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RE: Timed Text Authoring Format - Distribution Format Exchange Pr ofile (DFXP)

From: Glenn A. Adams <gadams@xfsi.com>
Date: Thu, 17 Mar 2005 11:20:04 -0500
Message-ID: <7249D02C4D2DFD4D80F2E040E8CAF37C03C353@longxuyen.xfsi.com>
To: <Johnb@screen.subtitling.com>, <public-tt@w3.org>
 

 

  _____  

From: Johnb@screen.subtitling.com [mailto:Johnb@screen.subtitling.com] 
Sent: Thursday, March 17, 2005 11:01 AM
To: public-tt@w3.org
Subject: RE: Timed Text Authoring Format - Distribution Format Exchange
Pr ofile (DFXP)

 

Glenn,

 

Just to bottom this thread....

 

The timing attributes were added to <tt/> to support timing on <set/>
children of <region/> whose ancestors are <layout/>, <head/>, then
<tt/>.

 

 

I'm not exactly sure what you can do with timing in both the body and tt
elements that cannot be achieved just in thebody element, but it was
more of a question than an issue.... 

 

[GA] For one thing, you can express that <tt/> is a par timing
container, and that <body/> is a seq timing container. You can also
express that <tt/> establishes a larger timing window than <body/>,
e.g., have a 2 hour duration for <tt/> but a 30 min duration for <body/>
starting at some offset.

 

As regards the mixed alignment line, it is an uncommon scenario (though
not as uncommon as might be thought - since saving space is often an
issue in subtitling). I guess XSL-FO is bound by preconceptions of the
web-page as output - since, as you identify, support for such features
exists in print oriented languages. 

 

Can the fo:inline-container object be used to support the mixed
alignment line concept?

 

[GA] No.

 

In the absence of the ability to set text-alignment on a span, I think
**my** most likely DFXP implementation of this behaviour would be to
create a transparent region for the right aligned section and overlay
it. This does however mean that explicit line breaks and careful
authoring would be required, since otherwise collision would be almost
certain to occur.

 

[GA] The group already had discussed this matter in the past and had
settled on this approach (overlaying regions) if one really wanted to do
this.

 

BTW - a conversion of DFXP into XSL-FO is a good validation of DFXP -
but I would suggest that most practical conversions will be direct to
the target distribution format. I.e. for me...  DFXP to Teletext, or
DFXP to Line21.

 

[GA] Conversion from DFXP into XSL-FO is not mandated by DFXP; rather,
the possibility of such a mapping is mandated (subject to certain
extensions) in order to formalize the DFXP formatting/layout semantics
model. The alternative would be that DFXP would have to fully specify a
format/layout semantics model such as the CSS Box model or the XSL Area
model. The WG felt that we should reuse as many existing W3C
specifications as possible rather than re-inventing; as a consequence,
we evaluated the use of both CSS and XSL FO models, and adopted the XSL
FO model as our semantics, primarily based upon our perception that XSL
FO had done a better job of formalizing layout and folding in
internationalization support (note that much of this has also been
adopted in subsequent CSS Level 3 work, but has not yet been promoted to
REC; we preferred to work with XSL FO partly because it is finalized as
a REC).

 

best regards John Birch.

	-----Original Message-----
	From: Glenn A. Adams [mailto:gadams@xfsi.com]
	Sent: 17 March 2005 13:53
	To: Johnb@screen.subtitling.com
	Cc: public-tt@w3.org
	Subject: RE: Timed Text Authoring Format - Distribution Format
Exchange Pr ofile (DFXP)

	 

	 

	
  _____  


	From: Johnb@screen.subtitling.com
[mailto:Johnb@screen.subtitling.com] 
	Sent: Thursday, March 17, 2005 6:37 AM
	To: Glenn A. Adams
	Cc: public-tt@w3.org
	Subject: RE: Timed Text Authoring Format - Distribution Format
Exchange Pr ofile (DFXP)

	 

	Glenn,

	 

	Thanks for the speedy reply - some more comments inline :-)

	 

	best regards

	 

	John Birch

		-----Original Message-----
		From: Glenn A. Adams [mailto:gadams@xfsi.com]
		Sent: 16 March 2005 17:55
		To: Johnb@screen.subtitling.com
		Cc: public-tt@w3.org
		Subject: RE: Timed Text Authoring Format - Distribution
Format Exchange Pr ofile (DFXP)

		 

		7.1.1 tt

		If begin and (or) end attributes are specified on the tt
element, then they specify the beginning and (or) ending points of a
time interval for a document instance in relationship with some external
application or presentation context. The temporal begin and end points
determined by an external application or presentation are referred to
subsequently as the external time interval.

		Is it necessary to have begin and (or) end attributes
for both the tt element and the body element? Could this be simplified
so that begin and (or) end is only specified on the tt element?

		 

		No. Neither is required. Is there something in the text
that led you to infer that both were required? 

		 

		Ahhh.... I didn't make myself clear.... What I meant to
say was.... does the DXFP  specification need to support a begin / end
attribute on both the tt element and the body element? Would it be
possible to simplify the DXFP **specification** by removing timing
attributes from one of these elements, since I cannot see any situation
that requires both elements to have timing attributes. IMHO a document
using timing attributes on both tt and body can be **equivalently**
represented by a single set of timing attributes on just one of these
elements. Am I missing something? What is gained by having timing
attributes at both levels in the document hierarchy, given that both tt
and body can only occur once in a document instance?

		 

		The timing attributes were added to <tt/> to support
timing on <set/> children of <region/> whose ancestors are <layout/>,
<head/>, then <tt/>.

		 

		8.2.19 tts:textAlign

		 

		Applies to:        p

		 

		Can we allow tts:textAlign to apply to span as well.
Otherwise, I don't believe it is possible to have:

		 

Hello?

 

Come In!

Please have a seat

		 

		 

		No. You cannot do this in a single paragraph. You would
have to overlay two regions on top of one another and have one of them
use a transparent background.  

		 

		A bit ugly - and prone to problems with text collisions
which I would hope to avoid! Imagine if the second phrase were modified
to read "Come In! I've been waiting to meet you."

		 

		Text alignment (in the inline progression dimension)
applies to the positioning of line areas within a block area. A text
alignment on a span would always pertain individually to each inline
area produced by the span, and since each such inline area is bounded by
glyph areas at both start and end edges, there would be no extra room in
which to move those glyph areas within the inline area.

		 

		Is there no way to createan inline block area that fills
to the end of the line (region)? I am assuming that the DXFP for the
above would be:

		 

		<p id="subtitle5" begin="10:00:00:00" end="10:00:05:00"
style="rightaligned">

		<span tts:textAlign="left">

		Hello?

		</span>

		<span begin="10:00:02:00">

		Come In!</br>Please have a seat

		</span>

		</p> 

		 

		Or:

		 

		 

		<p id="subtitle5" begin="10:00:00:00" end="10:00:05:00"
style="rightaligned">

		<span tts:textAlign="left">

		Hello?

		</span>

		 

		<span begin="2:00">

		Come In!

		</br>

		</span>

		</p> 

		<p id="subtitle 6 " begin="10:00:02:00"
end="10:00:05:00" style="rightaligned">

		Please have a seat

		</p> 

		 

		 

		So why can the first span not create an inline area that
is left aligned within the region and contains the text Hello?,
terminating in area just after the ? When the second span activates -
can the inline area generated not stretch from the previous inline area
until the end of the line - there is an explicit break in the first
example and an implicit break in the second?

		 

		We base our basic formatting/layout semantics on XSL
1.0, which does not support text-align on inline-level formatting
objects. The closest feature in XSL that would support this would be the
use of inline margins, e.g.,

		 

		<fo:block text-align="end">

		<fo:inline>Hello?</fo:inline>

		<fo:inline space-start.minimum="0px"
space-start.maximum="200px" space-start.opt="200px">Come In!</fo:inline>

		<fo:character character="&#x000A;"/>

		<fo:inline space-start.minimum="0px"
space-start.maximum="200px" space-start.opt="200px">Please have a
seat</fo:inline>

		</fo:block>

		 

		Supporting this in DFXP would require introducing an
equivalent of the space-* properties of XSL, which involves a level of
complexity that may not be appropriate for this profile (and will
certainly require discussion by the WG).

		 

		If I were using TeX, I would handle by inserting an
\hskip or \hfil command possibly with a \penalty command before or after
to adjust line break precedence rules.

		 

		Another, but more complex means for handling this would
be to introduce a construct or mechanism that works similar to TAB in
traditional word processors.  

		 

		Ugghhhh! Really really Ugghhhh! 

		I am not sure how you could use a tab construct, you
would need to position the tab by knowing how long the rendered second
phrase (the right aligned part) was - since the right aligned part would
actually be left aligned to the tab. 

		 

		Another way to handle, but using a simpler, yet manual
approach, would be to use multiple non-breaking spaces before "Come" and
"Please". 

		 

		Ugghhhh!

		Thisapproach would not work for regions that were
specified with relative (proportionate) sizes and would not achieve the
same results for different font sizes (or indeed fonts). Admittedly,
this is how the above effect is currently achieved though!

		 

		I suspect this is what you will end up doing in DFXP as
well.

		 

		Regards,

		Glenn

		 

		 

		
  _____  


		From: Johnb@screen.subtitling.com
[mailto:Johnb@screen.subtitling.com] 
		Sent: Wednesday, March 16, 2005 10:48 AM
		To: public-tt@w3.org
		Subject: RE: Timed Text Authoring Format - Distribution
Format Exchange Pr ofile (DFXP)

		 

		Glenn, et al, 

		I have a number of minor comments / questions regarding
the draft that I have placed in the attached Word document. Apologies
for using this format but it allows me to easily illustrate certain
points regarding formatting without generating images.

		I have a couple of other points that I will make in
separate emails. 

		with best regards 
		John Birch. 

		 

		-----Original Message----- 
		From: Glenn A. Adams [mailto:gadams@xfsi.com] 
		Sent: 14 March 2005 16:51 
		To: public-tt@w3.org 
		Subject: Timed Text Authoring Format - Distribution
Format Exchange 
		Profile (DFXP) 

		 

		A new update of the Timed Text Authoring Format 1.0 -
Distribution 
		Format Exchange Profile (DFXP), is now available at [1]:


		http://www.w3.org/TR/2005/WD-ttaf1-dfxp-20050314/ 

		The TT WG solicits your comments on this new draft as
soon as possible, 
		as a very rapid turn-around is expected in order to
publish a first Last 
		Call (LC) draft. 

		Please sent comments either to this list or, if you
prefer privacy, to 
		me directly. 

		Regards, 
		Glenn Adams 

		 

		  
Received on Thursday, 17 March 2005 16:20:04 GMT

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