AudioChannelConfiguration descriptor

The channel configuration for a Dolby AC-4 stream is specified in the 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.

presentation_channel_mask_v1 in hexadecimal representation Value in the MPEG channel configuration scheme
0x000002 1
0x000001 2
0x000003 3
0x008003 4
0x000007 5
0x000047 6
0x020047 7
0x008001 9
0x000005 10
0x008047 11
0x00004F 12
0x02FF7F 13
0x06FF6F 13
0x000057 14
0x040047 14
0x00145F 15
0x04144F 15
0x000077 16
0x040067 16
0x000A77 17
0x040A67 17
0x000A7F 18
0x040A6F 18
0x00007F 19
0x04006F 19
0x01007F 20
0x05006F 20

Alternative AudioChannelConfiguration scheme

library_booksNote: If applicable, the scheme described by the schemeIdUri="urn:mpeg:mpegB:cicp:ChannelConfiguration" is preferred.

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.

Speaker group index Speaker location
0 Left (L)
Right (R)
1 Center (C)
2 Left Surround (Ls)
Right Surround (Rs)
3 Left Back (Lb)
Right Back (Rb)
4 Top Front Left (Tfl)
Top Front Right (Tfr)
5

Top Back Left (Tbl)

Top Back Right (Tbr)

6 LFE
7 Top Left (Tl)
Top Right (Tr)
8 Top Side Left (Tsl)
Top Side Right (Tsr)
9 Top Front Center (Tfc)
10 Top Back Center (Tbc)
11 Top Center (Tc)
12 LFE2
13 Bottom Front Left (Bfl)
Bottom Front Right (Bfr)
14 Bottom Front Center (Bfc)
15 Back Center (Cb)
16 Left Screen (Lscr)
Right Screen (Rscr)
17 Left Wide (Lw)
Right Wide (Rw)
18 Vertical Height Left (Vhl)
Vertical Height Right (Vhr)
19 Reserved
20 Reserved
21 Reserved
22 Reserved
23 Reserved [a]
[a] For the possible use of this bit, see section E.10.14 of ETSI TS 103 190-2 v1.2.1.

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.

Table 1. Example AudioChannelConfiguration values
Channel layout Speaker locations AudioChannelConfiguration value
1.0 C 0x000002
2.0 L, R 0x000001
5.1 L, R, C, LFE, Ls, Rs 0x000047
5.1.2 L, R, C, LFE, Ls, Rs, TL, TR 0x0000C7
5.1.4 L, R, C, LFE, Ls, Rs, Tfl, Tfr, Tbl, Tbr 0x000077
7.1.2 L, R, C, LFE, Ls, Rs, Lb, Rb, TL, TR 0x0000CF
7.1.4 L, R, C, LFE, Ls, Rs, Lb, Rb, Tfl, Tfr, Tbl, Tbr 0x00007F