{Minutes} TTWG Meeting 2021-01-07

Thanks all for attending today's TTWG call. Minutes can be found in HTML format at https://www.w3.org/2021/01/07-tt-minutes.html

In text format:

   [1]W3C

      [1] https://www.w3.org/

                Timed Text Working Group Teleconference

07 January 2021

   [2]Previous meeting. [3]Agenda. [4]IRC log.

      [2] https://www.w3.org/2020/12/17-tt-minutes.html
      [3] https://github.com/w3c/ttwg/issues/171
      [4] https://www.w3.org/2021/01/07-tt-irc

Attendees

   Present
          Andreas, Atsushi, Gary, Nigel, Pierre

   Regrets
          Cyril

   Chair
          Gary, Nigel

   Scribe
          nigel

Contents

    1. [5]This meeting
    2. [6]2021 Workplan
    3. [7]Meeting close

Meeting minutes

  This meeting

   Nigel: Today I only put one item on the agenda! Which is what
   we aim to do this year
   … Any other business?

   group: [no other business]

  2021 Workplan

   Nigel: End of last year, I asked what members want to achieve.
   … Our group has fewer participants than before so I think it
   makes sense to try to focus
   … on a small number of achievable goals (e.g. 1), do those and
   then move on to the next thing.
   … Happy to have an open conversation about this.
   … For me, coming off the back of the last meeting, I think
   there are several useful achievable things,
   … and prioritising them is important.
   … For example:
   … * User customisation semantics for captions and subtitles
   … * Just getting TTML2 to Rec?
   … * ADPT to CR
   … Those are just three from me. Can I open the floor - any
   comments or suggestions, or desires?

   Gary: For me, it would be to move WebVTT forward.

   Nigel: What do you mean by that?

   Gary: There are a bunch of pull requests that need to be
   addressed.
   … Basically get WebVTT into a place where we can move it
   towards PR,
   … particularly with the live standard addition, with all the
   features pared down to what
   … is deployed, so then we can start adding the features that
   should be in but
   … are not yet available, after the fact.

   Nigel: So marking some features as "candidate" status?

   Gary: Yes

   Nigel: On the user customisation front, I've implemented a
   prototype of all the options in CTA-CEB35 on top of imsc.js
   … and it made me wonder if we need to define semantics for user
   customisation that can work interoperably across players.

   Gary: For TTML and WebVTT?

   Nigel: Yes

   Gary: Having a single place that defines what possible user
   customisations should be would be great
   … and we may want it to go into detail about how it applies to
   TTML and WebVTT as well.
   … Alternatively we could just list out the customisation
   options and then WebVTT and TTML can reference that and
   … say how they apply to themselves.

   Andreas: Regarding the first, to gather information about how
   subtitle customisation should look, are you thinking of a
   general document
   … that would be applicable to any captioning format?

   Gary: Yes I don't see why not
   … If it makes sense. We could always say "if it only makes
   sense to format X" for some reason, then mark it as such.
   … For most of the standard stuff we're used to it doesn't
   matter what caption format it is coming from.

   Nigel: One question is whether the customisation should be only
   at the presentation side or should be
   … constrained to style attributes and properties that are
   already available in the format.

   Andreas: This could be an interesting part, how to deal with
   customisation requests that aren't supported in the incoming
   format.
   … And how to deal with customisation requests that would
   contradict the author's intention.
   … Those are all cases that we meet in operation. If we see for
   example the existing options available in
   … our OSes or TVs they may possibly not really look at the
   author's intention or what the incoming format is capable of.

   Nigel: My go-to example for that is text colours, where a one
   colour outcome is too simple, and users in the UK anyway need
   to see different
   … colours, and authors set colour as an intent. So I
   implemented a colour map customisation to set a palette.

   Andreas: And there's a need for the user to say whether they
   want to override what's set, or only set if something is
   missing.

   Gary: That's what the Apple model is.

   Nigel: I find it hard to understand given that in TTML anyway
   almost all the style attributes have a default value, so how
   would
   … the system know if the author's intent was captured by
   deliberate omission or by specifying something?

   Andreas: We should start with concrete examples and match
   against common practices in different countries, and also try
   it out against
   … existing customisation interfaces.
   … From there we could get a feeling what direction we could
   head with our documents and try to work out some
   … first recommendations.

   Nigel: What I had hoped might be a small achievable goal seems
   to have escalated very quickly into a very big complicated
   … goal that isn't easily achievable, which is probably
   reasonable!

   Gary: You'd start off with a set of knowns, like FCC, CVAA etc
   and consolidate into one document, and work out what that
   means,
   … rather than doing everything at once.
   … Then get deeper after that.

   Nigel: Yes, I think that's right.

   Gary: Otherwise we'll never get anything done.

   Nigel: CTA already did a lot of this, but at a lightweight
   level from a technical perspective, and there are also the
   MAURs.
   … The question is whether this group should do anything beyond
   that.

   Andreas: We should look at non-US sources too, like in Europe.
   In Germany all HbbTV subtitles are customisable but it's not
   mandated or written down.

   Nigel: Something is written down though?

   Andreas: Yes, for example HbbTV subtitles are based on user
   tests made in different EU funded projects.
   … So there are sources for that.

   Gary: Definitely this shouldn't just be a US-UK subtitle user
   customisation options.

   Nigel: +1

   Pierre: The first step might be to collect all this information
   in one place, if it is already done.

   Nigel: That could be published as a WG Note very easily.

   Pierre: From an implementation perspective the pitfall to avoid
   is doing something from one territory, and then
   … someone says "what about here" and then the API gets more and
   more complicated.
   … To deal with all the different models.
   … If we could rationalise all the existing practices that would
   be ideal.
   … Maybe start with a subset of all those practices. But in my
   mind the goal is to avoid
   … 3 or 4 APIs, one for each style of customisation, if it can
   be avoided.

   Nigel: I also wondered if there are any topics where we should
   have a "virtual f2f" meeting, maybe a couple of 3 hour calls in
   a week.

   Pierre: If we can frame the customisation question in a good
   way then it could make sense to share that more widely
   … and invite a wider group of interested people in to discuss
   in a "workshop" (but don't call it that).

   Nigel: Agree

   Nigel: The in-flight Rec activities that are not at "stage 1"
   are TTML2 CR and WebVTT CR
   … Speeding up TTML2 would need us to go and do a load of
   implementation work, possibly.
   … Gary has already explained the idea for WebVTT which sounds
   achievable.
   … Are there any other candidates for things to work on?

   Gary: There's working with CSS WG around viewport units in the
   video element.

   Nigel: Yes, thank you for the reminder.
   … The other CSS related thing is trying to advance e.g.
   fillLineGap, where it's in need of tests and implementation.
   … I'm not comfortable saying that's the activity of this group,
   but it could be that the members of this group are
   … motivated to push it on, and if that takes up their time it
   could be a bit distracting, albeit useful.
   … From my own point of view, I'm struggling to prioritise
   subtitle customisation vs the AD profile of TTML2;
   … in the BBC anyway it may be easier to get momentum from
   others on subtitle customisation, which may steer me.

   Nigel: What do you think of the general idea of trying to
   narrow down our activities to a small number of deliverables
   and focus on them?
   … Does it seem like a sensible approach?

   Pierre: Can you summarise what's left in TTML2 to get to
   publication?

   Nigel: It's completing the CR Exit Criteria for the
   Implementation Report.

   Pierre: What's missing? Is it easy or hard?
   … It'd be nice to finish that spec. These other things are
   interesting but they could be a lot of work.

   Nigel: The CR Exit Criteria say no feature is added/removed so
   none is at risk, but 2 independent implementations are needed
   for each
   … modified feature.
   … The Implementation Report shows 1 passing implementation for
   all the validation tests, but only 1 for one of the
   presentation tests.
   … If we had 2 implementations for every test it would be
   totally straightforward, but we're a long way from that.

   Pierre: Is it possible to switch to the candidate feature mode?
   It's not good to have this hanging.

   Nigel: I'm not sure we're allowed actually, to introduce that
   to an existing Rec.

   Pierre: We could go back to WD and round the loop?

   Nigel: Yes but we'd have to call it something other than TTML2,
   I suspect.

   Pierre: We don't have to have two passes for every test?

   Nigel: No, if we could refactor from features to tests we could
   possibly show that 1 validation test and 1 presentation test
   count as 2 passes.
   … But right now that could only possibly affect one feature.

   Pierre: I'll look at the presentation tests, it may be that we
   have some options.

   Nigel: It seems to me from this conversation that we have quite
   strong motivation to push WebVTT and TTML2 on, and
   … also good energy behind starting small with customisation in
   a way that can be extended later.
   … And user customisation could be a good topic for an extended
   meeting of some form (extended in time and attendees).

  Meeting close

   Nigel: Thanks, this has been useful. Our next call is in 2
   weeks. In that time I may be able to look at the TTML2 IR and
   pull it apart to
   … work out what we really need to achieve to meet the exit
   criteria.
   … Thanks everyone, happy new year again, see you in 2 weeks.
   [adjourns meeting]

   group: [general wishes of happy new year]


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