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{minutes} TTWG Meeting 2017-05-18

From: Nigel Megitt <nigel.megitt@bbc.co.uk>
Date: Thu, 18 May 2017 16:44:47 +0000
To: Timed Text Working Group <public-tt@w3.org>
Message-ID: <D5438CE7.3FB5A%nigel.megitt@bbc.co.uk>
Thanks for attending today's TTWG meeting. Minutes can be found in HTML format at https://www.w3.org/2017/05/18-tt-minutes.html

We made one resolution:

RESOLUTION: After applying fixes to the outstanding issues, publish the PQ HDR in PNG document as a WG Note.
The review period for this resolution as per the Group's Decision Policy expires on Thursday 1st June. If you have any objection to this resolution please raise it within that period.

In text format:


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

                Timed Text Working Group Teleconference

18 May 2017

   See also: [2]IRC log

      [2] http://www.w3.org/2017/05/18-tt-irc


          Pierre, Dae, Glenn, Nigel

          Andreas, Mike, Thierry




     * [3]Topics
         1. [4]This meeting
         2. [5]IMSC
         3. [6]TTML issue assignment and progress tracking
         4. [7]TTML1 & TTML2 issues, action, PRs, editorial
            actions etc
         5. [8]HDR in PNG
     * [9]Summary of Action Items
     * [10]Summary of Resolutions

   <scribe> scribe: nigel

This meeting

   Nigel: For today, we have 2 hours. I don't think there's
   anything to discuss re TPAC, so
   ... I think we'll be focusing on TTML1 progress, issues, pull
   requests etc. Do we need time
   ... on IMSC?

   Pierre: Yes, should be very quick but there's a blocker there.

   Nigel: I think the HDR in PNG note has had its time, and I
   haven't had any responses, so
   ... let's discuss publishing that as a Note.
   ... Any other business or particular points to raise?

   Pierre: Dae didn't you propose resolutions on a bunch of

   Dae: Yes but they're waiting for feedback from Richard Ishida.

   Nigel: I don't have any other business, but just noting today
   is Global Accessibility Awareness Day.


   Pierre: There's a pull request:

   [11]Added explicit spaces in tts:aspectRatio and tts:activeArea
   definitions (issue #221)

     [11] https://github.com/w3c/imsc/pull/230

   [12]Attribute syntax definition: missing spaces

     [12] https://github.com/w3c/imsc/issues/221

   Pierre: In TTML1 there's prose that has not been imported into
   IMSC1 about spaces being
   ... required between non-terminal tokens. It was never in IMSC1
   even though it followed
   ... the conventions. So here I propose a pull request that
   explicitly adds a single space
   ... between the tokens in ittp:activeArea and ittp:activeArea.
   However Glenn is not happy
   ... with that.

   Glenn: I think many readers would assume that the TTML1 rules
   already apply even though
   ... it is not explicitly stated. By introducing a space there
   we are going against how
   ... attribute syntax is specified in TTML1 and TTML2 since it
   does not do that except to
   ... call it out when those rules do not apply. Also the way it
   is quoted as a double quoted
   ... white space is ambiguous because we cannot tell which
   character it is. Also it does not
   ... work in all contexts even with XML since it is possible to
   escape white space and it may
   ... not be normalised. So the way the comment has been resolved
   is inconsistent and it is
   ... much easier if you simply refer to the TTML1 rule in the
   convention section or something
   ... like that.

   Pierre: Nigel, what's your take on that?

   Nigel: This is new to me, however for the reason that
   implementers should not need to
   ... create a special attribute parser just for these two
   attributes, I would agree with Glenn.

   Pierre: Okay I'll do that. I'll need to copy the text in
   otherwise I would have to reference the
   ... two places in TTML1 where this is defined, one for
   parameter attributes and the other for
   ... style attributes? Oh actually both are parameters. Thanks,
   I'll go ahead.

   Nigel: There are two other pull requests for IMSC - do we need
   to discuss those?

   Pierre: We can do that offline, no need to discuss today.
   ... Also FYI there are two issues Nigel that need your review,
   and everyone in the Group's,
   ... for CR exit criteria.

   Glenn: Question: Pierre, how did you resolve that issue about
   the white space and the
   ... fontFamily expression?

   Pierre: That's still under discussion, there's no pull request
   on that. It's on the IMSC test
   ... suite not on IMSC1.

   Glenn: Your point was based on a presumption about TTML1 that
   may or may not be true.

   [13]FontFamily009.ttml has a spurious space

     [13] https://github.com/w3c/imsc-tests/issues/7

   Pierre: That has an impact on TTML1 and TTML2.

   Glenn: The issue is whether or not space is permitted around
   terms in a comma separated
   ... list, and even more generally whether space is permitted
   around other delimiters, of which
   ... we have a variety. That generic language we were talking
   about for an implied whitespace
   ... between two non-terminals: if you have another kind of
   delimiter there then that language
   ... does not read on the question of if it is permissible to
   have white space between the delimiter
   ... and the term that follows. In this particular issue someone
   had read it as indicating that
   ... white space is not allowed in that context but if you look
   at the original CSS2 grammar
   ... specification from 1998 and this spec you'll find examples
   where white space appears
   ... around terms in a delimiter separated list, and the same in
   XSL-FO. We did not call this
   ... out in TTML but there's a good case for saying that white
   space is permitted.
   ... This will affect all the TTML-based languages.

   Pierre: I've arrived at a different implementation from Glenn

   Nigel: Do we have example data points here? I would expect to
   see "comma space font name"
   ... in real world examples, and I'm sure I've seen that.

   Glenn: I think the original DFXP implementations and TTV does
   permit it.

   Pierre: It would be helpful and relevant to see example content
   here. RGBA values with
   ... white spaces are more complex to process.

   Glenn: I don't think the spec argues this clearly either way.

   Pierre: There are no IMSC tests except for the fontFamily one
   that demonstrate this.

   Glenn: There are some older tests for DFXP that I can go back
   and look at.

   Pierre: At least 2 people in the world read it in a particular
   way, so it would be a
   ... disservice to go back and change TTML1 to make
   implementations incompatible unless
   ... we can show that many documents exist that have that issue.

   Nigel: There's an example at

   that shows comma separated lists.
   ... I just provide this in the spirit of a single data point.
   Look at the second row in the
   ... document requirements section.

     [14] http://bbc.github.io/subtitle-guidelines/#tts-fontFamily

   Pierre: We may extend this to fonts but I'm not comfortable
   extending it across the board.
   ... This is about not making existing implementations stop
   working just by a stroke of the
   ... pen on the spec.

   Nigel: I would go back to my previous point that it should be
   possible to have a single
   ... attribute value tokeniser algorithm rather than being
   required to use different ones.

   Glenn: I don't think we can resolve this but I'd point out that
   the new conventions that just
   ... went into TTML2 explicitly allow for white space around
   commas and semicolons where
   ... they are delimited. That would extend to all argument lists
   that use commas for example.

   Pierre: Unless there's a really compelling reason to do that
   I'm not sure why we'd need to
   ... broaden the scope there and increase the number of test
   cases. Also we would need to
   ... be careful about terminal and non-terminal values, what
   about time expressions?

   Glenn: No, that's explicitly dealt with; white space is
   prohibited from those time expressions.

   Pierre: Not in TTML1. Unless there's a really good reason,
   regardless of CSS, we should
   ... remove flexibility rather than increase it.

   Glenn: For implementers that assume that whitespace is
   permitted, and authors who
   ... assume it is permitted then your position might make their
   assumption invalid.

   Pierre: Only for authors. If we are going to make that change,
   we need to know if authors
   ... have been using that capability.

   Glenn: So we need more input on this.

   Nigel: I agree we cannot resolve it today.
   ... Specifically we would want to know if there are
   implementations that do not work properly
   ... in the case that spaces exist, and if there are documents
   that include additional spaces.

TTML issue assignment and progress tracking

   Nigel: Looking at the milestones, we have 36 open, 47 closed on
   the Editor's list for WR,
   ... which is 56% complete.
   ... And we have 5 open 0 closed on the Group's WR action
   required list.

   Glenn: Approximately 22 have been closed in the last week. If I
   can keep up this rate then
   ... we are going to be pretty close to getting to 100% by the
   end of this month, so that is
   ... my hope.
   ... I noticed that Glenn has offered to work on #20 and has
   offered a pull request,
   ... thank you for that. I'm working on an update to that pull
   request today. Can I assign
   ... that to you Pierre?

   [15]How to specify aspect ratio to understand positioning that
   may apply for display or video

     [15] https://github.com/w3c/ttml2/issues/30

   Glenn: This Pull Request will not be merged instantly.

   Pierre: I don't think 3 days would be adequate for this one.

   Glenn: [assigns issue to Pierre and Glenn] We're both working
   on this right now.

   Nigel: What's next on everyone's slate for issues to pick up?

   Glenn: I'm actively working on a number that I am working on. I
   cleared a number of the
   ... assignments to myself so that others could feel free to
   work on them. Since then I have
   ... picked up a few of them.
   ... In one case I submitted a pull request that was assigned to
   you Nigel.

   Nigel: I noticed that!

   Glenn: Dae, I have a follow-on request on one of the Ruby
   examples that I'd like to ask you
   ... to fine tune so I will coordinate with you on the side on

   [16]Add examples of new features commonly used with Japanese
   content (2 of 2)

     [16] https://github.com/w3c/ttml2/issues/203

   Glenn: Also I'd like to point out that there are number of
   places in the spec where examples
   ... are needed, so Dae if you have a chance and some time we
   would certainly welcome
   ... more submissions on those.

   Dae: I'll give the document another pass-through and see what I
   can pick up.

   Nigel: There's been activity on #128.

   [17]The uniqueness of xml:id needs to be broken for some uses
   of condition

     [17] https://github.com/w3c/ttml2/issues/128

   Glenn: I'll try to add some data points to that today.
   ... I'd appreciate it if you could pick up #224 and #156 Nigel.

   Nigel: Okay I'll look at those and see if I can take them on.

   Glenn: Also #135 clarify timing concepts in relation to SMIL.

   Nigel: We did do some of that already, and there's a note on
   the issue for Pierre to add
   ... something about container diagrams.

   Glenn: At one point there was an ask to more formally define
   the times than in SMIL.

   Nigel: We did the work already in the wiki, perhaps it just
   needs to be validated and formatted
   ... into a pull request.

   Glenn: My worry is it will be difficult to validate.

   Nigel: In that case I would propose a WG Note explaining how we
   interpret SMIL in the context
   ... of TTML.

   Glenn: I think that's a good idea, and could be added to the
   spec later. We need to do it in
   ... a quasi informative manner that can be validated rather
   than making it normative spec
   ... text that may unknowingly break things.
   ... I think all of us have done some implementation work on
   this and came up with different
   ... implementations...

   Nigel: That's a worrying sign.

   Glenn: The amount of test content in relation to timing is
   pretty minimal.

   Nigel: I have a lot of cases that can be generated from the
   EBU-TT Live Interoperability Toolkit's
   ... BDD tests. That can be done for the TTML2 test suite though
   they are subject to some
   ... starting constraints such as parallel only time container
   semantics, and dur only permitted
   ... on body, but they would generate a large number of test
   documents and expected
   ... processing outcomes.

   Glenn: I will also need your help on #96 the extension to add
   date support to time expressions.
   ... I need to read the comments that came in from Nigel and
   Addison. I'm reticent to putting
   ... back in time zone support but I am open to persuasion.

   Nigel: Okay. I will review that and see if I can add a further
   ... Any further points on issues?

   Dae: I will be taking a look, and need to prompt Richard Ishida
   on some of the open issues.
   ... How long should we give the commenter to respond, if we're
   hitting the end of June?
   ... Would 7 days be reasonable?

   Nigel: From the Process perspective we can take a view on each
   issue and we only have
   ... to dispose of all the wide review comments for transition
   to CR, so we could reassess
   ... the state say in the middle of June.

   Pierre: I have a slightly different view - if we take weeks to
   respond to a comment and then
   ... give a short 7 day deadline that might seem funny.

   <inserted> Dae: This is specifically about issues where the
   commenter and I are actively going back and forth and one side
   stops replying

   [18]No mention of isolation for directional controls

     [18] https://github.com/w3c/ttml2/issues/265

   Nigel: This is assigned to you Pierre, and the last comment is
   from Richard.

   Pierre: This is a new feature of CSS with low levels of
   support; unless what we have today
   ... really does not work my view is to defer the feature to

   Glenn: This has already entered the Unicode bidi algorithm.

   Pierre: I'm not the best person to comment on this.

   Glenn: Also Unicode added explicit control characters with the
   isolate semantics, not in
   ... the bidi spec. The original reason for the bidi properties
   in CSS were to provide a stylesheet
   ... mechanism that would express the same information as was in
   the explicit bidi control
   ... characters that would allow authors to avoid using those
   characters. Given the current
   ... state since it is permitted in the character content that's
   a case where you could not
   ... represent it in style information in TTML right now whereas
   in CSS you can. I was going
   ... to suggest that we accept this change and add the necessary

   Pierre: I would not object to that.

   Glenn: I do agree it would be work for implementations and

   Pierre: imsc.js would support it to the extent that browsers
   support it, which is spotty.

   Glenn: The community will demand it so it will come along.

   Pierre: Hopefully we'll have better support when we get to PR.

   Glenn: I'm adding a comment to say that I generally support

   Pierre: I can generate a pull request for it then.

   Glenn: Sounds good to me.

   Nigel: We need to have at least a placeholder for an example
   there too.

TTML1 & TTML2 issues, action, PRs, editorial actions etc

   Pierre: People interested in aspect ratios etc should look at
   the pull request I drafted yesterday:

   [19]Initial pass at rationalizing aspect ratio and pixel

     [19] https://github.com/w3c/ttml2/pull/321

   Glenn: As I mentioned before I am in the process of creating a
   new commit for this branch
   ... which will generate some further discussion.
   ... This will knock off at least 2 or maybe 3 related issues
   which I think I've already
   ... incorporated into #30 by reference at this point.

   Nigel: Regarding mediaOffset Glenn and I had some email

   Glenn: I need to read your message carefully on that so it's
   pending. We are not
   ... synchronised in our understanding at this point. I don't
   have anything specific that I
   ... need input on right now.

   [20]Specify date as well as hours, minutes and seconds in time

     [20] https://github.com/w3c/ttml2/issues/96

   Nigel: In this case I think we need the option of a timezone
   because there are two possible
   ... valid use cases for clockMode="local", one in which just
   whatever local timezone applies
   ... is used, so the timezone is not specified, and the other is
   that a specific timezone is
   ... intended and needs to be specified.

   Pierre: How would you encode the timezone?

   Glenn: Using the same syntax as in the source for this, which
   is SMIL, and the timezone part is based on ISO 8601.

   group: Discussion of the merits and ambiguity/clarity of
   including a timezone component
   ... in local times - Nigel argues in favour on the basis of
   operational utility, understanding
   ... that a local time with a timezone offset is a different way
   to express a UTC time;
   ... Glenn and Pierre argue that if a UTC time is intended then
   a UTC time should be used
   ... and that local times always need to be treated locally.

   Nigel: In that case if we are going to use local in this way we
   need to clarify it.

   Glenn: That seems reasonable.

   Nigel: I've added a comment on the issue.

   [21]Add ttm:mediaTimestamp (or equivalent) attribute

     [21] https://github.com/w3c/ttml2/issues/125

   Glenn: I need to review your input Nigel.
   ... I also need to understand the proposal to use set in #128

   [22]The uniqueness of xml:id needs to be broken for some uses
   of condition

     [22] https://github.com/w3c/ttml2/issues/128

   Pierre: I also need to consider the impact on implementations
   there. The bigger question
   ... of when condition is evaluated was brought up, which is
   somewhat orthogonal but
   ... something we need to consider at some point. It impacts
   more than just this issue.

   Nigel: I agree - this was one of my earliest questions
   regarding the condition mechanism.

   Glenn: My current position is that it needs to be resolved at
   presentation time. Also there
   ... is a special case that can be made that some of the
   semantics of a style element should
   ... not be ignored even though it is conditionally excluded.
   Because of chained referential
   ... styling you might have two or three styles that refer back
   to something that gets incorporated.
   ... If you conditionally exclude a style in the middle of a
   chain does that break the chain
   ... or just exclude those style attributes defined by that
   style element?
   ... This is a case where partial semantics need to be retained.
   I've implemented that in TTXV.

   Nigel: This points to a problem possibly with the use of the
   term "ignore" in that it does
   ... not mean that the element itself is ignored but that the
   things it defines are ignored.

   Glenn: Yes that is exactly the case.

   Nigel: So in terms of action we need to change the term ignore
   or define it better.

   Glenn: I agree that more clarification is needed.

   Pierre: It has to be added to the style resolution process.

   Glenn: I agree.
   ... I have some tests in the TTT test suite that test this.



   <trackbot> action-495 -- Thierry Michel to Update the ttwg
   homepage and publications pages for the new repos -- due
   2017-04-20 -- OPEN


     [23] http://www.w3.org/AudioVideo/TT/tracker/actions/495

   Nigel: I see that this is done.

   close action-495

   <trackbot> Closed action-495.

   PROPOSAL: Publish the PQ HDR in PNG document as a Working Group

   Nigel: I've just spotted that the ICC file claims that it has
   copyright with Adobe Systems.

   Glenn: Apache licensing doesn't allow use of an ICC file; we
   had to make other arrangements.
   ... It was copyright by Adobe.

   Pierre: So Adobe holds a copyright on every ICC file ever made?

   Glenn: No, there's a standard one that's widely used in the
   industry but Apache decided
   ... we could not include that in any Apache project.

   Pierre: This ICC file is bespoke and was made by hand.
   ... Thanks for highlighting this. It was not taken from any
   existing tool.

   Nigel: Presumably we need to update the copyright notice here
   to say W3C.

   Pierre: I will follow up with whoever created it.

   Nigel: I think we can resolve to publish that after making
   those changes.

   Pierre: Okay, if I learn that we cannot change the copyright
   notice on the ICC I will notify
   ... the group.

   RESOLUTION: After applying fixes to the outstanding issues,
   publish the PQ HDR in PNG document as a WG Note.

   Nigel: Thanks everyone. [adjourns meeting]

Summary of Action Items

Summary of Resolutions

    1. [24]After applying fixes to the outstanding issues, publish
       the PQ HDR in PNG document as a WG Note.

   [End of minutes]

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