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CHAPTER 9                                                           Multimedia Features



If a non-viable media player info object is referenced by MU, NU, or A, it is treated
as if it were not present in its original array, and a media player info object con-
taining the same software identifier dictionary (see “Software Identifier Dictio-
nary” on page 779) is logically considered to be present in NU. The same rule
applies to a media player info object that contains a partially unrecognized soft-
ware identifier dictionary.

Since both media clip data and media play parameters dictionaries can be em-
ployed in a play operation, and each can reference a media players dictionary,
there is a potential for conflict between the contents of the two media players dic-
tionaries. At play-time, the viewer should use the following algorithm to deter-
mine whether a player present on the machine can be employed. The player
cannot be used if any of the following conditions are true:

Algorithm 9.1

   1.   The content type is known and the player does not support the type.
   2.   The player is found in the NU array of either dictionary.
   3.   Both dictionaries have non-empty MU arrays and the player is not found in both
        of them, or only one of the dictionaries has a non-empty MU array and the player
        is not found in it.
   4.   Neither dictionary has a non-empty MU array, the content type is not known, and
        the player is not found in the A array of either dictionary.

If none of the conditions are true, the player can be used.

Note: A player is “found” in the NU, MU, or A arrays if it matches the information
found in the PID entry of one of the entries, as described by Algorithm 9.2.

Media Player Info Dictionary

A media player info dictionary provides a variety of information regarding a spe-
cific media player. Its entries (see Table 9.26) allow information to be associated
with a particular version or range of versions of a player. As of PDF 1.5, only the
PID entry provides information about the player, as described in the next section,
“Software Identifier Dictionary”.

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