{Minutes} TTWG Teleconference 2022-12-22

Thanks all for attending this, the final TTWG call of 2022. Minutes can be found in HTML format at https://www.w3.org/2022/12/22-tt-minutes.html


Our next call will be on 2023-01-19.

Until then, wishing you well over the festive season, whatever you’re doing.

Those minutes in text format:

   [1]W3C

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


                Timed Text Working Group Teleconference

22 December 2022

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

      [2] https://www.w3.org/2022/12/08-tt-minutes.html

      [3] https://github.com/w3c/ttwg/issues/235

      [4] https://www.w3.org/2022/12/22-tt-irc


Attendees

   Present
          Atsushi, Cyril, Gary, Nigel, Pierre

   Regrets
          none

   Chair
          Gary, Nigel

   Scribe
          nigel

Contents

    1. [5]This Meeting
    2. [6]Rechartering Formal Objection Council status update
    3. [7]IMSC-HRM
         1. [8]CR1 Exit Criteria
         2. [9]Clarify that the IMSC HRM specifies document
            conformance w3c/imsc-hrm#60
    4. [10]DAPT
         1. [11]ttp:profile on root, and conformance terminology
            w3c/dapt#104
    5. [12]AOB - next meeting
    6. [13]Meeting close

Meeting minutes

  This Meeting

   Nigel: Today we have:
   … * Rechartering Formal Objection Council status update
   … * DAPT
   … * IMSC-HRM
   … * AOB - 1st meeting of next year.
   … Any other AOB?

  Rechartering Formal Objection Council status update

   Nigel: Thanks Atsushi for pointing me at messages that PLH sent
   recently:

   [14]https://lists.w3.org/Archives/Member/

   member-charters-review/2022Dec/0001.html

     [14] https://lists.w3.org/Archives/Member/member-charters-review/2022Dec/0001.html


   [15]https://lists.w3.org/Archives/Member/

   member-charters-review/2022Dec/0000.html

     [15] https://lists.w3.org/Archives/Member/member-charters-review/2022Dec/0000.html


   Nigel: This is partly in response to the Members' meeting at
   1400 on 2022-12-20 and the conversation
   … that I, Philippe, and Florian had about the options for FO
   Council.
   … However, it does mean that the frustration with getting a
   timely response may return if they do not
   … answer quickly. In the meantime, what is going to happen
   about the TTWG Charter that expires
   … at the end of the year?

  Atsushi: As far as I heard, FO Council may not provide
   decision, but provided proposal that TTWG accepted.
   … So if the counter-parties accept that then that would resolve
   the objections, which might be one possible scenario for now.

   Nigel: Yes. My question is what will happen to the TTWG
   Charter?

   Atsushi: In parallel, a short extension is expected, from my
   conversation with Philippe.

   Nigel: Okay, thank you.

   Atsushi: At least with that, possible publications around
   Jan/Feb.

   Nigel: Any more points to raise on this topic?

  IMSC-HRM

    CR1 Exit Criteria

   github: [16]https://github.com/w3c/imsc-hrm/pull/59


     [16] https://github.com/w3c/imsc-hrm/pull/59

   Nigel: Is this still a draft PR?

   Pierre: Yes, to prevent merging, as much as anything else.
   … The outstanding thing is how to label at-risk features.
   … I'm not happy with it.
   … I think we should go back to a simple statement rather than
   linking to issues.
   … It's confusing, and doesn't bring us anything because we
   don't have many features at risk.
   … I propose to remove those links.

   Nigel: I'm not sure what the problem is - I'm actually quite
   happy with it as it stands.

   Pierre: OK, what about you Atsushi?

   Atsushi: I don't have objections

   Pierre: Okay, maybe we should resolve those threads and call it
   done.

   SUMMARY: Proceed as-is

    Clarify that the IMSC HRM specifies document conformance
    w3c/imsc-hrm#60

   <Github> [17]https://github.com/w3c/imsc-hrm/pull/60 : Clarify
   that the IMSC HRM specifies document conformance

     [17] https://github.com/w3c/imsc-hrm/pull/60


   Github: [18]https://github.com/w3c/imsc-hrm/pull/60


     [18] https://github.com/w3c/imsc-hrm/pull/60


   Pierre: Mostly a discussion between me and Nigel.
   … I'm proposing that conformance be expressed in terms of a
   sequence of ISDs
   … generated from a collection of IMSC Documents.
   … My thinking is that there is an unambiguous procedure for
   doing that so
   … I think it's pretty clear. I'm not sure I fully understand
   your concerns Nigel.
   … I understand one practical concern, that the test suite is
   not going to have a sequence of ISDs
   … as artefacts, that I agree with.
   … In my mind the conformance section of the document is very
   different from the testing artefacts
   … and what's in the spec can be more abstract than what is in
   the tests so I don't see the conflict there.
   … I want to understand what you see as the issue with
   conformance being of a sequence of ISDs
   … generated from a group of IMSC Documents.

   Nigel: I completely agree with how you just expressed it but
   that's not what the spec says.
   … It doesn't say that the sequence of ISDs are from an IMSC
   Document.

   Pierre: I think you're concerned with the turn of the sentence
   that starts "Given a sequence of ISDs ..."

   Nigel: Yes I think that's right

   Pierre: Okay, thanks, I'll propose a change to the sentence to
   flip that round.
   … It's important to leave it loose because "given a sequence of
   IMSC documents" the sequence of ISDs
   … is not the same as what you process. First, the last ISD is
   infinite. Second, there's typically some
   … temporal interval used to clip the sequence.
   … I don't think we need to go to that detail in the
   conformance, I think we need to keep it vague.

   Nigel: Two things. Infinite last ISD, and application of
   temporal clipping.
   … Looking at Infinite last ISD, I don't think that makes any
   difference, because there's no work to do
   … on the last ISD.

   Pierre: Unless there's a sequence of IMSC documents and you
   need to move on to the next one
   … before the ISD from the current one ends.

   Nigel: Ah, that's another issue again, about sequence handling
   which I don't think we've formally defined.

   Pierre: That's because the algorithm doesn't care - it just
   cares about ISDs, which is so that we don't have
   … to deal with clipping of ISDs etc.

   Nigel: Let's say there's an error found in an ISD that's
   clipped at the boundary of two IMSC documents.
   … Is it the first doc, the second doc, or the clipping
   metadata?
   … We have no control or knowledge of the clipping metadata, but
   we need to declare what thing is non-conformant.

   Pierre: Is your concern that it will be difficult in testing to
   separate ISD creation from IMSC HRM?
   … Meaning that the results we get might be wrong because the
   ISD creation step was inconsistent across
   … implementations.

   Nigel: My concern is that there are too many unknowns.
   … We have no defined semantic for combining ISDs from different
   IMSC documents,
   … so we cannot point to a source of error if there is one.
   … I think we could reasonably say "here are the rules for ISDs
   generated from one IMSC document,
   … and if you have a way of combining ISD sequences from
   multiple documents, that's fine, you can
   … run the algorithm on that, but we can't tell you what's wrong
   because it's out of our scope".

   Pierre: In my mind it's been straightforward because ISDs have
   a duration and you just stack them.

   Nigel: That's not enough!

   Pierre: Maybe that's where the disagreement is.

   Nigel: You have to have rules for dealing with overlaps.
   … We haven't ever defined that. Something like EBU-TT Live
   does.

   Pierre: In my mind you would never do that because there would
   be an ambiguity.
   … You could say "a non-overlapping sequence of ISDs".

   Nigel: You have to know how the inevitable overlaps are
   generated.

   Pierre: You could say that the overlaps have to have been
   resolved.

   Nigel: But then that resolution depends on some algorithm we
   haven't specified and don't know.
   … We can't assess conformance given an important missing step.

   Pierre: We could require that the test inputs are single IMSC
   documents, synthesised from ISD sequences.

   Nigel: That would be fine.

   Pierre: That would remove the need to deal with overlap.

   Nigel: Yes, we need to move overlap resolution elsewhere.

   Pierre: So in my mind the algorithm is purely about a sequence
   of ISDs, and we don't care where they come from,
   … but in testing we only test single IMSC documents.

   Nigel: I think we should put all the overlap resolution and
   recombination into an IMSC document outside the spec,
   … instead, the input is one IMSC document that generates the
   sequence of ISDs, and that one document
   … is a pass/fail.
   … And we can note that some folk might have schemes where there
   are multiple IMSC documents that
   … generate multiple ISDs, and that's great, but they have to be
   responsible for generating an IMSC document
   … that generates the equivalent sequence of ISDs.

   Pierre: Okay I can take a stab at that, I think I understand,
   thanks.

   SUMMARY: @palemieux to draft an edit as per the above
   discussion.

  DAPT

   Nigel: Cyril, any points to raise to the group?

   Cyril: Mainly same as last time, editing continues.
   … We can talk about the profile issue.
   … Nigel, I'm working on your notion of transcript still!

   Nigel: Yes, there are two pull requests that both deal with
   those in different ways.

   Cyril: Yes, the first pull request didn't define the terms and
   was tricky to understand.

   Nigel: If it would help I can merge the two pull requests so
   you can see the changes all together.

   Cyril: Yes, go ahead.

    ttp:profile on root, and conformance terminology w3c/dapt#104

   github: [19]https://github.com/w3c/dapt/issues/104


     [19] https://github.com/w3c/dapt/issues/104


   <Github> [20]https://github.com/w3c/dapt/issues/104 :
   ttp:profile on root, and conformance terminology

     [20] https://github.com/w3c/dapt/issues/104


   Cyril: I'm happy that we're digging into this but we need to
   make it easy for new folk to understand.

   Nigel: I think #103 is improving this.

   Cyril: From a video world, having two profiles is confusing and
   we need to clarify it.
   … They don't know about processor profile vs content profile.

   Nigel: This issue came from a conversation with Glenn about
   some things I wanted to do that
   … TTML2 didn't seem to allow.
   … The starting point is TTML1 backwards compatibility.
   … For DAPT, we simply aren't interested in that.
   … We only want to use contentProfiles and possibly optionally
   processorProfiles, but not ttp:profile
   … but all the relevant feature designators in TTML2 include the
   TTML1 #profile, and effectively require
   … implementers to code for ttp:profile even though we are
   prohibiting its use.
   … Glenn proposed a way to express this in the formal language
   of TTML2 profiles, which I've done
   … in #103. It essentially defines an extension for this one
   thing and says "this is prohibited".
   … There's a message from Glenn that I haven't read yet about
   TTML2 handling of different values of the
   … value attribute on the ttp:feature element.
   … The essence is we want to be able to say "it's permitted in a
   document, and must be implemented in a processor"
   … which doesn't seem possible in TTML2. I think he's pointing
   me at something I missed.

   Cyril: Every standard has that, optional features that must be
   supported by the player.

   Nigel: Of course!

   Cyril: I'm not clear about this processor profile part.

   Nigel: One of the things I've done is move the profile
   definition into the appendix, still normative,
   … but kept the important/interesting stuff that we need people
   to understand to before the appendices.
   … It keeps the formality but makes the document seem shorter.

   Cyril: I like that idea.

   Nigel: At the moment I've had to define a content profile and a
   processor profile distinctly,
   … and it'd be much better if we could have only one. I will
   keep working with Glenn to understand if
   … I can actually do that.

   SUMMARY: @nigelmegitt to continue talking to @skynavga about
   how to simplify this.

  AOB - next meeting

   Nigel: Next meeting is scheduled for 2023-01-05. I can't make
   that.

   Cyril: I also sent regrets for that.

   Gary: Might be worth cancelling.
   … I think a lot of people are out so there won't be much to
   discuss anyway

   Nigel: Okay I'll cancel and our next call will be on
   2023-01-19.

  Meeting close

   Nigel: Thanks everyone for all your work this year and for
   suffering through the great TTWG Charter fiasco.
   … Have a good break, look forward to seeing you next year.

   Cyril: Thank you for your chairing!

   Gary: Yes, thank you.

   Atsushi: Thank you.

   Pierre: Warmest wishes for the holiday season.

   Nigel: [adjourns meeting]


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Received on Thursday, 22 December 2022 17:31:08 UTC