HTTP Live Streaming playlist files with associated audio for receiver mixing
A single Dolby Digital Plus bitstream may include one or more associated audio programs in addition to the main audio program (program extensions).
For example, the associated audio program may be used to provide an audio description for the visually impaired or an audio presentation for the hearing impaired. The associated program is intended to be mixed with the main audio program after decoding. When providing content using these program extensions, we recommend providing the same content in all bandwidth variants.
If associated audio streaming is not always desired (for example, to provide different
versions for different clients), we recommend that a rendition group that contains
renditions with and without associated audio streams be made available. In a playlist,
alternative renditions of the same content are identified with the
#EXT-X-MEDIA
parameter. To properly signal Dolby Digital
Plus
renditions using the #EXT-X-MEDIA
parameter:
- Provide a meaningful
NAME
attribute (for example,Movie
for the rendition without an associated program orMovie with a spoken scene description
for the visually impaired for a rendition with an associated program).Receivers may display the
NAME
attribute value for manual user selection and use theDDP-PROGRAM1
,DDP-PROGRAM2
, andDDP-PROGRAM3
attribute values to enable automatic selection of alternative content (for example, for visually impaired users). - For a rendition that contains associated programs, indicate the
associated programs in the
<attribute-list>
of the#EXT-X-MEDIA
parameter:- Add the
DDP-PROGRAM0
attribute to the<attribute-list>
of the#EXT-X-MEDIA
parameter. TheDDP-PROGRAM0
attribute must indicate the eight-bit substream information with an unquoted hexadecimal integer number as specified in this table.Table 1. Dolby Digital Plus PROGRAM0 bits Dolby Digital Plus PROGRAM0 bits Description b7
(most-significant bit)Reserved (must be set to 1
)b6
Full_service_flag
b5
tob3
Service_type
b2
tob0
Number_of_channels
The substream information for the
DDP-PROGRAM0
attribute, listed in the table, is indicated in the same way as the comparable parameters of the E-AC-3 audio descriptor. (See the Semantics for the enhanced AC-3 descriptor section.) - If the Dolby Digital
Plus stream
contains an independent substream with a
substreamid
value of1
, add aDDP-PROGRAM1
attribute to the<attribute-list>
of the#EXT-X-MEDIA
parameter. - If the Dolby Digital
Plus stream
contains an independent substream with a
substreamid
value of2
, add aDDP-PROGRAM2
attribute to the<attribute-list>
of the#EXT-X-MEDIA
parameter. - If the Dolby Digital
Plus stream
contains an independent substream with a
substreamid
value of3
,DDP-PROGRAM3
attribute must be added to the<attribute-list>
of the#EXT-X-MEDIA
parameter.
library_booksNote: We recommend also adding aDDP-PROGRAM0
attribute to the<attribute-list>
of the#EXT-X-MEDIA
parameter for the rendition that does not contain an associated program. TheDDP-PROGRAM0
attribute describes the configuration of independent substream 0 (and, if present, any dependent substreams associated with independent substream 0) of the Dolby Digital Plus stream. - Add the
- The
DDP-PROGRAM1
,DDP-PROGRAM2
, andDDP-PROGRAM3
attributes must indicate the eight-bit substream information with an unquoted hexadecimal integer number as is also used in the E-AC-3 audio descriptor. (See Substream 1–3 field bit value assignments.)