CHAPTER 9
758
Multimedia Features
The following rules apply to the entries in
MH
and
BE
dictionaries, which behave
somewhat differently from other PDF dictionaries:
•
If an entry is required, the requirement is met if the entry is present in either
the
MH
dictionary or the
BE
dictionary.
•
If an optional entry is not present in either dictionary, it is considered to be
present with its default value (if one is defined) in the
BE
dictionary.
•
If an instance of the same entry is present in both
MH
and
BE
, the instance in
the
BE
dictionary is ignored unless otherwise specified.
•
If the value of an entry in an
MH
or a
BE
dictionary is a dictionary or array, it is
treated as an atomic unit when determining viability. That is, all entries within
the dictionary or array must be honored for the containing object to be viable.
Note:
When determining whether entries can be honored, it is not required that
each one be evaluated independently, since they may be dependent on one another.
That is, a viewer application or player may examine multiple entries at once (even
within different dictionaries) to determine whether their values can be honored.
The following media objects have
MH
and
BE
dictionaries. They function as de-
scribed above, except where noted in the individual sections:
•
Rendition (Table 9.2)
•
Media clip data (Table 9.11)
•
Media clip section (Table 9.13)
•
Media play parameters (Table 9.15)
•
Media screen parameters (Table 9.18)
9.1.2 Renditions
There are two types of
rendition
objects:
•
A
media rendition
(see “Media Renditions” on page 762) is a basic media object
that specifies what to play, how to play it, and where to play it.
•
A
selector rendition
(see “Selector Renditions” on page 763) contains an ordered
list of renditions. This list may include other selector renditions, resulting in a
tree whose leaves are media renditions. The viewer application should play the
first viable media rendition it encounters in the tree (see Section 9.1.1, “Viabili-