- From: Eric Hansen <ehansen7@hotmail.com>
- Date: Thu, 29 Jun 2000 02:55:11 EDT
- 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 ________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com
Received on Thursday, 29 June 2000 02:55:43 UTC