AudioChannelConfiguration descriptor

MPEG channel configuration scheme

For all the Dolby AC-4 channel configurations that can be mappable to a value within the MPEG channel configuration scheme, the AudioChannelConfiguration descriptor uses the MPEG channel configuration scheme as follows:

schemeIdUri="urn:mpeg:mpegB:cicp:ChannelConfiguration"

A Dolby AC-4 channel configuration is represented by the presentation_channel_mask_v1 parameter contained in the first presentation_v1_dsi (by order of appearance in the presentation loop) within the ac4_dsi_v1 structure. The following table provides a mapping from ac4_dsi_v1/presentation_channel_mask_v1 to a value within the MPEG channel configuration scheme. The mapping is based on the speaker configurations specified in ISO/IEC 23001-8.

Alternative AudioChannelConfiguration scheme

In some cases, the MPEG channel configuration scheme is not applicable. For example, for a 5.1.2 channel configuration, there is no corresponding value in the MPEG channel configuration scheme. Alternatively, the AudioChannelConfiguration descriptor can use the AudioChannelConfiguration scheme described in the schemeIdUri="tag:dolby.com,2015:dash:audio_channel_configuration:2015".

The value attribute must be set to a six-digit uppercase hexadecimal representation of the 24-bit speaker group index bit field, which describes the channel assignment of the referenced Dolby AC-4 bitstream according to the following table.

For channel-based audio content signaled in the AudioChannelConfiguration descriptor, Bit [0] indicates the presence of the L and R channels. Bits [19] to [23] must be set to 0. For example, for a stream with a 5.1.2 channel configuration of L, C, R, Ls, Rs, TL, TR, LFE, the value element must contain the value 0x0000C7 (the hexadecimal equivalent of the binary value 0000 0000 0000 0000 1100 0111).

Example

The following table shows some examples of common AudioChannelConfiguration values using the Dolby scheme.