W3C home > Mailing lists > Public > public-tt@w3.org > December 2016

Re: TTML / tts:showBackground='always'

From: Nigel Megitt <nigel.megitt@bbc.co.uk>
Date: Wed, 7 Dec 2016 11:27:20 +0000
To: "sylvain.kervadec@orange.com" <sylvain.kervadec@orange.com>, "public-tt@w3.org" <public-tt@w3.org>
Message-ID: <D46DA244.32004%nigel.megitt@bbc.co.uk>
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)


Clarify meaning of whenActive.


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,


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">
         <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"/>
         <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"/>
      <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 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 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 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 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>
            <span style="ts1" xml:space="preserve">notre réticence</span>

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,


Ce message et ses pieces jointes peuvent contenir des informations confidentielles ou privilegiees et ne doivent donc
pas etre diffuses, exploites ou copies sans autorisation. Si vous avez recu ce message par erreur, veuillez le signaler
a l'expediteur et le detruire ainsi que les pieces jointes. Les messages electroniques etant susceptibles d'alteration,
Orange decline toute responsabilite si ce message a ete altere, deforme ou falsifie. Merci.

This message and its attachments may contain confidential or privileged information that may be protected by law;
they should not be distributed, used or copied without authorisation.
If you have received this email in error, please notify the sender and delete this message and its attachments.
As emails may be altered, Orange is not liable for messages that have been modified, changed or falsified.
Thank you.
Received on Wednesday, 7 December 2016 11:27:53 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 17:44:04 UTC