Meeting minutes
This meeting
Nigel: Thanks all for joining the last TTWG meeting of 2025
… and in case I don't have time later, also thank you for the work you
… have all put in all this year.
… Agenda for today:
… DAPT
… DAPT and IMSC compatibility
… IMSC 1.3
… AOB about group membership news
… and that's it for today.
… Any other business or points to make sure we cover?
no other business
DAPT
CRS Publication
Nigel: We published a new CRS today!
… DAPT CRS 18 December 2025
… "This Candidate Recommendation is not expected to advance to Recommendation any earlier than 15 January 2026."
… Thank you all for working on that.
DAPT issues labelled for the agenda
Nigel: I just closed w3c/dapt#307 with a comment that the CRS has been published.
MAY contain zero or one ... objects should be MUST w3c/dapt#324
github: w3c/
Nigel: We discussed this last time, 2 views expressed.
… I don't mind either way, but would be good to get Cyril's view.
Cyril: It says MAY contain zero or one?
… It's weird to put a normative requirement with a MAY.
… You could have 2, right?
Nigel: It's sort of unclear, yes.
Andreas: As written, if something is not permitted explicitly then my understand is it is not allowed.
… So you cannot have 2 things. Otherwise you'd be allowed to put anything in because we never say
… that ...
Cyril: You're saying it's automatic that 1 is the limit because it's constrained elsewhere?
… And the sentence could be removed without harming the spec?
Andreas: No you need to say you are allowed to put one object in, but you cannot put more than 1 in,
… and also you cannot put another one in. The text with MAY is saying you can.
Cyril: Either MAY put 1 so 0 is an optional possibility, or use MUST with 0 and 1.
… But using MAY with 0 or 1 is unusual I guess.
Andreas: For me I haven't found some similar requirement with an optional field where 0 or 1 is required.
… For me it is just a typical multiplicity of 0..1 and would be fine.
Cyril: Happy to leave the text as is, the normative part is you can put 0 or 1.
Nigel: Yes.
… If we did change it to MUST I would class that as an editorial change.
… Close with no change?
Cyril: Good with me
Andreas: OK
SUMMARY: Close with no change
DAPT and IMSC compatibility (editorial)
Add section about IMSC compatibility w3c/dapt#333
github: w3c/
Pierre: Nigel and I discussed this in a chat.
… Because IMSC prohibits use of features that are not supported,
… it wouldn't support DAPT features like audio.
… But that doesn't mean that it is impossible to build a player that would play both.
Cyril: The subset of DAPT documents that do not contain any audio could be IMSC compatible, right?
Nigel: Yes that's right
… My thinking is that this is not a problem.
… The analogy I draw is with images and text - we don't provide a mechanism in IMSC Text to
… include images. They're another representation of the text, potentially.
… And so is audio.
Nigel: In the pull request (and for IMSC too) I included a section on signaling,
… and an informative appendix on compatibility with other TTML based specifications
… and within that, one example, which is IMSC Text.
… [summarises the changes in the pull request]
… The equivalent IMSC pull request is w3c/imsc#625, again, editorial.
… Any thoughts about this.
Cyril: You're looking for review?
Nigel: Yes, the IMSC pull request was opened 2 weeks ago, the DAPT one a few days later.
… I need reviews before I can merge.
… These are editorial changes.
SUMMARY: Group to review
Add DAPT conformance signaling w3c/imsc#625
github: w3c/
Discussed in the context of w3c/dapt#333
SUMMARY: Group to review
IMSC 1.3
CRS publication
Nigel: We published the CRS today
IMSC 1.3 CRS Snapshot 18 December 2025
Nigel: Thank you again all for your work on this.
… "This Candidate Recommendation is not expected to advance to Recommendation any earlier than 15 January 2026. "
Atsushi: Sorry for the delay in this publication
Atsushi: I need to update the formulation for streamlined publication so I will try to submit
… a PR for that tomorrow.
… The configuration needs to match the current status.
Pierre: In the spec or in the repo?
Atsushi: In the repo
Pierre: Thanks, I won't touch that.
Atsushi: I also need to check the configuration in the spec itself so I will do that.
Pierre: I was just about to modify the spec so you'll do that?
Atsushi: Just the metadata.
Pierre: So you'll change the spec to match the published CR?
Atsushi: Yes
Pierre: OK thanks I won't touch it then.
Atsushi: I also need to work on metadata [scribe missed] so let me work on that shortly.
Pierre: OK
Issues and pull requests for discussion
Nigel: No issues or pull requests are labelled as Agenda, that we haven't already discussed.
Pierre: There are a couple of issues I will open pull requests for.
Pierre: We should step through them and check the status, if we still want to do them, then I'll work on them.
Nigel: I see 7
Pierre: Compatibility with DAPT, you assigned yourself Nigel. Still want to work on it?
Nigel: There's a pull request open.
Pierre: ARIB liaison. It's a long standing issue. Do we know when we will hear back from ARIB on this,
… recall IVS?
Nigel: In our joint call with APA and MEIG Ohnata-san said he would send something but I haven't received
… anything yet as far as I know.
… Atsushi, have you?
Atsushi: I had some chat with him yesterday offline during Japanese member meeting,
… but for ISO10646 character class there is some need for clarification within the ISO side,
… so there was a call for a comment within Japanese ISO colleagues, so they may reply to our clarification
… questions shortly, for which ids should be included in the Japanese character class.
Pierre: The timing is important - do we have an estimate of "shortly"?
Atsushi: It should be this month.
Pierre: OK, then my recommendation is to schedule this for the Rec publication, and if we have not
… received anything within the next month we should move on.
Nigel: What does "move on" mean?
Atsushi: It's something to fix in ISO.
Pierre: I'm talking about the definition of IVS
Atsushi: That will be answered shortly.
Pierre: My definition of "move on" is remove it if we are not certain we are doing the right thing,
… and we can add the Japanese character set later on when we're more certain.
Nigel: That would be a big shame, but I understand your logic.
Pierre: I know, I hate it, and I don't know how to make it go faster.
… We could also just have a pointer to ARIB directly, since it is publicly available.
… It is not ideal, but at least helps the reader find some information, as a fallback.
… Ideally we will receive clear feedback within the next month and this will not be an issue.
… Does that make sense to you Nigel, and Gary?
Nigel: It does to me. I also don't like it but can't think of a better way.
Gary: Yeah I don't know of anything better.
Pierre: A month seems reasonable.
Nigel: Yes
Pierre: Next is 612, which I'll fix.
… Next, 605, I don't know what the implications are on the tooling.
Nigel: I would say it's not massively important, it's nice to have
Pierre: On June 22 Atsushi pointed out there's some implication because the name of the file
… is used in the URL of the ED so there would need to be a redirect so that old documents point to the new
… location, so some infrastructure work.
Nigel: I'm asking myself if it is worth the trouble.
Pierre: My answer is No!
… I think we should just remove it from 1.3 and not agonise on it.
… [removes it]
… Next is 604, order subsections alphabetically
… There's a long clause called Additional Provision, and the sections are ordered historically.
Nigel: Will it break links? I don't think so.
Pierre: I think you're correct. Maybe not all of them even have links.
… That could be an opportunity to make sure they all do.
… I'm game, it's ugly as it is.
Nigel: So proceed with that one?
Pierre: I will do that.
Nigel: thank you
Pierre: Next is 553, in the introduction. Nigel had taken that on.
Nigel: I would still like to do that, but I won't get to it until January, so it will be quite tight.
Pierre: Again this is optional, if you haven't had time we can decide not to do it.
… The next one is 524, semantic layers. That one I think we had decided ...
Nigel: For that one, I think if we merge the DAPT compatibility pull request we can point to the
… availability of DAPT metadata as a way to convey additional semantic information through the
… authoring process, and potentially also use that in a suitable player during presentation.
… However there would be no normative requirement on players to do so.
Pierre: The original comment was to specify required behaviour
Nigel: Not sure I read it that way
Pierre: That means the player has an expected behaviour to make a decision based on metadata
Nigel: I feel like a player that uses DAPT metadata to make additional presentation decisions is
… still available as a progressive enhancement.
Pierre: Then it's outside the scope of IMSC, I don't know how you'd write that in the spec.
Nigel: Two things.
… First, there's some informative text in the pull request that can partially answer this.
… Second, I think we could point to that change, assuming we make it, in this issue #524, and suggest
… to APA WG that it fulfils their request.
… My message would be that we have provided the tools and now it's up to the market to decide
… to adopt it before we standardise it.
Pierre: So we have come up with tools and if there's a desire to use them we'll do it in a future version.
Nigel: That was all of them
Pierre: But there's one missing about the superscript accessibility to match the a11y tracker issue.
… It's more general than superscript and subscript accessibility, it's that when you are rendering
… an IMSC document you want to make it accessible, and for mapping fontVariant specifically there are
… some accessibility concerns.
… I'll create a new issue.
… I'll propose a pull request to match.
Nigel: Fantastic, thank you
AOB - group membership news
Nigel: My understanding is Movielabs plans to leave W3C so Pierre will be ejected from the TTWG!
… I hope we can invite him back as an IE to help shepherd through publication of IMSC 1.3 as a Rec,
… and maybe longer too.
Nigel: We're officially out of time but if you are able to stay on, I prepared a brief section looking back
… at Pierre's time at W3C (so far!).
… The first email I could find from Pierre was from 2012, sending Regrets!
Nigel: Searching, since then Pierre has sent 778 emails to W3C mailing lists, an average of about 5 per month, and not all of them were Regrets!
… Though mysteriously, on 1 Nov 2012 Pierre noted that he wasn’t present at the 2012-11-01 TTWG meeting
… because he was at TPAC! Suggests that TTWG didn't have a meeting at TPAC that year.
… What was the context at the time?
… In December 2012 Pierre set up the Timed Text Task Force under the Web and TV (interest?) group, which,
… according to the wiki page, was initially focused on:
… "Develop recommendations to facilitate the use of TTML and WebVTT content on the Web, including interoperability with other timed text formats."
Timed Text Task Force wiki page
Nigel: Not meaning to throw shade at Pierre, this problem still exists, and it's really hard to resolve.
… Then we had the member submission of CFF-TT published 7th June 2013,
… First public working draft of IMSC 1st May 2014
Nigel: First Rec of IMSC 1 was published on 21 April 2016
… Since then 4 more versions of IMSC, 3 at Rec, and 1.3 on the way.
… And Pierre also helped as Editor of TTML1, first listed as Editor on TTML1 3rd Ed CR on 24 April 2018
… Really there’s too much history and hard work here to go into in any detail at all, but I want to thank Pierre for all of it,
… I’ve certainly appreciated all his input during the time I’ve been working in this area. It’s not always been straightforward!
Pierre: Thanks Nigel.
… I want to thank Movielabs for the support all these years.
… The work on IMSC and TTML, and also MSE and EME would not be what they are today without the support of Movielabs.
… In general it’s been a great experience.
… We want to be careful, I might be back in a month!
… It’s a great moment to note the support and effort that Movielabs has put in over the years in TTWG and elsewhere in W3C.
… I’m not disappearing, the goal is to get IMSC 1.3 to Rec.
… I plan to help with that, and you know where to reach me.
… I will remain a member of the mailing list anyway.
Andreas: Just to add I fully support what Nigel said and you should take every opportunity to thank you for this important work.
… It’s really incredible what you and Movielabs have done. Hope you are able to rejoin as an IE.
Pierre: Thank you Andreas. Anyway we talk every month or week!
Meeting close
Pierre: Wishing you all a good holiday.
Nigel: Yes, that's what comes at the end of this meeting!
… Have a good break everyone who gets one, thank you again for all your
… work in 2025, let's do more in 2026.
… [adjourns meeting]
Next meeting is 15th January