoff-live:2011
ISO base media file format live profile
urn:mpeg:dash:profile:isoff-broadcast:2015
ISO base media file format broadcast TV profile

Additionally, to indicate compatibility with different application specifications, the profiles attribute of the root XML element might contain one of the following URNs.

urn:dvb:dash:profile:dvb-dash:2014
2014 edition of the DVB-DASH profile
urn:dvb:dash:profile:dvb-dash:2017
2017 edition of the DVB-DASH profile
urn:hbbtv:dash:profile:isoff-live:2012
HbbTV 1.5 DASH profile
http://dashif.org/guidelines/dash-atsc-main
Main DASH interoperability point for ATSC

Multiple profiles can be simultaneously specified by providing multiple URNs as a comma-separated list to the profiles attribute.

Profiles for OTT applications

For OTT applications, the ISO base media file format on-demand and live profiles are commonly used.

For OTT content, it is anticipated that, for efficiency reasons, each experience is delivered on demand individually. Thus, for OTT delivery, a Dolby AC-4 bitstream ideally contains just one presentation.

Profile for broadcast and multicast applications

To meet the requirements for DASH delivery over multicast (for example, in a one-to-many, unidirectional way) and ATSC 3.0 broadcast, the ISO base media file format broadcast TV profile is defined. For more efficient bandwidth usage, it is recommended that Dolby AC-4 bitstreams are generated to contain all available audio components in one single elementary stream. One or multiple presentations in the Dolby AC-4 stream use combinations of the available components to provide a given number of audio experiences a user can choose from. To adequately signal these presentations in MPD, the preselection element is defined as part of the new profile.