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Re: TT and subtitling/captioning - separating timing from style from content - temporal flow of content

From: Al Gilman <asgilman@iamdigex.net>
Date: Thu, 07 Aug 2003 10:00:56 -0400
Message-Id: <5.1.0.14.2.20030807092647.02245170@pop.iamdigex.net>
To: Johnb@screen.subtitling.com, public-tt@w3.org

At 06:44 AM 2003-08-07, Johnb@screen.subtitling.com wrote:

>Dear TT-WG,
>
>For those that don't know me -  I am a software engineer for a company 
>that produces subtitling (captioning) equipment
>- so all my comments should be taken in that context.
>
>I have just been reading through the F2F minutes for March on the TT-WG 
>home page,
>and have two questions regarding the tentative model that seems to be 
>appearing for TT-AF.
>
>Assuming that I wish to separate the timing in my TT-AF document from the 
>content
>- by using references within the timing 'tree' a la Daisy model - and 
>assuming that this might be possible!
>- would it then possible to apply style through the timing tree rather 
>than by inline markup or attribute within the text content.

If you are happy to use a SMIL wrapper to sequence and time the presentation,
you can use the digital talking book specification and you don't need TT-AF
which will be a more lightweight specification for marking the timing in the
file with the text content, IIRC.

http://www.loc.gov/nls/niso/

Secondly, the best practice is not to apply the style inline in the timing
script, but it would be natural to associate a stylesheet cascade with each
channel or display region.  But you still want to put a well-articulated
display-mode-independent basis for the styling in the markup of the text 
itself.

http://www.w3.org/TR/xag
http://www.w3.org/TR/2000/NOTE-WCAG10-CSS-TECHS-20000920/

Why does the text have hard line breaks?  Typical cases are lists and poems.
The text markup should identify the list or poem and its sub-items the
stylesheet can then break the lines accordingly.

To indicate the rhetorical role of text subsets, use element types to the
fullest extent that they are defined to express this and class attribute
values for refinement beyond what can be expressed in the element typology.

Review the use of types and classes in the talking book DTDs for examples
of this good practices.


>I.e. - using example (crudely hatcheted from GA examples)
>
><seq>
><ref id="T27" dur="3s"/>
><ref id="T28" begin="T27.end " dur="3s"/>
></seq>
>
><tt:content id="T27">
>  Some text with some&nl; Hard line breaks.
></tt:content>
>
><tt:content id="T28">
>  Some more text with some&nl; Hard line breaks.
></tt:content>
>
>will it be possible to do something like this.... (in spirit if not in 
>exactly this manner...)?
>
><seq>
><ref id="T27" dur="3s" style="text-indent:10pt"/>
><ref id="T28" begin="T27.end " dur="3s" style="font-size:14pt"/>
></seq>
>
><tt:content id="T27">
>  Some text with some&nl; Hard line breaks.
></tt:content>
>
><tt:content id="T28">
>  Some more text with no Hard line breaks.
></tt:content>
>
>further - might it be possible to replace the style attribute above
>with a reference to an element (or portion of a style sheet)
>that defines the style (to avoid multiple large style attribute 
>definitions)? E.g.
>
><seq>
><ref id="T27" dur="3s" style="S1"/>
><ref id="T28" begin="T27.end " dur="3s" style="S2"/>
></seq>
>
><tt:content id="T27">
>  Some text with some&nl; Hard line breaks.
></tt:content>

CSS provides facilities to apply styles by ID-keyed selctors but this is
should be avoided.  Talk with someone else to help you articulate the
rationale for the style.  Then encode the basis for the styling decisions in
[elements and attributes in] the content markup, and key the result to the
encoded basis by the selector in your separate style rule.  This will give
you a rule you can lift and reuse.


><tt:content id="T28">
>  Some more text with no Hard line breaks.
></tt:content>
>
><StyleDef id="S1" defn="text-indent:10pt"/>
><StyleDef id="S2" defn="font-size:14pt"/>
>
>A second question....
>
>It would be desirable for TT (at least IMHO) to include mechanisms for 
>describing the temporal breaking of content.
>What I am thinking of is a document that does not describe explicitly the 
>timing for all of the content
>- but rather describes that X amount of content fits into a box of size Y 
>over a time period of Z.
>Now if the content X is too large for box Y - how does the content get 
>over(?)flowed in a 'temporal sense' through the box.
>
>This is a 'crux' issue in subtitling / captioning.

Yes, this is an important rendering decision.  However, a separated approach
would still put the rationale for the presentation decision in the content
markup, and key the presentation effect to this in a style rule as above.

Compare with the overflow-related properties in CSS3 box model.  String-search
for 'overflow' in

  CSS3 module: The box model
  http://www.w3.org/TR/css3-box/

What a text fragment between timing marks is played into is a box again,
just in screen-by-time and not just screenX-by-screenY.

By analogy with these properties we can come up with a
rendering-in-space-time processing model and allocate the encoding of the
necessary control information to TT-AF and separate style sheets in the
context of the elaborated processing requirements.

Al

>regards
>John Birch
>
>The views and opinions expressed are the author's own and do not necessarily
>reflect the views and opinions of Screen Subtitling Systems Limited.
Received on Thursday, 7 August 2003 15:00:20 GMT

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