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Re: Minutes from today's TTWG meeting

From: David Ronca <dronca@netflix.com>
Date: Mon, 19 Sep 2016 13:50:51 -0700
Message-ID: <CAMjV-FjK9daJCvtn5ZjNphv+Zjd4orPjPr6wRcghKnXO-1_KDA@mail.gmail.com>
To: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Cc: Nigel Megitt <nigel.megitt@bbc.co.uk>, Public TTWG List <public-tt@w3.org>
CR requires 2 implementations of every feature in the specification,
correct?

D

On Mon, Sep 19, 2016 at 1:30 PM, Silvia Pfeiffer <silviapfeiffer1@gmail.com>
wrote:

> There's nothing stopping the group to decide to move WebVTT to CR right
> now. Why not just get it done?
>
> Best Regards,
> Silvia.
>
> On 20 Sep 2016 3:33 AM, "Nigel Megitt" <nigel.megitt@bbc.co.uk> wrote:
>
>> Thanks all for a very productive first day of our Lisbon TPAC face to
>> face meeting. Minutes can be found in html format at
>> https://www.w3.org/2016/09/19-tt-minutes.html
>>
>> We made 1 resolution:
>>
>> *RESOLUTION: If we do not move WebVTT to CR in this Charter period then
>> we will not include it in any new Charter.*
>>
>> The review period for this resolution under our Decision Process ends on
>> Monday 3rd October.
>>
>> Minutes in text format:
>>
>>    [1]W3C
>>
>>       [1] http://www.w3.org/
>>
>>                 Timed Text Working Group Teleconference
>>
>> 19 Sep 2016
>>
>>    See also: [2]IRC log
>>
>>       [2] http://www.w3.org/2016/09/19-tt-irc
>>
>> Attendees
>>
>>    Present
>>           Rohit, Nigel, Glenn, Thierry, Dae, Andreas, David,
>>           Pierre
>>
>>    Regrets
>>    Chair
>>           Nigel
>>
>>    Scribe
>>           nigel
>>
>> Contents
>>
>>      * [3]Topics
>>          1. [4]Agenda bash
>>          2. [5]Plan for Joint Meeting with Web & TV IG
>>          3. [6]WebVTT stuff
>>          4. [7]Tagging
>>          5. [8]TTML1 Errata
>>          6. [9]TTML2 Pull Requests
>>          7. [10]IMSC 2
>>          8. [11]Agenda bash
>>          9. [12]TTML2 implementation work
>>      * [13]Summary of Action Items
>>      * [14]Summary of Resolutions
>>      __________________________________________________________
>>
>>    <scribe> scribe: nigel
>>
>> Agenda bash
>>
>>    group: [discusses topics on meeting page
>>    [15]https://www.w3.org/wiki/TimedText/tpac2016#Schedule
>>
>>      [15] https://www.w3.org/wiki/TimedText/tpac2016#Schedule
>>
>>    <glenn> +Present Glenn
>>
>>    nigel: Seems like the topics list is pretty close to the order
>>    we want to cover stuff in.
>>
>> Plan for Joint Meeting with Web & TV IG
>>
>>    nigel: We are meeting the Web & TV IG at 11, so need to provide
>>    an update etc.
>>    ... Discusses proposal for Web & TV IG consisting of update on
>>    our work in TTML,
>>    ... audio description requirements, issue of relationship
>>    between encoded video, media player
>>    ... and timed text presentation; live contribution and BBC
>>    subtitle guidelines. (last two points from Nigel with a
>>    different hat on!)
>>
>>    andreas: I have some slides to discuss on TextTrackCue
>>    interface support for different formats in HTML5.
>>    ... I would also point to the unconference session on this on
>>    Wednesday. They may also
>>    ... want to log this as work that needs doing by a Web & TV IG
>>    task force.
>>
>>    nigel: Good idea, let's do that ahead of my stuff on AD, live
>>    contribution etc.
>>
>>    andreas: [Previews slides] including missing MIME type on track
>>    element in HTML5
>>
>>    nigel: Thanks, let's do that after the TTWG update and if
>>    there's time to hand back to me for the other parts then let's
>>    do that.
>>
>> WebVTT stuff
>>
>>    david: Number one priority is to find a new Chair to cover this
>>    topic - I've indicated already to
>>    ... plh etc that I don't have the time to devote to this.
>>
>>    glenn: What's the status of implementation work?
>>
>>    david: At Apple it's bug fixing, keeping up with customers.
>>
>>    glenn: On the Chrome and webkit list I don't see much activity.
>>    I am not following mozilla or Edge.
>>    ... What's the status in other groups e.g. MPEG referencing
>>    WebVTT?
>>
>>    david: The Chair does need to make progress on moving it to Rec
>>    so it can be normatively referenced.
>>    ... There is implementation work excluding region support in
>>    many implementations.
>>
>>    andreas: I think there have been updates to the specification
>>    that have not been reflected in
>>    ... implementations so this is a problem.
>>
>>    nigel: I've noticed that too - Simon made some really good
>>    changes around 10-11 months ago,
>>    ... which i suspect have not been implemented. I'm not sure
>>    about the status of editing to
>>    ... address the readability review feedback.
>>
>>    david: Apple's implementations predate those changes.
>>
>>    andreas: It's hard to know if those changes will ever make it
>>    into implementations.
>>
>>    nigel: From a BBC perspective there are features that are
>>    essential for accessibility that look
>>    ... like they would have to be put at risk for CR due to lack
>>    of implementation, so that would
>>    ... be a "red flag" for me.
>>    ... For example the BBC's editorial guidelines at
>>    [16]http://bbc.github.io/subtitle-guidelines/
>>    ... cannot I believe be met by most implementations of WebVTT
>>    right now.
>>
>>      [16] http://bbc.github.io/subtitle-guidelines/
>>
>>    action-475?
>>
>>    <trackbot> action-475 -- Nigel Megitt to Contact the chair of
>>    the web & tv ig to ask about schedule and joint meeting time.
>>    -- due 2016-07-28 -- OPEN
>>
>>    <trackbot>
>>    [17]http://www.w3.org/AudioVideo/TT/tracker/actions/475
>>
>>      [17] http://www.w3.org/AudioVideo/TT/tracker/actions/475
>>
>>    nigel: oops I meant:
>>
>>    action-473?
>>
>>    <trackbot> action-473 -- Thierry Michel to Contact co-chairs
>>    and essential parties on how to move forward on vtt; need an
>>    action plan -- due 2016-06-30 -- OPEN
>>
>>    <trackbot>
>>    [18]http://www.w3.org/AudioVideo/TT/tracker/actions/473
>>
>>      [18] http://www.w3.org/AudioVideo/TT/tracker/actions/473
>>
>>    nigel: Thierry did this, but I don't believe we have an action
>>    plan.
>>
>>    david: We need a suitable volunteer to go through the review
>>    comments and respond.
>>
>>    thierry: The Community Group has looked into the review
>>    feedback - about 30 comments
>>    ... have been discussed: that's the current status. Now those
>>    comments need to be approved
>>    ... by the TTWG (and discussed) and then we should send those
>>    responses to the commenters.
>>    ... At some point we need to coordinate between the CG and the
>>    WG to progress those.
>>    ... This has not changed for more than a year, probably because
>>    some people involved have
>>    ... left and Simon does not participate actively in the WG. We
>>    are experiencing joint work with
>>    ... a CG and a WG and we need to invent a process to deal with
>>    this.
>>
>>    nigel: This works both ways - the WG also has not scheduled any
>>    effort to work on this.
>>
>>    andreas: I'm not really convinced that the CG exists as a
>>    traditionally defined group.
>>
>>    nigel: Shall we close the action? The "contact the chairs" part
>>    is done, we're missing an action plan.
>>
>>    david: Leave it open.
>>
>>    action-473: Discussed in TTWG F2F 2016-09-19 - need a volunteer
>>    to progress this, possibly a new Chair.
>>
>>    <trackbot> Notes added to action-473 Contact co-chairs and
>>    essential parties on how to move forward on vtt; need an action
>>    plan.
>>
>>    action-396?
>>
>>    <trackbot> action-396 -- David Singer to Produce evidence of
>>    request for wide review for webvtt, for the archive -- due
>>    2015-04-17 -- OPEN
>>
>>    <trackbot>
>>    [19]http://www.w3.org/AudioVideo/TT/tracker/actions/396
>>
>>      [19] http://www.w3.org/AudioVideo/TT/tracker/actions/396
>>
>>    david: I have not yet done this.
>>
>>    action-396: TTWG F2F meeting 2016-09-19: David has not been
>>    able to do this yet.
>>
>>    <trackbot> Notes added to action-396 Produce evidence of
>>    request for wide review for webvtt, for the archive.
>>
>>    nigel: TO be controversial/challenging, WebVTT has been on our
>>    Charter since 2013 and we
>>    ... have made very little progress. Should we drop it?
>>
>>    david: If we don't complete it in this Charter period [end
>>    March 2018] then we should not
>>    ... recharter it - I propose that as a resolution.
>>
>>    PROPOSAL: If we do not make progress on moving WebVTT to
>>    Recommendation in this Charter period we do not intend to
>>    include it on any rechartering.
>>
>>    thierry: That's a final step - I think we should be aiming to
>>    move to CR well before that.
>>
>>    david: I agree.
>>
>>    glenn: We could publish it as a WG Note, to make it easier for
>>    external people to reference.
>>
>>    nigel: This is a lot easier.
>>
>>    thierry: That would probably be a final step to that work.
>>
>>    nigel: In fact publishing a Note is a process requirement if we
>>    stop working on it.
>>
>>    thierry: We would do that if we removed it from the Charter.
>>
>>    glenn: It would be helpful to have a document that does not
>>    have the word "Draft" in it.
>>
>>    thierry: I'm happy to help with the wide review; that's one
>>    thing. The second thing is the CR.
>>    ... We could stay in CR for a couple of years and monitor
>>    implementation work, or we could
>>    ... remove non-implemented features. Right now there are a lot
>>    of features that are not
>>    ... implemented. That's something we could do in parallel.
>>    Maybe it is not useful to have
>>    ... comments on features that we are likely to drop.
>>
>>    nigel: I want to signal that if we have to drop features that
>>    are essential for accessibility then
>>    ... I will have to object to it progressing.
>>
>>    thierry: There's also a lack of specification text on
>>    integrating CSS. We could maybe save time
>>    ... by not addressing issues that we know are unlikely to be
>>    implemented in the next two years.
>>
>>    group: discussion about who is interested in contributing to
>>    implementation work etc and therefore progressing responses to
>>    comments.
>>
>>    RESOLUTION: If we do not move WebVTT to CR in this Charter
>>    period then we will not include it in any new Charter.
>>
>>    andreas: We could mention the TTML to WebVTT mapping document
>>    in the Web & TV IG meeting.
>>    ... We published it last year and are awaiting implementation
>>    comments. We are waiting for a
>>    ... stable reference for WebVTT in order to proceed.
>>
>>    thierry: You would expect to see at least a CR document?
>>
>>    andreas: CR would clearly indicate a stable set of features you
>>    can map against.
>>
>> Tagging
>>
>>    david: DASH and the MP4 file format have a way to tag the kind
>>    of role of a track, using a URI
>>    ... to identify the vocabulary used, and then a term from that
>>    vocabulary. I need a URI to
>>    ... refer to the @kind vocabulary in the HTML5 specification,
>>    and there isn't one.
>>
>>    pierre: There is one but it is not complete, specified in DASH.
>>
>>    david: It is not specified in the HTML document itself.
>>
>>    pierre: That's correct. As long as we can reference the one in
>>    DASH that can be used.
>>
>>    david: Agreed there is a DASH vocabulary.
>>
>>    pierre: So the request to add one to HTML is not required for
>>    MPEG CMAF because the DASH one can be used.
>>
>>    david: I got agreement from WHATWG and the Web Platform WG for
>>    about:html-kind as the URI
>>    ... that refers to the @kind vocabulary in the HTML
>>    specification.
>>    ... And I have registered that with IANA.
>>    ... I'm waiting for that URI to appear in a revision of the Web
>>    Platform docs. When it is then
>>    ... I will update the IANA form.
>>
>>    nigel: It's good to have that but I would note that in my view
>>    the kind vocabulary is terrible.
>>
>>    glenn: There are some semantics associated, such as prevention
>>    of display of metadata tracks by the UA.
>>
>>    david: I would agree that the HTML vocabulary is both under-
>>    and over-specified simultaneously! (in different ways)
>>
>>    nigel: In my view it is insufficiently rich to describe the
>>    purpose and intent of the track data.
>>
>>    pierre: It would be great if as making the HTML vocabulary more
>>    official we could also fix it.
>>
>>    david: I support that.
>>    ... CMAF does prefer DASH at the moment - it says to use the
>>    DASH term if it supports what you want to do.
>>
>>    nigel: I also note that we have not addressed how to extract
>>    something equivalent to kind
>>    ... within a timed text document so that it can be extracted
>>    and used to embed into a host HTML page.
>>    ... We did address language recently, but not kind.
>>
>>    david: Some people want to manage external manifest files, but
>>    I'm in favour of self describing documents.
>>    ... I'm also aware of ongoing discussions about tags for easy
>>    to read captions (mandated by FCC) and karaoke.
>>
>>    pierre: There is a very specific definition of those two terms
>>    in karaoke.
>>
>>    glenn: In TTML2 we have a named metadata item for easy reader.
>>    There's nothing on karaoke per se.
>>    ... nothing that uses that term in TTML2.
>>
>>    nigel: [adjourns for a break] - let's meet in Auditorium IV at
>>    1100 for our update to Web & TV IG.
>>
>>    <nigel_> nigel: Joint meeting - see #webtv
>>
>> TTML1 Errata
>>
>>    nigel: Are there any other errata other than for backgrounds on
>>    spans and lines?
>>
>>    pierre: The only thing I'd mention is that the computed style
>>    resolution for % is very well defined
>>    ... but the computed style for em is not so clear when you say
>>    e.g. tts:fontSize="2em" but
>>    ... that is with respect to the current font size but that is
>>    not well defined in TTML1. I assume
>>    ... it is relative to the parent element's font size but it
>>    does not say that clearly.
>>
>>    glenn: I would consult TTML1 and then go back and reference
>>    XSL-FO which would take me
>>    ... to CSS2. Without having done a recent review of that I
>>    don't know off the top of my head
>>    ... but I'm pretty sure you're right - it would have to make
>>    use of the computed font size of
>>    ... the parent element.
>>
>>    pierre: Notice that we already have issue #206 on the ttml1
>>    repo which is a bug about
>>    ... specifying em units for fontSize on region.
>>
>>    nigel: That sounds very similar.
>>
>>    glenn: Right now there are 23 open issues on TTML1 so I would
>>    expect that there are some
>>    ... errata to be written for those and they probably also need
>>    to be fixed in TTML 2 also.
>>
>>    pierre: I can go ahead and create an issue for this.
>>
>>    glenn: Go ahead - also refer to #206 - it may be related but
>>    more general.
>>    ... I think I propose that it should be in relation to 1c.
>>
>>    pierre: That was my first thought, but looking at XSL-FO I
>>    think it is probably more like %.
>>
>>    nigel: Okay, so the one on the agenda is:
>>    [20]https://github.com/w3c/ttml1/issues/209
>>
>>      [20] https://github.com/w3c/ttml1/issues/209
>>
>>    andreas: I think there has not been much progress since we last
>>    discussed it. We said we need
>>    ... more investigation to find a good solution. I want to point
>>    to something related.
>>    ... This problem about gaps between lines has been addressed by
>>    the HbbTV 2.0.1 spec
>>    ... which a lot of televisions will implement. At the moment
>>    that is not really interoperable
>>    ... and compatible with IMSC 1 so we should pay attention to
>>    it.
>>    ... References spec text from HbbTV 2.0.1 that, specific to
>>    EBU-TT-D 1.0 defines that
>>    ... where the lineHeight is "normal" or <125% the background of
>>    each generated inline area
>>    ... shall be rendered such that there are no gaps between the
>>    rendered backgrounds of
>>    ... adjacent lines.
>>
>>    glenn: We have a quasi default of doing what CSS does, which is
>>    different from what this suggests.
>>    ... This mandates behaviour that is at variance with the XSL-FO
>>    and CSS behaviour.
>>
>>    andreas: Yes.
>>
>>    glenn: By the way issue #209 on the TTML spec has a length
>>    discussion on this.
>>    ... The bottom line in my reading is that the height of an
>>    inline area in CSS is implementation defined.
>>    ... Different implementations have fine tuned themselves to be
>>    consistent with each other, outside of any spec.
>>
>>    nigel: You can see an editorial requirement example of this at
>>    [21]http://bbc.github.io/subtitle-guidelines/#Background-size
>>
>>      [21] http://bbc.github.io/subtitle-guidelines/#Background-size
>>
>>    glenn: I agree that we need to nail this down - also see issue
>>    #212 in TTML1.
>>
>>    nigel: [22]https://github.com/w3c/ttml1/issues/212
>>    ... [23]https://github.com/w3c/ttml1/issues/209
>>
>>      [22] https://github.com/w3c/ttml1/issues/212
>>      [23] https://github.com/w3c/ttml1/issues/209
>>
>>    pierre: A browser based CSS implementation would display a gap?
>>
>>    glenn: Correct
>>
>>    andreas: There are scripting techniques for getting around
>>    this.
>>
>>    pierre: If we feel this is a common requirement for
>>    accessibility then it needs to be addressed in the CSS WG
>>
>>    glenn: I've had a detailed offline discussion with Bert Bos
>>    about this and he pointed out that
>>    ... one of the advanced level 4 modules might at some point be
>>    able to deal with this.
>>    ... There are a whole bunch of assumptions in CSS on inline
>>    non-replaceable areas, for example
>>    ... you cannot specify the content height manually. The height
>>    property explicitly does not
>>    ... apply. That was the first problem we ran into, because we
>>    wanted the height of the content
>>    ... box to extend to the line area. Somewhere I proposed a mode
>>    for the style engine to use
>>    ... different semantics for the height of content areas. The
>>    question is can you have a profile
>>    ... that defaults the parameter to a particular value.
>>
>>    nigel: The pressing need here is to issue some statement on
>>    this for TTML1.
>>
>>    piere: I recall that some people use a style where they do
>>    actually want the gap.
>>
>>    andreas: yes, for example if you have the lineheight at 200%
>>    you don't want such a big background area.
>>
>>    pierre: In CSS can you always add padding to every line?
>>
>>    glenn: You can but the problem is you cannot determine at
>>    authoring time what value to add.
>>    ... At first order we should document more carefully what the
>>    current situation is in TTML1.
>>    ... That may allow people to come up with no-gap semantics. We
>>    could define the default
>>    ... semantics to be the no-gap scenario but if we do that we
>>    need to allow the author to define
>>    ... the other behaviour. If we change the default now what
>>    would that break?
>>
>>    nigel: I understand that the content rectangle is not well
>>    defined?
>>
>>    glenn: It is not, but all the browser implementations do it
>>    roughly the same way.
>>
>>    nigel: Could we add an informative note via an erratum to say
>>    that the content rectangle is
>>    ... not well defined but is commonly implemented so that it
>>    does not go to the line height?
>>
>>    pierre: That's not what I'm hearing. I think CSS needs to
>>    address this.
>>
>>    glenn: I'm worried that we cannot easily go back and
>>    retroactively define the content height
>>    ... to never show a gap.
>>
>>    pierre: It would be easier to do that if it were not that some
>>    folk like the gap.
>>
>>    glenn: In TTML2 we can add a new mode that drives that, but in
>>    TTML1 what can we do?
>>
>>    andreas: This requirement for no gaps came from accessibility
>>    guidelines to get proper presentation.
>>    ... The minimum we could say is that some specifications could
>>    define this.
>>
>>    pierre: If someone is overriding that rendering it needs to be
>>    flagged.
>>
>>    andreas: That will not change, I think this is more of an
>>    interoperability problem.
>>    ... There is an initial step e.g. for an IMSC 1.1, and then a
>>    long term TTML2 solution.
>>    ... For now we should say something about this in TTML1.
>>
>>    pierre: +1
>>
>>    andreas: I would also hope for a liaison to respond to this.
>>
>>    glenn: We can note that the algorithm for content height is not
>>    concretely defined and that
>>    ... browsers do behave the same with current CSS
>>    implementations and will introduce a gap.
>>    ... If we do want a new TTML1 feature we could write a short
>>    specification introducing a
>>    ... ttsx namespace style that is interpreted in a particular
>>    way.
>>
>>    andreas: Ideally if there is a proper parameter to control this
>>    it should be defined in this group.
>>
>>    nigel: +1
>>
>>    glenn: That would be an official extension to TTML1, which we
>>    could say maps to a particular
>>    ... syntax and semantic in TTML2.
>>    ... That might be an approach.
>>
>>    pierre: If there is an urgent need to address real problems we
>>    should address it in IMSC 1.1.
>>
>>    glenn: I've heard 3 things: 1. Clarify TTML1 with an errata -
>>    we can do that non-controversially.
>>    ... 2. We can define new mechanisms in TTML2 - we can do that
>>    no problem.
>>    ... 3. More controversially, define a new extension style for
>>    TTML1. That creates another fork
>>    ... in the implementation space.
>>
>>    andreas: The target when this was discussed was an IMSC 1.1
>>    version. If that is possible we
>>    ... should do that.
>>
>>    pierre: Absolutely. The question is if there is an urgent need
>>    to resolve an industry problem now.
>>    ... The worst thing would be to make a change that does not
>>    solve the problem.
>>
>>    andreas: HbbTV has solved this for now - it would be
>>    interesting to know if this breaks
>>    ... current implementations.
>>
>>    pierre: it would be good to have a formal communication with
>>    HbbTV about this issue.
>>    ... It is essential that HbbTV is encouraged to communicate
>>    their requirements to this group and we should be welcoming of
>>    this, even if we make the initial communication.
>>
>>    andreas: We should also be clear that it is needed for
>>    interoperability to establish this communication channel.
>>
>>    nigel: Notes that independent of HbbTV the BBC raised this
>>    issue on TTML2 and andreas opened the equivalent on TTML1.
>>    ... I want to come back to what we can do here.
>>
>>    andreas: There's the formal comms with HbbTV, an errata for
>>    TTML1, and a discussion about
>>    ... how to fix for TTML2. If there is no formal requirement for
>>    this then it will not happen in IMSC 1.
>>
>>    pierre: BBC has raised this for TTML2, but the timescale for
>>    that is very different than for TTML1.
>>    ... To make a change on TTML1 requires a higher threshold, so
>>    if there is a group such as
>>    ... HbbTV that needs this in the short term then we should do
>>    it.
>>
>>    <scribe> ACTION: nigel Draft a liaison to HbbTV requesting
>>    further information and proposing an option e.g. to extend IMSC
>>    1 to allow signalling of background height on span, and request
>>    timelines etc. [recorded in
>>    [24]http://www.w3.org/2016/09/19-tt-minutes.html#action01]
>>
>>      [24] http://www.w3.org/2016/09/19-tt-minutes.html#action01]
>>
>>    <trackbot> Created ACTION-478 - Draft a liaison to hbbtv
>>    requesting further information and proposing an option e.g. to
>>    extend imsc 1 to allow signalling of background height on span,
>>    and request timelines etc. [on Nigel Megitt - due 2016-09-26].
>>
>>    nigel: Okay, that works; I would also still like to see the
>>    erratum on TTML1 to provide the context
>>    ... for any update to IMSC 1 to allow signalling this
>>    behaviour.
>>
>>    glenn: I have added a comment on the issue at
>>    [25]https://github.com/w3c/ttml1/issues/209#issuecomment-247973
>>    673
>>
>>      [25] https://github.com/w3c/ttml1/issues/209#issuecomment-247973673
>>
>>    nigel: Thank you!
>>
>>    glenn: Of course that doesn't explain what to do about it, but
>>    that's for [26]https://github.com/w3c/ttml2/issues/150
>>    ... We have consensus in TTLM2 to solve this?
>>
>>      [26] https://github.com/w3c/ttml2/issues/150
>>
>>    nigel: Yes please!
>>
>>    glenn: I have a bpd content proposal where I define 7 possible
>>    values.
>>
>>    nigel: That may be more than we need - let's review.
>>    ... Thanks for the good discussion everyone, let's adjourn for
>>    lunch and return at 1400.
>>
>> TTML2 Pull Requests
>>
>>    nigel: First up, [27]https://github.com/w3c/ttml2/pull/177 Add
>>    tts:background{Clip,Extent,Origin}
>>
>>      [27] https://github.com/w3c/ttml2/pull/177
>>
>>    glenn: This is for image rendering support - I missed a couple
>>    of items from CSS: there is
>>    ... an editorial note to add them.
>>    ... I ended up using backgroundExtent rather than
>>    backgroundSize for consistency.
>>
>>    nigel: Just a note on reviewing the PRs - they don't include
>>    the built HTML so it's hard to
>>    ... review or diff. I'd like a CI tool to build the HTML
>>    automatically so we can review it.
>>
>>    glenn: I could do the build and check in the built HTML but
>>    then on pulling I would have to
>>    ... remove it and build it again for gh-pages.
>>    ... I'll go ahead and make a change to make these easier to
>>    review.
>>
>>    <glenn>
>>    [28]https://www.w3.org/TR/css3-background/#the-background-origi
>>    n
>>
>>      [28] https://www.w3.org/TR/css3-background/#the-background-origin
>>
>>    nigel: So now we have backgroundOrigin as well as
>>    backgroundPosition?
>>
>>    glenn: We may want to rename these!
>>
>>    nigel: (notes that this looks analogous to origin and position
>>    but is not)
>>
>>    glenn: backgroundOrigin defines where the background is drawn
>>    relative to the content.
>>    ... This is as defined in CSS3 backgrounds and borders - it's
>>    the same semantic.
>>    ... I took off the -box suffix that's on CSS3.
>>
>>    nigel: I sense that there are some changes needed here to clear
>>    up the names and make them
>>    ... less potentially confusing. Also I'd encourage review of
>>    this in the context of IMSC 2
>>    ... if we want to support image placement in more detail.
>>
>>    pierre: This does not express how you would use SMPTE
>>    background image in IMSC 1.
>>
>>    glenn: That's actually mapped to the image element.
>>
>>    pierre: yes.
>>
>>    glenn: However we did define background image also in TTML2 and
>>    these attributes
>>    ... I believe fully define the semantics for background images.
>>    ... In the case of a foreground image these don't come up
>>    because they define the content
>>    ... rectangle. There's never a box in which to position it -
>>    that only applies when the image
>>    ... is used for the background. Also bear in mind that
>>    background images may be repeated
>>    ... in x and y directions, which can never happen with
>>    foreground images.
>>    ... For foreground image size you would use bpd and ipd rather
>>    than backgroundExtent.
>>    ... I need to think if it would ever be applicable to have the
>>    same semantic as backgroundExtent
>>    ... on a foreground image. I want to see if CSS allows that
>>    property on the image element
>>    ... in HTML and what does it mean.
>>
>>    nigel: Just considering the use cases for this - one that comes
>>    to mind is the use of a
>>    ... graduated fill background image that is animated to move
>>    along behind foreground text
>>    ... for karaoke usage. Do these semantics support that?
>>
>>    glenn: Yes I think you could animate the x and y positions,
>>    either discretely or continuous.
>>
>>    nigel: The conclusions for the time being are 1) that more
>>    thinking is needed for the names
>>    ... and 2) whether backgroundExtent can apply to foreground
>>    images.
>>    ... For the hard of thinking, some example images etc would
>>    really help, since the terminology
>>    ... has a lot of repetition that makes it hard to understand
>>    the differences.
>>    ... I've added some notes to the issue.
>>    ... Moving on to Add support for rounded borders by introducing
>>    <border-radii> compone…
>>    ... [29]https://github.com/w3c/ttml2/pull/179
>>
>>      [29] https://github.com/w3c/ttml2/pull/179
>>
>>    nigel_and_glenn: [discussion of single value processor
>>    semantics for border radii without consensus emerging]
>>
>>    glenn: The more interesting case is the one raised in the issue
>>    [30]https://github.com/w3c/ttml2/issues/176
>>
>>      [30] https://github.com/w3c/ttml2/issues/176
>>
>>    nigel: explains images in issue
>>
>>    glenn: I would suggest an optional token for this and a default
>>    behaviour in case nothing is specified.
>>    ... We also have to set up some context for when it might apply
>>    - it would not apply when
>>    ... all the line areas are the same length - you are proposing
>>    a process for merging the
>>    ... background areas.
>>
>>    nigel: Yes
>>
>>    glenn: Would you allow me to merge this PR and address your
>>    issue as a later iteration?
>>
>>    nigel: Yes, that allows progress.
>>
>>    glenn: I agree with the issue - I might consult others in CSS
>>    land for their opinions too.
>>    ... It may even be in background and borders 4, I need to check
>>    ... How to specify merged background areas with radii when
>>    there is no corner is harder
>>    ... to specify - I'm sure it's possible but it requires a bit
>>    of thought.
>>
>>    nigel: Agreed!
>>    ... Okay, next one is Add missing two component expression to
>>    <position> value syntax.
>>    [31]https://github.com/w3c/ttml2/pull/180
>>    ... I added a comment about the ambiguity here.
>>
>>      [31] https://github.com/w3c/ttml2/pull/180
>>
>>    glenn: The ambiguity is resolved by the two value to four value
>>    mapping tables.
>>    ... The last entry is ambiguous I agree since it does not
>>    distinguish the lengths
>>
>>    nigel: Even if this is normative and clear I would prefer at
>>    least note to point people at the
>>    ... order preference.
>>
>>    glenn: I'll see what I can do while I'm also dealing with the
>>    last line in the table.
>>
>>    nigel: Let's take a break - back here at 1545
>>    ... Next is Remove cea{608,708} prefix from named items.
>>    [32]https://github.com/w3c/ttml2/pull/182
>>
>>      [32] https://github.com/w3c/ttml2/pull/182
>>
>>    glenn: I had the same question in my mind as Nigel, whether or
>>    not any of the deprefixed
>>    ... names had any similarity to the non-prefixed name. The
>>    programName and programType
>>    ... seem to be likely, the others not.
>>    ... The ones that had cea prefixes need to be syntactically
>>    compatible with SMPTE-TT.
>>    ... I can not simply remove the reference to 608 or 708 from
>>    the definition of them without
>>    ... sacrificing syntactic specificity.
>>
>>    nigel: And there's an editorial task to add the source
>>    definitions?
>>
>>    glenn: That's right.
>>    ... I'm pretty sure that programName is just a string and no
>>    more restricted. The originalProgrammeTitle
>>    ... is probably the same semantic.
>>    ... We also need to check with Mike Dolan since he was involved
>>    in defining these in
>>    ... SMPTE-TT. I think we should be able to merge programName
>>    and originalProgramTitle
>>    ... probably. We have to choose which token to end up with - I
>>    don't have a strong preference.
>>    ... My preference is to add a prefix back, but just make it cea
>>    or cta (remove the 608 or 708)
>>    ... and we could add it for EBU also.
>>
>>    nigel: An observation here is that building the named items
>>    into the TTML2 spec gives us a
>>    ... potential problem in that it makes it harder to update the
>>    list later. A common pattern
>>    ... is to reference an external list or classification scheme
>>    which can be updated independently.
>>    ... Since none of these named items normatively affects
>>    processing this should be okay.
>>    ... This is a bit like the role registry approach in TTML1.
>>
>>    glenn: In TTML1 we had a requirement to prefer Dublin Core, and
>>    after much debate we took
>>    ... a minimalist approach and hardly defined anything. Then
>>    SMPTE-TT came along and defined
>>    ... a whole bunch of metadata items for 608 and 708 that were
>>    thought to be important.
>>    ... Since one of the nominal driving factors for TTML2 is to
>>    support all the extensions in
>>    ... SMPTE-TT we ended up adding these in.
>>
>>    andreas: I think the most practical solution is to reference a
>>    document that we maintain that
>>    ... defines our unqualified namespace items and informatively
>>    links to other sources of
>>    ... namespace qualified items in other organisations'
>>    namespaces.
>>
>>    glenn: That sounds like a plan.
>>
>>    nigel: Same here.
>>
>>    glenn: I think we should leave in usesForced and
>>    alternativeText
>>
>>    nigel: Even those we do not need to be in the specification
>>
>>    glenn: I think we want to refer to them elsewhere in the spec
>>    so I'd like to keep those two
>>    ... unqualified names in the spec.
>>
>>    andreas: Ok, if they depend on these.
>>
>>    glenn: Others that we have not defined yet we can bind to a
>>    namespace and offer a template
>>    ... for the future to define new named items.
>>    ... That would simplify this work quite a bit.
>>    ... I'll add a note to the issue with that plan.
>>    ... I didn't abbreviate alt text so I had it as alternateText -
>>    what's the view?
>>
>>    pierre: Keep it as close as possible to IMSC 1.
>>
>>    nigel: yes, happy with altText.
>>
>>    glenn: ok
>>
>>    nigel: We have essentially covered Add alternateText named
>>    metadata item (#107). [33]https://github.com/w3c/ttml2/pull/183
>>
>>      [33] https://github.com/w3c/ttml2/pull/183
>>
>> IMSC 2
>>
>>    pierre: We are beginning to get industry feedback from IMSC 1
>>    implementation.
>>
>>    nigel: There seem to be some preconceptions in the wild about
>>    what IMSC 2 will be. I'd like
>>    ... us to collate requirements.
>>
>>    pierre: I would happily collate requirements for IMSC 2.
>>
>>    glenn: I think there will be a continuing requirement for
>>    images to deal with internationalisation
>>    ... cases that not all clients will be able to support.
>>
>>    <scribe> ACTION: pal Refactor the IMSC repository in
>>    preparation for future versions of IMSC. [recorded in
>>    [34]http://www.w3.org/2016/09/19-tt-minutes.html#action02]
>>
>>      [34] http://www.w3.org/2016/09/19-tt-minutes.html#action02]
>>
>>    <trackbot> Created ACTION-479 - Refactor the imsc repository in
>>    preparation for future versions of imsc. [on Pierre-Anthony
>>    Lemieux - due 2016-09-26].
>>
>>    glenn: Having them in one repository helps with issue tracking
>>    but you should use labels of
>>    ... some kind to distinguish between the different versions.
>>
>>    pal: At the root will be a roadmap document for all the
>>    versions of IMSC.
>>    ... As soon as I get requirements for IMSC 2 I will start a
>>    requirements document too.
>>
>>    nigel: It's not from BBC but Ruby seems obvious.
>>
>>    pierre: Yes I hear that a lot, also HDR and tate chu yuko.
>>    Disparity is another one.
>>
>>    nigel: Also Wide Color Gamut?
>>
>>    pierre: Yes. Also background area between lines.
>>
>>    nigel: I would add the safe crop area stuff too.
>>
>>    andreas: As well as asking for requirements it would be good to
>>    ask for the use case and the
>>    ... problem that needs to be solved, in some detail.
>>
>>    pierre: So yes, HDR, all east asian layout.
>>
>>    rohit: Any mention of the condition attribute?
>>
>>    pierre: No not yet. I've heard people wanting to do responsive
>>    design, but I'm not sure we're there yet.
>>
>>    nigel: What about continuous animation?
>>
>>    pierre: Not yet.
>>
>>    nigel: Seems strange to me based on historical BBC research to
>>    have disparity but not continuous animation.
>>
>>    andreas: We should check what east asian organisations need to
>>    do.
>>
>>    dae: I'd like to know if there are any parts of TTML2 that folk
>>    think might need to change. Ruby for example?
>>
>>    pierre: I'd like to be really specific about all the Ruby
>>    features in a pedantic way.
>>
>>    glenn: All the TTML2 layout features were driven from existing
>>    content in lambda cap. it is
>>    ... easy to say what was not driven from lambda cap.
>>    ... It is easy to enumerate all the different Ruby features -
>>    look at TTML2 from
>>    ... §10.2.30 tts:ruby to §10.2.37 tts:rubyPreserve also
>>    §10.2.40 tts:textCombine
>>    ... §10.2.41 tts:textEmphasis and §10.2.43 tts:textOrientation.
>>    ... All those were directly driven by lambda cap. There are a
>>    couple that were not:
>>    ... rubyOverflow, rubyOverhand and rubyOverhangClass.
>>
>>    rohit: Also rubyReserve?
>>
>>    glenn: Yes. Overflow and overhang came out of the Japanese
>>    requirements as well as how
>>    ... to handle some cases that were not obvious.
>>
>>    pierre: Thanks!
>>
>>    nigel: Do we have feature designators for these yet?
>>
>>    glenn: There's an editorial note in E.1 for adding those.
>>
>>    group: [discussion of structure of specification, areas of
>>    TTML2 that may be relatively more 'risky', how to make progress
>>    etc.]
>>
>>    dae: Can we revisit the initial construct in TTML2 tomorrow?
>>
>> Agenda bash
>>
>>    group: plans ahead for tomorrow, updates agenda.
>>
>> TTML2 implementation work
>>
>>    glenn: Skynav's TTT set of tools could be viewed as 1-3
>>    implementations. It's a layered
>>    ... system - the validation layer at the bottom could be
>>    considered a transformation implementation.
>>    ... TTX above that has one module that translates into an ISD
>>    sequence. For example it can
>>    ... take IMSC1 or SMPTE-TT documents and turn them into TTML2
>>    ISDs. Then the next
>>    ... layer is TTPE that implements formatting semantics.
>>
>>    rohit: At Netflix we are building a TTML2 oriented pipeline.
>>    The idea is to take TTML2 source
>>    ... documents, convert them into a canonical form (probably
>>    TTML2 ISD) and then use them
>>    ... to generate output formats including WebVTT and rendered
>>    subtitles.
>>    ... Depending on the test vector set for TTML2 Netflix may be
>>    able to meet 40-50% of the
>>    ... tests for implementation.
>>
>>    glenn: I'd also like to add: in terms of presentation semantics
>>    implementation in TTPE for
>>    ... TTML2 features, the only new features it does not yet
>>    support are the use of referenced
>>    ... external fonts, audio and disparity. Everything else that's
>>    new in TTML2 it supports already
>>    ... from a presentation semantic. There might be some fine
>>    points to some of the features
>>    ... that we are still tweaking. We have test content for all of
>>    those features that we are using
>>    ... to generate presentable output in either images or SVG. So
>>    we are way ahead on implementation
>>    ... of presentation and we have test content for most all of
>>    it. Our schedule for finishing
>>    ... implementation work on TTML2 is scheduled to be finished
>>    early March 2017.
>>
>>    thierry: The horizontal review groups request review
>>    opportunity as soon as possible.
>>
>>    nigel: In fact I should trigger that process straight away.
>>    ... Wide review is even wider than that.
>>
>>    thierry: We should start to initiate that to make sure there is
>>    enough time.
>>
>>    glenn: I'd like to have a version ready for a new WD by early
>>    October.
>>
>>    thierry: Remember that we can limit the scope of review only to
>>    the additional features in
>>    ... TTML2 that are new relative to TTML1.
>>
>>    pierre: Remember also for wide review you have to factor in
>>    time to respond to comments.
>>    ... For the east Asian text layout there's an action to contact
>>    ARIB specifically.
>>
>>    nigel: We will also need horizontal review. As a minimum I
>>    should contact the horizontal review groups and request time on
>>    their schedule for a new document early November.
>>
>>    <scribe> ACTION: nigel Request schedule time for horizontal
>>    review of TTML2 [recorded in
>>    [35]http://www.w3.org/2016/09/19-tt-minutes.html#action03]
>>
>>      [35] http://www.w3.org/2016/09/19-tt-minutes.html#action03]
>>
>>    <trackbot> Created ACTION-480 - Request schedule time for
>>    horizontal review of ttml2 [on Nigel Megitt - due 2016-09-26].
>>
>>    glenn: Why don't I give you a list of new features to start
>>    reviewing?
>>
>>    nigel: Good idea.
>>
>>    <scribe> ACTION: gadams Provide nigel with a list of new
>>    features in TTML2 to begin reviewing [recorded in
>>    [36]http://www.w3.org/2016/09/19-tt-minutes.html#action04]
>>
>>      [36] http://www.w3.org/2016/09/19-tt-minutes.html#action04]
>>
>>    <trackbot> Created ACTION-481 - Provide nigel with a list of
>>    new features in ttml2 to begin reviewing [on Glenn Adams - due
>>    2016-09-26].
>>
>>    glenn: How would it be if we have a solid working draft for
>>    wide review by Nov 1?
>>
>>    nigel: Sounds good to me.
>>
>>    glenn: And how about moving to CR by the end of the year?
>>
>>    nigel: It's ambitious but we can try.
>>    ... Looking at the picture on
>>    [37]https://www.w3.org/wiki/TimedText/Publications it shows
>>    ... a FPWD of IMSC 2 back in June, but I think from today we
>>    have decided to collate
>>    ... industry requirements and then maybe base it on the TTML2
>>    CR perhaps?
>>
>>      [37] https://www.w3.org/wiki/TimedText/Publications
>>
>>    pierre: We should aim to make IMSC 2 based solely on industry
>>    requirements but we can
>>    ... certainly set a new date - I'm comfortable with that,
>>    partly as a challenge to folk who
>>    ... want IMSC 2 - we need to get going on it.
>>
>>    nigel: Agreed. Shall we say IMSC 2 FPWD by Dec 1?
>>
>>    pierre: Sounds great to me, maybe even earlier.
>>
>>    nigel: Ok let's leave it at that for now and if we can make it
>>    earlier, great.
>>
>>    dae: Can an implementation satisfy both TTML2 and IMSC 2?
>>
>>    nigel: Yes.
>>    ... Ok we're out of time for today, thanks all. Time to adjourn
>>    for tomorrow.
>>
>>    andreas: Can we make sure we cover IMSC 1 implementation work
>>    tomorrow?
>>
>>    nigel: yes let's do that.
>>    ... [adjourns meeting]
>>
>> Summary of Action Items
>>
>>    [NEW] ACTION: gadams Provide nigel with a list of new features
>>    in TTML2 to begin reviewing [recorded in
>>    [38]http://www.w3.org/2016/09/19-tt-minutes.html#action04]
>>    [NEW] ACTION: nigel Draft a liaison to HbbTV requesting further
>>    information and proposing an option e.g. to extend IMSC 1 to
>>    allow signalling of background height on span, and request
>>    timelines etc. [recorded in
>>    [39]http://www.w3.org/2016/09/19-tt-minutes.html#action01]
>>    [NEW] ACTION: nigel Request schedule time for horizontal review
>>    of TTML2 [recorded in
>>    [40]http://www.w3.org/2016/09/19-tt-minutes.html#action03]
>>    [NEW] ACTION: pal Refactor the IMSC repository in preparation
>>    for future versions of IMSC. [recorded in
>>    [41]http://www.w3.org/2016/09/19-tt-minutes.html#action02]
>>
>>      [38] http://www.w3.org/2016/09/19-tt-minutes.html#action04
>>      [39] http://www.w3.org/2016/09/19-tt-minutes.html#action01
>>      [40] http://www.w3.org/2016/09/19-tt-minutes.html#action03
>>      [41] http://www.w3.org/2016/09/19-tt-minutes.html#action02
>>
>> Summary of Resolutions
>>
>>     1. [42]If we do not move WebVTT to CR in this Charter period
>>        then we will not include it in any new Charter.
>>
>>    [End of minutes]
>>      __________________________________________________________
>>
>>
>>     Minutes formatted by David Booth's [43]scribe.perl version
>>     1.144 ([44]CVS log)
>>     $Date: 2016/09/19 17:25:20 $
>>
>>      [43] http://dev.w3.org/cvsweb/~checkout~/2002/scribe/scribedoc.htm
>>      [44] http://dev.w3.org/cvsweb/2002/scribe/
>>
>>
>>
>> *--*
>>
>>
>> *Nigel Megitt*
>>
>> Executive Product Manager, BBC Design & Engineering
>>
>> Telephone : +44 (0)3030807996
>>
>> BC2 C1 Broadcast Centre, Media Village, 201 Wood Lane, London W12 7TP
>>
>>
>>
Received on Monday, 19 September 2016 20:51:25 UTC

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