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Thoughts on multimedia and some definitions (Eric Hansen Comments)

From: Eric Hansen <ehansen7@hotmail.com>
Date: Thu, 29 Jun 2000 02:55:11 EDT
Message-ID: <20000629065511.83081.qmail@hotmail.com>
To: w3c-wai-ua@w3.org
To: UA List
From: Eric Hansen
Date: 29 June 2000
Subject: Thoughts on multimedia and some definitions (Eric Hansen Comments)

Ian's summary of the conversation between Ian, Charles, and Eric seems 
accurate.

Following are a few comments marked "<<EH>>".

See my other memo for today regarding my preferred definitions.

Ian wrote:
=======
   Questions:

     - To what extent is a multimedia presentation required
       to change over time? For instance, is a static HTML
       page with background audio playing a "degenerate"
       multimedia presentation?

     - Does a multimedia presentation necessarily require
       the synchronization of components? What if I have
       a page of images, I select a link to play an
       audio clip, and I select another link to view a
       video clip. Is this a multimedia presentation?

<<EH: My current answer is, yes, both of this can be. It is the Web author 
who determines whether model as a single multimedia presentation or as a 
bunch of smaller elements. The over-riding principle is preservation of 
function. The Web content developer is required to do whatever it takes to 
preserve the communication (message) function of the page when rendered in 
as an auditorially, visually, and tactually. He or she can parse an 
multimedia presentation into constituent uni-media presentations but he/she 
still has to communicate the message. The developer of user agents is to 
support the user by rendering content accessibly. …Here is a riddle: What is 
a very close relative of the collated text transcript? Answer: An accessible 
(e.g., text-only) alternative page. We need to talk more about collated text 
transcripts. This relates to Jon's comments on checkpoint 2.3 as cited by 
you in memo #0526.html in this series..>>

2) Stand-alone versus complementary. When an author produces
   content, some components may serve complementary purposes
   while others may serve equivalent purposes. For instance,
   in a television program, while the visual information and
   auditory information are certainly related, they are not
   equivalents for one another. Recall that an auditory
   equivalent for the visual track of a presentation is an
   audio track plus a synchronized auditory description of the
   visual information. <<EH: I think that it is more accurate to say that 
the auditory description is the auditory equivalent of the visual (or 
perhaps more accurately (?) -- the "non-auditory") tracks of the 
presentation. Also the word synchronized is misleading, since auditory 
descriptions are already synchronized.>>

   Other components of content may be (functional) equivalents
   of on another (e.g., text captions are the text equivalent
   of the audio track).

   It might be possible to define a multimedia presentation as:
       a) A presentation that includes both visual tracks and
          audio tracks.
       b) These tracks complement each other.
<<EH: See my other memo. This definition seems close but not quite broad 
enough.>>

   A stand-alone presentation is one that does not require
   a complement to convey its message. For instance, a radio
   program is a stand-alone auditory presentation.

   Based on these definitions, a radio program would not be
   consider a multimedia presentation, even if the radio
   program were accompanied by equivalents.

   Similarly, a radio program with an accompanying video
   track of signing hands would not be a multimedia presentation
   since the visual track is a functional equivalent of the
   audio. Alternatives form a unit in a different way than
   multimedia components form a unit. I think it's possible
   to talk about "primary content" and its alternatives as
   a unit. "Primary" probably means what the author intends
   to be rendered most of the time.
<<EH: I am thinking that we have an urgent need to reach consensus on the 
meanings of primary and alternative content, if those are to be the 
contrasting terms.>>

3) Presentation versus Track

   a) Based on the previous discussion of "complementary"
      components, the term presentation would refer to
      a "complete" presentation (all necessary components
      included, be they stand-alone or multimedia, with
      alternative equivalents considered separately).

   b) The term "track" would refer to either a video or
      and audio track of a multimedia presentation. However,
      if a static HTML page plus background audio is considered
      a multimedia presentation, then calling the static page
      a "track" seems odd. Calling the background audio a
      track seems less odd to me. <<EH: I understand the feeling but I think 
that the definition of track needs to be broad and flexible as does the 
definition of multimedia.>>

   c) With some formats, user agents can distinguish tracks,
      with others, they may not be able to (e.g., a SMIL
      presentation with discernible tracks versus a single
      mixed audio source).


Proposal:

1) Start with basic components in terms of rendering, not
   source format:

  <DEF>
   Visually rendered content: any content rendered for the
     visual sense. This would have to include images, text,
     video, scripts that produce visual effects, style sheets
     that produce visual effects, etc.
  </DEF>

  <DEF>
   auditorily rendered content: any content rendered for the
     visual  <<EH: Should read "auditory">> sense. This includes text 
rendered as
     speech, pre-recorded audio, etc.
  </DEF>

2) Introduce stand-alone v. track:

  <DEF>
   Stand-alone audio presentation: Auditorily rendered
   dynamic content that conveys a message without
   requiring additional content. Note that stand-alone
   audio presentations require alternatives
   so that they will be accessible to some users.
  </DEF>
<<EH: Like Al, I have concern about the word "dynamic">>

  <DEF>
   Stand-alone video presentation: Visually rendered
   dynamic content that conveys a message without
   requiring additional content. Note that stand-alone
   video presentations require alternatives
   so that they will be accessible to some users.
  </DEF>

  <DEF>
   Auditory track: Auditorily rendered dynamic content
   that is functionally part of a larger presentation.
   Note that audio tracks require alternatives
   so that they will be accessible to some users.
  </DEF>

  <DEF>
   Visual track: visually rendered dynamic content
   that is functionally part of a larger presentation.
   Note that visual tracks require alternatives
   so that they will be accessible to some users.
  </DEF>

  <DEF>
   Synchronized multimedia presentation: A presentation
   consisting of at least one auditory track that is
   synchronized with a visual track. Note that tracks
   of a multimedia presentation require alternatives so
   that they will be accessible to some users.
  </DEF>


Notes and questions;

  - Where does animation fit? <<EH: It is either a standalone visual 
track&&&

  - The term "dynamic content" needs to be clarified.

  - Part of the discussion involved trying to fit static
    content plus background audio into a larger definition.
    Trying to do so may be a mistake. At the 22 June
    teleconference [5], Gregory took an action item to
    investigate requirements for configuring the user
    agent to not render audio on load, so I anticipate
    the background audio question to be resolved in
    light of Gregory's proposals.

  - When should we use "audio" and when should we use
    "auditory"? Same for "video" and "visual". Also, we
    have consciously used the term "graphical" instead
    of "visual" for a long time.

[5] http://lists.w3.org/Archives/Public/w3c-wai-ua/2000AprJun/0505.html


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Received on Thursday, 29 June 2000 02:55:43 GMT

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