Signaling Dolby Digital Plus bitstreams with Dolby Atmos content in an ISO base media format file
In addition to the definitions in Annex F of ETSI TS 102 366, other information must be added to
the EC3SpecificBox in a backward-compatible way to describe the
characteristics of the Dolby Atmos content carried by a Dolby Digital
Plus
stream.
The extensions specific to audio objects are highlighted in the table. These extensions must be used to signal the presence of the Dolby Atmos content within an ISO base media file.
| Syntax | Word size in bits | Identifier |
|---|---|---|
EC3SpecificBox ()
|
|
|
{
|
|
|
BoxHeader.Size...................
|
32
|
uimsbf
|
BoxHeader.Type...................
|
32
|
uimsbf
|
data_rate........................
|
13
|
uimsbf
|
num_ind_sub......................
|
3
|
uimsbf
|
for (i = 0; i < num_ind_sub + 1; i++)
|
|
|
{
|
|
|
fscod........................
|
2
|
uimsbf
|
bsid.........................
|
5
|
uimsbf
|
reserved.....................
|
1
|
bslbf
|
asvc.........................
|
1
|
bslbf
|
bsmod........................
|
3
|
uimsbf
|
acmod........................
|
3
|
uimsbf
|
lfeon........................
|
1
|
bslbf
|
reserved.....................
|
3
|
uimsbf
|
num_dep_sub..................
|
4
|
uimsbf
|
if (num_dep_sub > 0)
|
|
|
{
|
|
|
chan_loc....................
|
9
|
uimsbf
|
}
|
||
else
|
|
|
{
|
|
|
reserved....................
|
1
|
bslbf
|
}
|
|
|
}
|
|
|
flag_ec3_extension_type_reserved.......
|
7
|
bslbf
|
flag_ec3_extension_type_a...............
|
1
|
bslbf
|
if (flag_ec3_extension_type_a == 1)
|
|
|
{
|
|
|
complexity_index_type_a..................
|
8
|
umisbf
|
}
|
|
|
additional_data[ ].......................
|
8
|
uimsbf
|
}
|
|
|
These extensions are Dolby Atmos related.
flag_ec3_extension_type_a
The one-bit field must be set to 1 to indicate that Dolby Atmos content is
carried in the first independent substream (I0) of a 5.1 Dolby Digital
Plus
stream.
flag_ec3_extension_type_reserved
This seven-bit field must be reserved for future application.
For content creation referring to this version of the specification, the reserved bits must be
set to 0. For playback referring to this version of the specification, the
reserved bits shall be ignored.
complexity_index_type_a
This eight-bit field indicates the decoding complexity of a Dolby Digital
Plus
bitstream carrying Dolby Atmos content. If the flag_ec3_extension_type_a bit in
the addbsi has a value of 0, the
complexity_index_type_a will not be available in the E-AC-3 descriptor. If
the flag_ec3_extension_type_a bit in the addbsi has a value
of 1, the complexity_index_type_a in the E-AC-3 descriptor
must take the value of the complexity_index_type_a field found in the
addbsi of the Dolby Digital
Plus bitstream.
A larger value indicates higher complexity.
additional_data[ ]
These optional bytes must be reserved for future use.
Other fields must conform to Annex F of ETSI TS 102 366.