SECTION 9.1
767
Multimedia
•
If
BU
is not present and the media is embedded within the document, the URL
to the PDF file itself should be used as if it were the value of a
BU
entry in the
BE
dictionary; that is, as an implicit best-effort base URL.
TABLE 9.11 Entries in a media clip data MH/BE dictionary
KEY
TYPE
VALUE
BU
ASCII
string
(Optional)
An absolute URL to be used as the base URL in resolving any relative
URLs found within the media data.
Media Clip Section
A
media clip section
dictionary (see Table 9.12) defines a continuous section of
another media clip object (known as the
next-level
media clip object). For exam-
ple, a media clip section could define a 15-minute segment of a media clip data
object representing a two-hour movie. The next-level media clip object, specified
by the
D
entry, can be either a media clip data object or another media clip sec-
tion object. However, the linked list formed by the
D
entries of media clip sec-
tions must terminate in a media clip data object. If the next-level media object is
non-viable, the media clip section is also non-viable.
TABLE 9.12 Additional entries in a media clip section dictionary
KEY
TYPE
VALUE
D
dictionary
array
dictionary
dictionary
(Required)
The media clip section or media clip data object (the next-level media
object) of which this media clip section object defines a continuous section.
(Optional)
An array that provides alternate text descriptions for the media clip sec-
tion in case it cannot be played; see “Multi-language Text Arrays” on page 942.
(Optional)
A dictionary whose entries (see Table 9.13) must be honored for the me-
dia clip section to be considered viable.
(Optional)
A dictionary whose entries (see Table 9.13) need only be honored in a
“best effort” sense.
Alt
MH
BE
The
B
and
E
entries in the media clip section’s
MH
and
BE
dictionaries (see Table
D
by speci-
fying beginning and ending offsets into it. Depending on the media type, the off-
sets may be specified by time, frames, or markers (see “Media Offset Dictionary”
B
and
E
are not required to specify the same type of offset.