Dolby Digital Plus bitstream structure
A Dolby Digital Plus bitstream is constructed from one or more substreams. Each substream is a sequence of frames that can carry up to 5.1 channels of audio.
The use of multiple substreams allows delivery of a single program with more than 5.1 channels, multiple independent programs, or a combination within a single Dolby Digital Plus bitstream. The substreams are time multiplexed. Section E.2.8 of ETSI TS 102 366 provides detailed information on the use and structure of multiple substreams within a Dolby Digital Plus bitstream.
The frames that make up each substream are constructed from smaller units called blocks, each representing 256 samples of audio from each channel carried in the substream. A frame may contain one, two, three, or six blocks of audio data (representing 256, 512, 768, or 1,536 samples of PCM audio).
If Dolby Atmos content is present in a Dolby Digital
Plus bitstream, the
addbsi field includes extensions specific to Dolby Atmos in the first
independent substream (I0) of a 5.1-channel Dolby Digital
Plus bitstream. The
complexity_index_type_a field takes a value of 1 to
16 that indicates the decoding complexity of the Dolby Atmos bitstream. The
syntax is shown in this table.
| Syntax | Word size in bits | Identifier | Value | |
|---|---|---|---|---|
addbsie
|
1
|
|||
addbsil
|
1
|
|||
addbsi
includes: |
flag_ec3_extension_type_reserved
|
7
|
bslbf
|
0
|
flag_ec3_extension_type_a
|
1
|
bslbf
|
1
|
|
complexity_index_type_a
|
8
|
uimsbf
|
1 － 16
|