SECTION 9.1
771
Multimedia
ration may be modified when a media clip section (see “Media Clip Section” on
gin and end offsets. For a media type having no notion of time (such as a JPEG
image), the duration is considered to be infinity.
If the simple duration is longer than the intrinsic duration, the player should
freeze the media in its final state until the simple duration has elapsed. For visual
media types, the last appearance (frame) would be displayed. For aural media
types, the media is logically frozen but should not continue to produce sound.
Note:
In this case, the
RC
entry, which specifies a repeat count, applies to the simple
duration; therefore, the entire play-pause sequence is repeated
RC
times.
TABLE 9.16 Entries in a media duration dictionary
KEY
TYPE
VALUE
Type
name
name
(Optional)
The type of PDF object that this dictionary describes; if present, must be
MediaDuration
for a media duration dictionary.
(Required)
The subtype of media duration dictionary. Valid values are:
I
F
T
S
The duration is the intrinsic duration of the associated media
The duration is infinity
The duration is specified by the
T
entry
The media duration dictionary is considered non-viable if the viewer application
does not recognize the value of this entry.
T
dictionary
(Required if the value of
S
is
T
; otherwise ignored)
A timespan dictionary specifying
an explicit duration (see Table 9.24). A negative duration is illegal.
9.1.5 Media Screen Parameters
A media screen parameters dictionary (see Table 9.17) specifies where a media
object should be played. It contains
MH
and
BE
dictionaries (see Table 9.18),
which function as discussed in Section 9.1.1, “Viability.” All media clips that are
being played are associated with a particular document and must be stopped
when the document is closed.
Note:
It is recommended that viewer applications disallow floating windows and
full-screen windows unless specifically allowed by the user. The reason is that docu-
ment-based security attacks are possible if windows containing arbitrary media con-
tent can be displayed without indicating to the user that the window is merely