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                                                        763
           SECTION 9.1                                                                      Multimedia



KEY           TYPE            VALUE

SP            dictionary      (Optional) A media screen parameters dictionary (see Section 9.1.5, “Media Screen
                              Parameters”) that specifies where the media rendition object should be played.
                              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.

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