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                                            788
CHAPTER 9                                                             Multimedia Features



Typically, images are stored in the document as image XObjects (see Section
4.8.4, “Image Dictionaries”), thereby allowing them to be shared between the
standard PDF representation and the slideshow. Other media objects are stored
or embedded file streams (see Section 3.10.3, “Embedded File Streams”). Also,
see Implementation note 156 in Appendix H.

To allow viewers to verify content against the supported features in a particular
viewer, it is a requirement that all referenced objects include a Type entry in their
dictionary, even when the Type entry is normally optional for a given object.

The following example illustrates the use of alternate presentation slideshows.

Example 9.1

   1 0 obj
       <</Type /Catalog
          /Pages 2 0 R
          /Names 3 0 R            % Indirect reference to name dictionary
       >>
   ...
   3 0 obj                         % The name dictionary
       <</AlternatePresentations 4 0 R >>
   endobj
   4 0 obj                        % The alternate presentations name tree
       <</Names [(MySlideShow) 5 0 R]>>
   endobj
   5 0 obj                        % The slideshow definition
       <</Type /SlideShow
          /Subtype /Embedded
          /Resources <</Names [ (mysvg.svg) 31 0R
              (abc0001.jpg) 35 0 R (abc0002.jpg) 36 0 R
              (mysvg.js) 61 0 R (mymusic.mp3) 65 0 R ]>>
          /StartResource (mysvg.svg)
       >>
   ...
   31 0 obj
       <</Type /Filespec          % The root object, which
          /F (mysvg.svg)          % points to an embedded file stream
          /EF <</F 32 0 R>>
       >>
   endobj
   32 0 obj                             % The embedded file stream
       <</Type /EmbeddedFile

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