RE: TTML / tts:showBackground='always'

Dear Glenn,

            thanks, it is clear now. This is the point I was missing.
Best regards,
Sylvain

De : Glenn Adams [mailto:glenn@skynav.com]
Envoyé : mercredi 7 décembre 2016 19:43
À : KERVADEC Sylvain IMT/OLPS
Cc : Nigel Megitt; public-tt@w3.org
Objet : Re: TTML / tts:showBackground='always'

To be clear, I should add that, if no timing appears on region, then regions are always temporally active in TTML1; therefore, if showBackground is always, then you are correct that a region would be displayed regardless of whether content is selected into the region. Note, however, that if a region has a transparent background, then there would be no visible marks.

You will need to specify whenVisible on showBackground to avoid this situation. In TTML2, one could simply specify

<initial tts:showBackground="whenActive"/>

to change the initial value, but you don't have this option in TTML1/IMSC1.


On Wed, Dec 7, 2016 at 11:05 AM, Glenn Adams <glenn@skynav.com<mailto:glenn@skynav.com>> wrote:


On Wed, Dec 7, 2016 at 7:24 AM, <sylvain.kervadec@orange.com<mailto:sylvain.kervadec@orange.com>> wrote:
Dear Nigel,

            Thanks for your feedback.
This errata however clarifies the ‘whenActive’ case, but my misunderstanding concerns the ‘always’ case.

It may come from my wrong interpretation of what is a “Temporally Active Region”.
In my example, only the content elements carry timing attributes (‘begin’ and ‘end’). My understanding is that a region is a temporally active region when a temporally active content element is associated with it. Temporally inactive regions are thus not displayed, whatever the value of tts:showBackground.

Regions are also timed and can take begin/end/dur. See also [1] and [2], particularly:

> To the extent that time semantics apply to the content of the layout element, the implied time interval of this element is defined to be coterminous with the Root Temporal Extent.
[1] https://www.w3.org/TR/ttaf1-dfxp/#layout-vocabulary-region

[2] https://www.w3.org/TR/ttaf1-dfxp/#layout-vocabulary-layout



But for example, if a region has to be considered as temporally active during the entire life of the document, then the tts:showBackground value has to be evaluated and rendered, even when no content element associated with this region is temporally active.

IMSC1 prohibits overlapping presented regions. My example would thus be allowed or prohibited depending on the answer (Actually, it breaks IMSC1 compatibility on other features).

Best regards,
Sylvain.


De : Nigel Megitt [mailto:nigel.megitt@bbc.co.uk<mailto:nigel.megitt@bbc.co.uk>]
Envoyé : mercredi 7 décembre 2016 12:27
À : KERVADEC Sylvain IMT/OLPS; public-tt@w3.org<mailto:public-tt@w3.org>
Objet : Re: TTML / tts:showBackground='always'

Dear Sylvain,

Please could you read the errata to TTML1 at https://www.w3.org/2013/09/ttml1-errata.html#errata-8.2.17-1 and see if it answers your question?

For ease of reference, that section is:

[[

Correction in TTML1 Section 8.2.17 - tts:showBackground attribute<http://www.w3.org/TR/2013/REC-ttml1-20130924/#style-attribute-showBackground> (published 2014-07-31)

Description:
Clarify meaning of whenActive.

Resolution:

Add the following paragraph immediately prior to the paragraph starting with "If a computed value of the property ...":

A region satisfies the whenActive case if (1) it is a Temporally Active Region and (2) content is selected into the region, where that content is also Temporally Active.

________________________________
]]

Kind regards,

Nigel


From: "sylvain.kervadec@orange.com<mailto:sylvain.kervadec@orange.com>" <sylvain.kervadec@orange.com<mailto:sylvain.kervadec@orange.com>>
Date: Wednesday, 7 December 2016 at 09:41
To: "public-tt@w3.org<mailto:public-tt@w3.org>" <public-tt@w3.org<mailto:public-tt@w3.org>>
Subject: TTML / tts:showBackground='always'
Resent-From: <public-tt@w3.org<mailto:public-tt@w3.org>>
Resent-Date: Wednesday, 7 December 2016 at 09:43

Dear tt experts,

            I am looking for some clarifications on the expected behavior of the tts:showBackground parameter defined on a temporally inactive region.
To be more specific, I would like to know if the background of a temporally inactive region with a tts:showBackground equal to ‘always’ shall be displayed or not.
The topic has already been discussed (https://www.w3.org/AudioVideo/TT/tracker/issues/314, and 313, 330), but I still don’t know what is the correct answer.

I am using TTML2 as a reference, as it introduces some missing definitions on active regions:
The tts:showBackground definition says that “the background color of a region is always rendered when performing presentation processing on a visual medium”, when its value is equal to ‘always’.
However, the text also says “For the purpose of determining the semantics of presentation processing, a region that is temporally inactive must not produce any visible marks when presented on a visual medium.”
Reading IMSC1, “A presented region is a temporally active region that satisfies the following conditions:..” seems to indicate that an inactive region shall not be presented.

My understanding is thus that an inactive region shall not be displayed, whatever the value of tts:showBackground, but I would appreciate your guidance on the topic.

Here is an example:

<?xml version="1.0" encoding="UTF-8"?>
<tt xml:lang="fre" xmlns="http://www.w3.org/2006/10/ttaf1" xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter" xmlns:tts="http://www.w3.org/2006/10/ttaf1#styling" ttp:cellResolution="50 30">
   <head>
      <styling>
         <style xml:id="ts0" tts:fontFamily="monospaceSansSerif" tts:lineHeight="1c" tts:textDecoration="none" tts:fontWeight="normal" tts:fontStyle="normal" tts:fontSize="1c 1c" tts:color="#FFFFFFFF" tts:backgroundColor="#00000064" tts:textOutline="#000000FF 0.1c 0c"/>
         <style xml:id="ts1" tts:lineHeight="2c" tts:textDecoration="none" tts:fontWeight="normal" tts:fontStyle="normal" tts:fontSize="1c 2c" tts:color="#FFFFFFFF" tts:backgroundColor="#00000064" tts:textOutline="#000000FF 0.1c 0c"/>
         <style xml:id="ps0" tts:textAlign="center"/>
      </styling>
      <layout>
         <region xml:id="r0" tts:origin="10% 73%" tts:extent="80% 17%" tts:displayAlign="before"/>
         <region xml:id="r1" tts:origin="10% 66%" tts:extent="80% 24%" tts:displayAlign="before"/>
      </layout>
   </head>
   <body>
      <div style="ts0">
         <p region="r0" begin="00:00:00.280" end="00:00:01.640" style="ps0">
            <span style="ts1" xml:space="preserve">extirpé ?</span>
         </p>
         <p region="r0" begin="00:00:02.720" end="00:00:04.840" style="ps0">
            <span style="ts1" xml:space="preserve">Je dois dire que...</span>
         </p>
         <p region="r0" begin="00:00:07.880" end="00:00:09.960" style="ps0">
            <span style="ts1" xml:space="preserve">mes yeux sont verts, en fait.</span>
         </p>
         <p region="r1" begin="00:00:11.360" end="00:00:11.360" style="ps0">
            <span style="ts1" xml:space="preserve">Je ne qualifierais pas</span>
         </p>
         <p region="r1" begin="00:00:11.360" end="00:00:13.280" style="ps0">
            <span style="ts1" xml:space="preserve">Je ne qualifierais pas</span>
            <br/>
            <span style="ts1" xml:space="preserve">notre réticence</span>
         </p>
      </div>
   </body>
</tt>

The tts:showBackground defaults to ‘always’.
Two overlapping regions are defined (for single-line and two-lines subtitles), only one being active at any time.
If we have to display the background for inactive regions, it does not look good, as we have two semi-transparent regions on top of each other.
Adding tts:showBackground=’whenActive’ would solve our problem, but our contents have been generated without any tts:showBackground value so far.


Thanks in advance for your help.
Best regards,
Sylvain




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