Media Equivalents

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The PDF Reference

Where Found:  9.1, Multimedia (pp. 711->; 9.1.2, Renditions (pp.715-737);Appendix H - Compatibility and Implementation Notes" of the PDF Reference 1.6.

Key Text: (if any):  TBD

To be discussed

• I have taken the tack that guidance on using accessibility features (alternate languages; visual captioning; minimum screen size; etc.) should not be in the specification, but relegated to  informative guidance to the author. This is a departure from the WCAG 2.0 approach I followed.
  
• Should we allow authors to use  1.6 PDF reference specification features that the current Acrobat reader version does not implement? (see Appendix H - Compatibility and Implementation Notes) I recommend yes. One way is to specify that things "should" be done according to the recommendations but not prohibit things possible under the PDF 1.6 reference.
  

Proposed Text

1. Multimedia objects may be embedded within accessible PDF files.
2. Embedded multimedia objects should be in one of the media formats (e.g., common MIME types) identified in "Appendix H - Compatibility and Implementation Notes" of the PDF Reference 1.6.
   
3. Multimedia objects or Media objects (e.g., graphics, Xobjects, inline images) essential to the author's intent shall contain an alternate description as a structure element entry. This description shall usually be implemented as an "Alt" entry but may be implemented as an "ActualText" entry under qualifying circumstances.
   
4. The multimedia object or media object within the document may contain an alternate description that identifies the source of the multimedia or the source of alternate forms of the object that could be more accessible to some users. This description shall usually be implemented as an "Alt" entry but may be implemented as an "ActualText" entry under qualifying circumstances.
5. The document may contain multiple renditions of other presentations of content that could be more accessible to some users.
   

Issues to take forward to Implementation 

1. Determine whether we need to address how PDF 1.5 addresses these technical issues.  My assumption is that we need only to address PDF 1.6 capabilities in the draft. PDF 1.6 looks relatively clear to me how user agents can access and negotiate among several available renditions.
2. Does anyone use Optional Content (Section 4.10) as a means to provide alternative content to suit user's needs?
   

Suggested changes, additions (by those other than the page initiator)

• Ideas, questions or concerns
• xxx