Timed Text Working Group Teleconference

04 Dec 2014

See also: IRC log


glenn, pal, Thierry, Andreas, nigel, jdsmith, mike, courtney


<trackbot> Date: 04 December 2014

<scribe> scribeNick: nigel

This meeting

nigel: is there AOB?
... We should mention the ITU-R WP6B liaison

IMSC 1 transition to CR

nigel: Pierre and I met the Director and plh and Thierry yesterday to discuss transition of IMSC 1 to CR.
... [result not minuted]


<trackbot> action-333 -- Pierre-Anthony Lemieux to Create a one pager to cover the plan for the director's meeting for taking imsc1 to cr. -- due 2014-11-27 -- PENDINGREVIEW

<trackbot> http://www.w3.org/AudioVideo/TT/tracker/actions/333

close action-333

<trackbot> Closed action-333.

tmichel: The document will be published on Dec 9 and then I'll send the call for implementation announcement
... on the same day. It will also be advertised on the W3C homepage.
... The webmaster has approved the document today.
... (so it is now frozen)

nigel and pal: Thanks everyone for the work put into this document.

glenn: Congratulations.

pal: The next step is to start compiling our test suite and test material. I plan to translate the DECE
... submission into what I think is valid IMSC 1 documents - primarily a change to namespace.
... Also I'm going to reach out to implementors. Would the group also be interested in a more formal
... message or template message to send to those who are interested. How do we proceed?

tmichel: The Call for Implementations is sent out to the chairs and ac-forum and will be published on the W3C homepage.
... That will be done on the day of publication. We can take that message and send it to whomever we want.
... We need to wait until publication.

pal: Does that make it easy for people who want to contribute to know who to contact?

tmichel: I'll send a link. Basically it says the spec is now in CR and invites participation for implementation.
... It also says how to feedback to the public mailing list.

pal: Thank you. Also there are Simon's outstanding comments that have been deferred. Can we discuss that
... next week?

nigel: Okay.

Action Items


<trackbot> action-356 -- Nigel Megitt to Request review of ttml2 pending review issues from group -- due 2014-12-04 -- PENDINGREVIEW

<trackbot> http://www.w3.org/AudioVideo/TT/tracker/actions/356

close action-356

<trackbot> Closed action-356.

nigel: I should list the issues that have been implemented since last week, for review on 18th December,
... a similar timescale.

glenn: The list is: 21, 213, 236, 237, 285, 286, 294. Those are all the new ones since last week.


<trackbot> action-355 -- Glenn Adams to Resolve duplication between issue-357 and issue-229 -- due 2014-12-04 -- OPEN

<trackbot> http://www.w3.org/AudioVideo/TT/tracker/actions/355

glenn: I've been focusing on the issues so I've not done work on this AI or any of the others.


<trackbot> action-354 -- Mike Dolan to Investigate formal contact at arib -- due 2014-11-27 -- OPEN

<trackbot> http://www.w3.org/AudioVideo/TT/tracker/actions/354

mike: Status is: I reached out to the executive director of ARIB and he's going to get back to me.
... Somewhat unrelated, a colleague from Toshiba indicated some other practical aspects of the ARIB work
... so that's interesting too. It looks like another 6 months to a year before it's out for basic UHDTV.
... Hopefully before the holidays we'll have specific logistics for how to work with them to add
... the extensions to TTML2.



<trackbot> issue-21 -- window anchor points not supported? -- pending review

<trackbot> http://www.w3.org/AudioVideo/TT/tracker/issues/21

glenn: This is about positioning the root container region more flexibly, or other regions relative to it.
... I'm proposing a new tts:position style attribute fairly closely related to the backgroundPosition property
... in CSS 3 image backgrounds and borders. For example you could say "position the bottom edge of the
... region 20% above the bottom edge of the container region".
... So you could say 10% bottom, or center, which would center the region in its container region.
... Take a look at that - I think it will be interesting. I've defined it so that if you have both tts:origin and
... tts:position then in a TTML2 context you'd ignore tts:origin and use tts:position, otherwise you can
... still use tts:origin as a fallback. The presentation in that case may end up different of course.

pal: Do we really need this feature? Positioning has been problematic for a number of implementors in
... the past so I'm concerned about the complexity. What is the use case?

glenn: I'm responding to the issue - someone requested anchor points so I've provided a solution.

pal: This issue was opened in 2008.

glenn: We should bear in mind that there are general uses for TTML2 not just captioning and subtitling.
... There are features that need similar features. We shouldn't confuse implementation complexity with
... syntax complexity. Many browsers implement the CSS feature too, so there are implementations.

mike: How would this work? If you have overflow, extent etc what would happen? Would the anchor remain
... where it was set. That needs to be addressed.

glenn: This only addresses position of the region, not extent or overflow, which are separate.
... In order to compute the position you have to have resolved the extent already. The overflow issue
... is independent of positioning and sizing. So this is only related to position.

mike: I think the combination of the two could result in some interesting effects depending on how it is
... defined.

glenn: There are some extensions coming to the extent attribute, including the ability to say it should be
... computed so that the result is contained in the outer containing block, for example if you're sizing the
... root container region to ensure it fits in the available area of the related media object, and needs to be
... in the center, you'd specify extent="contain" and position="center" and the semantics would work
... alongside another new parameter storageAspectRatio which constrains the related media object's
... shape. Then the root container region is positioned correctly.

mike: I think the original issue (could have been me, I'm not sure!) needs to be mapped from 708 semantics
... into this, whatever we end up doing. I share some of pal's concerns re complexity.

glenn: I agree, and would point out that it's bad design in my opinion to throw out possible features early
... in the process. It's better to propose solutions that can be considered. As the process moves forward
... we can see if they will be implemented and do what is needed, rather than cutting them out too soon.
... This also establishes IPR precedent and commitment by putting them into the FPWD even if they don't
... end up in the final version. This is the wrong time to discuss complexity.

atai: We discussed anchor points in the EBU group some years ago with Sean Hayes. We mostly discussed
... positioning of the region within the root container. We didn't talk about positioning the root container
... in relation to the media object. Just a note. I'm not sure if we have an option for simplification there.

glenn: THere are three applications: 1) positioning the root container region wrt the display or the media object.
... For example a 16:9 display showing a 2:1 media - you may want to position the subtitles in the black
... bar beneath the video.
... 2) Positioning the region within the root container region.
... 3) Positioning background images relative to content or a region. The border rectangle, padding
... rectangle and content rectangle need to be considered.


<trackbot> issue-213 -- Advance notice of deprecation for textOutline -- pending review

<trackbot> http://www.w3.org/AudioVideo/TT/tracker/issues/213

glenn: There's no action - I don't propose that we don't deprecate textOutline. I'll be drafting the
... orthogonal text shadow feature, but they're independent of each other.
... It's already in TTML1 so I propose to keep it.

mike: As long as we end up having the 708 features that can't be emulated with textOutline (drop shadow support).

glenn: The way we defined textOutline is that it extends perpendicular to the tangent of the outline of the
... glyph at any given point, inner or outer. textShadow is an x-y offset vector that translates the outline
... without changing its size.

mike: My concern isn't textOutline but making sure we have text shadow.

courtney: I think that means you won't be able to support all the FCC regulations in TTML.

glenn: I'm proposing not deprecating, so both are available, and I believe it will support all of the options.
... We will need to go through all of the 708 edge styles and verify that they can be achieved.

PROPOSAL: Close this issue.

close issue-213

<trackbot> Closed issue-213.


<trackbot> issue-236 -- Character spacing, i.e. letter-spacing -- pending review

<trackbot> http://www.w3.org/AudioVideo/TT/tracker/issues/236

glenn: this allows introducing tracking in the same way as CSS letter spacing. I've introduced it.


<trackbot> issue-237 -- Inline space -- pending review

<trackbot> http://www.w3.org/AudioVideo/TT/tracker/issues/237

glenn: This is similar - inline space allows the width of an inline box that contains some glyphs,
... for example a span with some content in it within a paragraph. I might want to say 14% of the region
... width, etc. It turns out that in CSS and XSL-FO there are both width and height properties that apply
... to content elements however the semantics are such that for inline non-replaced elements like span,
... width and height are ignored! So, what to do? It turns out there's a nice mechanism in CSS which I'd
... overlooked for a while, called display:inline-block. While you can't say that an inline block is a
... particular width you can say that a block in an inline context is a particular width and height. So I
... introduced those concepts, and said that they magically turn spans into inline blocks to which width
... and height can apply. I've tested it in various browsers and it does exactly what you'd think it does.


<trackbot> issue-285 -- Align rendered rows within a region to each other, and the set to the region -- pending review

<trackbot> http://www.w3.org/AudioVideo/TT/tracker/issues/285

glenn: This is the long standing EBU request for multiRowAlign. We've played around with some options.
... We looked at flexbox, but I recently realised that the inline block mechanism I just described can
... satisfy the same requirement. E.g. A paragraph with a single span in it, the p being the whole width of
... the root container region, and you want to centre the text, but align any broken lines left or right to
... each other within that centre-aligned paragraph. The inline block mechanism allows that too.
... You can specify a separate alignment on the content of the span and that will allow two alignments,
... one to the content of the paragraph and the other to the span. My experiments on browsers show
... this works as desired. If you specify a textAlign on span, which is new, then it results in the promotion of
... the span to an inline block for display purposes. That would allow for example left justified lines in a
... center aligned paragraph.
... This separates out the concepts so the existing semantics don't have to change.

atai: This is an interesting approach that the EBU group should review. I'm not sure it matches the intended
... presentation - does it align multiple lines of text with the longest line in the group? For example
... a centred first (and longest) line, with the second line right aligned to it? Would this work?

glenn: I'm not sure. I need a written down sample or example to check. My proposal does work when
... the line breaks are defined with br elements. If two lines are wrapped in a span with textAlign="right"
... and contained in a paragraph with textAlign="center" then it would first layout the block right aligned
... and then centre the whole block as the paragraph. So this would have the result you want.

atai: ok

glenn: I'd be interested in scenarios where this might not work, according to my reading of the EBU spec.


<trackbot> issue-286 -- Extend the background area behind rendered text to improve readability -- pending review

<trackbot> http://www.w3.org/AudioVideo/TT/tracker/issues/286

glenn: I fixed that by allowing padding to be assigned to a span, and saying if done, it must use
... box-decoration-break:clone semantics.


<trackbot> issue-294 -- Style attribute to prevent overflow by shrinking text to fit on a line -- pending review

<trackbot> http://www.w3.org/AudioVideo/TT/tracker/issues/294

glenn: This is one that I believe John Birch specified and I said that the proposal was about content
... fitting, e.g. automatically reducing the font size to fit the content. Nobody in CSS land or elsewhere
... is doing that, so it would be highly complex to implement. However the region can now be shrink-fit
... to the content. I've proposed a new value for tts:extent: "fit-content" that comes out of a CSS3 spec.


<trackbot> issue-307 -- Conformance language and processor profile rather than content profile. -- pending review

<trackbot> http://www.w3.org/AudioVideo/TT/tracker/issues/307

nigel: Since relevant changes have been made I propose to close this with no further action.

close issue-307

<trackbot> Closed issue-307.


nigel: Please note the liaison from ITU-R WP 6B which came in earlier today and went to member-tt.
... They would like a liaison I think, want to know about our work on WebVTT and IMSC 1 and how
... they relate to each other. They also have some detail questions on IMSC 1.

pal: I'm happy to draft a first response on those IMSC 1 questions.

<scribe> ACTION: pal Draft response to ITU-R liaison re IMSC 1 questions. [recorded in http://www.w3.org/2014/12/04-tt-minutes.html#action01]

<trackbot> Created ACTION-358 - Draft response to itu-r liaison re imsc 1 questions. [on Pierre-Anthony Lemieux - due 2014-12-11].

glenn: I notice the liaison also mentions the ARIB-TT development.

nigel: Yes, I encourage everyone to have a look at the liaison document.
... For next week we have 1 hour set aside and a lot of issues to close on TTML2, hopefully, so in the
... interests of time please could everyone discuss them offline on the reflector as much as possible, so
... we only have to discuss the minimum number of questions?

[adjourns meeting]

Summary of Action Items

[NEW] ACTION: pal Draft response to ITU-R liaison re IMSC 1 questions. [recorded in http://www.w3.org/2014/12/04-tt-minutes.html#action01]
[End of minutes]

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$Date: 2014-12-04 16:06:51 $