Roles and Accessibility

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Introduction

Audio source data may be used in order to provide details of the audio content source. In general, such characteristics of audio are logically independent of the compression format. In the context of DASH they are typically used in order to select a proper Adaptation Set. This section focuses on source format description.

In the context of DASH as specific source descriptor exists, namely AudioConfiguration identifies channel configuration signaling for Representations that contain an audio component.

In addition, source data properties may be expressed by one of the following two descriptor elements:

  • EssentialProperty: In this case the Media Presentation author expresses that the successful processing of the descriptor is essential to properly use the information in the parent element that contains this descriptor.
  • SupplementalProperty: In this case the Media Presentation author expresses that the descriptor contains supplemental information that may be used by the DASH client for optimized processing.

A multitude of source properties may be expressed using these generic descriptors, some of them using the definition in ISO/IEC 23001-8 [4]. These are listed below.

Audio Channel Configuation

For the element AudioChannelConfiguration the @schemeIdUri attribute is used to identify the audio channel configuration scheme employed.

The following defines URIs that identify specific audio channel configuration schemes, i.e. schemes contained in the AudioChannelConfiguration element:

Identifier Reference Abstract
urn:mpeg:dash:23003:3:audio_channel_configuration:2011 ISO/IEC 23009-1 [1], 5.8.5.4 This URI is used to indicate the channel configuration. The @value is the value as defined for OutputChannelPosition in ISO/IEC 23001-8 [4].
tag:dolby.com,2014:dash:audio_channel_configuration:2011 n/a Dolby audio channel configuration information.The @value attribute shall contain a four digit hexadecimal representation of the 16 bit field that describes the channel assignment as defined by table E.5 in ETSI TS 102 366 [14] where left channel is MSB.For example, for a stream with L, C, R, Ls, Rs, LFE, the value shall be “F801” (hexadecimal equivalent of the binary value 1111 1000 0000 0001).

Generic Audio Source Descriptors

The following defines a set of URIs that identify audio source descriptions to be used with the Essential Property and/or the Supplemental Property descriptor:

Identifier Reference Abstract
urn:mpeg:mpegB:cicp:OutputChannelPosition ISO/IEC 23001-8 [4], 8.1 Audio channel assignment specifies the association of loudspeaker positions to a given audio channel
urn:mpeg:mpegB:cicp:ChannelConfiguration ISO/IEC 23001-8 [4], 8.2 Audio channel configuration specifies the channel configuration. This defines the number of audio channels and their associated loudspeaker positions.
urn:mpeg:mpegB:cicp:ProgramLoudness ISO/IEC 23001-8 [4], 8.3 Audio program loudness level indicates the overall loudness of the corresponding audio program.
urn:mpeg:mpegB:cicp:AnchorLoudness ISO/IEC 23001-8 [4], 8.4 Audio anchor content loudness level indicates the loudness of the anchor elements of the corresponding audio signal (usually the dialog).
urn:mpeg:dash:23003:3:audio_channel_configuration:2011 ISO/IEC 23009-1 [1], 5.8.5.4 This URI is used to indicate the channel configuration. The @value is the value as defined for OutputChannelPosition in ISO/IEC 23001-8 [4].