SECTION 9.1
763
Multimedia
KEY
TYPE
VALUE
SP
dictionary
(Optional)
A
media screen parameters
dictionary (see Section 9.1.5, “Media Screen
Default value: a media screen parameters dictionary whose entries (see Table 9.17)
all contain their default values.
Selector Renditions
A
selector rendition dictionary
specifies an array of rendition objects in its
R
entry
(see Table 9.7). The renditions in this array should be ordered by preference, with
the most preferred rendition first. At play-time, the renditions in the array are
evaluated and the first viable media rendition, if any, is played. If one of the rendi-
tions is itself a selector, that selector is evaluated in turn, yielding the equivalent
of a depth-first tree search. Note, however, that a selector rendition itself may be
non-viable; in this case, none of its associated media renditions are evaluated (in
effect, this branch of the tree is skipped).
This mechanism may be used, for example, to specify that a large video clip
should be used on high-bandwidth machines and a smaller clip should be used
on low-bandwidth machines.
TABLE 9.7 Additional entries specific to a selector rendition dictionary
KEY
TYPE
VALUE
R
array
(Required)
An array of rendition objects. The first viable media rendition object
found in the array, or nested within a selector rendition in the array, should be used.
An empty array is legal.
9.1.3 Media Clip Objects
There are two types of media clip objects, determined by the subtype
S
, which
can be either
MCD
for media clip data (see “Media Clip Data” on page 764) or
MCS
for media clip section (see “Media Clip Section” on page 767). The entries
common to all media clip dictionaries are listed in Table 9.8.