- From: Nigel Megitt <nigel.megitt@bbc.co.uk>
- Date: Thu, 29 Nov 2018 16:34:18 +0000
- To: Timed Text Working Group <public-tt@w3.org>
- Message-ID: <5941EAB8802D6745A7D363D7B37BD1F79338F6E4@bgb01xud1012>
Thanks all for attending today's TTWG meeting. Minutes can be found in HTML format at https://www.w3.org/2018/11/29-tt-minutes.html
In text format:
[1]W3C
[1] http://www.w3.org/
Timed Text Working Group Teleconference
29 Nov 2018
See also: [2]IRC log
[2] https://www.w3.org/2018/11/29-tt-irc
Attendees
Present
Andreas, Cyril, Gary, Glenn, Pierre, Thierry, Nigel
Regrets
none
Chair
Nigel
Scribe
nigel
Contents
* [3]Topics
1. [4]This meeting
2. [5]TTML Profile Registry Actions, Pull Requests and
Issues
3. [6]TTWG Future requirements
4. [7]Add generic CSS property functionality tt-reqs#2
5. [8]f2f meeting and Joint f2f meeting with EBU Timed
Text, Feb 1 2019
6. [9]CSS Actions Review
7. [10]WebVTT
8. [11]AD Community Group
9. [12]Meeting close
* [13]Summary of Action Items
* [14]Summary of Resolutions
__________________________________________________________
<inserted> scribe: nigel
This meeting
Nigel: Apologies for the late start today.
... Our agenda today is at
[15]https://github.com/w3c/ttwg/issues/6
... [iterates through agenda]. Any other business or particular
points to raise?
[15] https://github.com/w3c/ttwg/issues/6
Pierre: It might be too late, but we have this plan for
requirements, but have not formally informed other
organisations
... who have cared in the past. I think the announcement was
public so we can point people to it but maybe we ought
... to at least alert SMPTE, EBU. SMPTE meets next week. I
wonder if a really quick liaison might be worth it, later today
... or tomorrow, saying we're gathering requirements, see this
email for detail. For discussion if there's time.
Nigel: Thanks, that's a really good point.
... Anything else for the agenda?
group: [silence]
TTML Profile Registry Actions, Pull Requests and Issues
Nigel: I don't think there's anything to discuss here, I did
give Glenn the prod he requested.
Glenn: I just got back from travelling and am catching up, I'm
afraid I'm behind on this but will push on this next week.
Nigel: Okay.
TTWG Future requirements
Nigel: Pierre's comment above relates to this agenda item.
... I'm happy to draft something lightweight and send it out
tomorrow, it's a good point.
... Organisations who should receive it are, off the top of my
head, SMPTE, EBU. DVB, ATSC, HbbTV, ARIB. Any others?
... I will also check the liaisons page.
Andreas: I just wanted to comment that my colleague Peter tho
Pesch recently added two issues in the requirements
... repository of the XR Community Group on subtitles,
especially on requirements for 360ยบ videos.
... He will send the link to the issues. This is a good place
to discuss what could also be covered in a future version TTML.
Nigel: Thanks that sounds good, if you could ask Peter to raise
at least one issue on tt-reqs so we can track that please?
Glenn: I'm wondering if it's worth discussing what are ground
rules are for, say, TTML2 2nd Ed vs a new version of TTML,
... e.g. TTML3 in particular whether or not we are considering
new features in TTML2 2nd Ed or if we are considering
... those only for TTML3. In other words is TTML2 2nd Ed just
bug fixes or are we going to try to slot new features there.
... We haven't discussed this yet. I don't know if we need to
discuss it right now.
Nigel: A quick response on that: first let's gather the
requirements and then work out how we're going to deliver them.
... I think this is one of the agenda topics for our face to
face meeting.
... We said we wouldn't work this out immediately.
Glenn: I'm comfortable with that.
... The only reason I mention it is because as I try to
incorporate requirements into the draft requirements document I
... need to frame them somehow. I can delay doing that for the
time being.
Nigel: Sounds good.
Add generic CSS property functionality tt-reqs#2
Nigel: (I haven't updated github-bot with the tt-reqs repo yet)
... The discussion here is about if we should only add specific
known CSS properties into TTML or one of its profiles or
... if we should do as the issue requests which is to allow for
generic CSS properties to be specified in document instances.
... The point here is that there's a class of use cases where
waiting for new CSS properties to be added to the spec on an
... annual cycle isn't feasible.
Pierre: That's a good point. I think in this case the way to do
it is to create attributes in foreign namespaces so folks
... can experiment to their hearts' content.
... A new feature is going to require a change to
implementations regardless. Using existing CSS vocabulary does
not make
... things easier.
... I'm trying to think of a scenario where importing CSS would
be easier than dealing with specific new attributes.
Nigel: The idea is for a class of processor that simply passes
the CSS properties to a CSS based implementation without
... having to process them any further, and also to put this
processor functionality behind a feature designator.
... I don't think it is especially helpful for standard
subtitle and caption presentation for example where the use
case is
... much more tied down.
Glenn: A couple of comments. One is that supporting this
feature entails having a CSS processor and integrating that
... into whatever implementation we're talking about. This
would have for example a fairly big impact on TTPE and TTV
... for example.
... The other is that in order to make use of any CSS features
from a standardisation perspective we would end up having
... to document each CSS style property that would be used in
this feature that describes how it fits into the TTML
... rendering model. We have based everything conceptually on
the XSL model but it has semantics that have in some ways
... stayed close to CSS. I can certainly see how this might
work for edge scenarios for example the one Nigel brought up
... in his proposal, like specifying a left and right border
independently of all borders, for example. But let's say you
want
... to support flex display mode via this mechanism. Now all of
a sudden you need to figure out how flex semantics
... fit into TTML formatting. It may work better in some cases
than others and will potentially have interop problems.
... Those are just the concerns that come to the top of my
thinking right now.
Andreas: I actually like Nigel's proposal, actually everything
that brings us closer to the evolution of CSS and gives us
... a more direct way of using this process in our
standardisation work. I agree we maybe need to play through a
concrete
... example and see how it works but in general I think it's a
worthwhile proposal to check.
... I think that we agreed, at least the majority of the group
agreed, to have a closer mapping to CSS in the future.
... Nobody knows how it could be done because as Glenn says
TTML is not built on CSS but on XSL-FO. It's a step in the
... right direction. After a concrete example we should
reconsider it.
Glenn: 2 more things.
... The syntactic proposal that is on the table, or something
like it, I think would be quite straightforward to support.
... The semantic one is the more problematic one. Another point
I didn't mention before is that such a mechanism would
... have to entertain the possibility of users using this
mechanism to specify properties that are already defined in
TTML
... but slightly differently, lineHeight etc. Now you have a
problem what to do. There's a lot of detail to deal with to
... effectively do this.
Nigel: The order of precedence point is already in the issue.
Pierre: If only the BBC wants to do this in their own code this
doesn't need to be in the standard.
... There's already an extension mechanism.
Nigel: That's true, my preference is to standardise but you're
right if the BBC is the only organisation with a use case here
... we can do our own thing.
Glenn: I think it's useful to continue on this to the extent
that we potentially scope out and spec out a syntactic
mechanism.
... In the end, if the WG doesn't decide to include it in some
v.next then if we've defined a reasonable syntactic mechanism
... then BBC could in fact employ that in their own namespace.
Whatever is done here I would insist on it being in a
... qualified namespace not an unqualified attribute for
example. Adding a bare class attribute would be something I
would
... oppose. I would want to see this being in some namespace
qualified attribute space.
Pierre: One additional point in response to Andreas. If the
long term goal is alignment with CSS then I'd rather spend
... effort pursuing that. Maybe the long term goal should be
for TTML to use CSS period. If that's the goal let's just go
... there.
Glenn: We do have a precedent in W3C for something similar to
this, in SVG. It has a set of XML defined properties just
... like TTML that do not depend on CSS. Then many
implementations added support for CSS stylesheets on top of
SVG.
... Most implementations support user specified stylesheets.
That's a deployed existence proof for doing something like
... this. I don't know what transitioning to pure CSS means. We
made a design decision in the beginning of this group to
... use XML syntax and not CSS syntax. Short of going back on
that underpinning principle we still have an XML syntax
... for style properties and I don't know how we could move
away from that without a non-backward-compatible revision
... of the current syntax. I fear that if we dive into that
discussion it is going to derail the immediate goal of what BBC
is
... proposing here as well.
Pierre: Glenn, my point is that BBC's proposal here has
implications on semantics that will force us to solve the
bigger
... issue. There is no perfect 1:1 mapping here. It's close,
but applying CSS semantics to TTML is going to be
... straightforward in some cases and not at all in others.
Glenn: I agree.
Pierre: This will force us to solve the deeper issue, of using
CSS period.
Andreas: In general I agree with Pierre I think. Possibly the
BBC proposal is a good opportunity to discuss this question
... and elaborate how we can use CSS more directly in TTML.
Glenn is right that over 10 years ago there was a decision
... to use XML and base styling on XSL-FO but the situation has
changed a lot since then so we need to face the new
... situation and find an answer for a future-proof model.
Nigel: Thanks everyone for the great discussion, shall we move
on from this topic?
Glenn: One last comment. I haven't looked at what SVG did to
accommodate CSS usage but it's a really important
... precedent given that it mixes XML styling with CSS, which
mirrors TTML in terms of the overlap between properties.
... Perhaps Nigel or somebody promoting this can take a look at
SVG to see if there's any guidance there.
Nigel: Good point, thank you.
f2f meeting and Joint f2f meeting with EBU Timed Text, Feb 1 2019
Glenn: A quick comment on requirements in general, I had
written in the guidelines about the requirements that
... people are encouraged to create a marked up document with
more guidance on the issue. I'd ask people raising
... requirements to try to undertake that.
Nigel: Noted, I did intend to do that.
... On the topic of the meeting, the dates and location are all
confirmed.
Andreas: We discussed this week the joint f2f meeting and had
the idea to kick off the joint meeting with some
... short presentations, on implementation work, the EBU-TT
Live Toolkit, some requirements from broadcasters about
... contribution of live subtitles to web streams. BBC, Red Bee
Media and IRT are interested in giving short presentations.
... Is this okay with the TTWG members? If yes then we can
allocate time later. I think it should not be too long, maybe
... half an hour maximum.
Nigel: Any objections to doing that? Any requests or proposals
for additional presentations?
Andreas: I think it would be interesting to hear if there are
requirements from outside Europe that are not covered, for
... example from north America. That could be interesting if
there is anyone to present it.
Glenn: I know I've mentioned it a couple of times in the past.
One thing people have kicked around in the past is some
... support for karaoke. That's a possibility. I'm not
volunteering but will try to reach out to those folk.
... We haven't logged an issue yet that records a requirement
in this area. I haven't received any concrete proposal yet
... but it is possible that one will appear before then.
Nigel: I'm hearing no objections or proposals for other
presentations so right now I believe we have consensus to go
... ahead with that idea Andreas.
[16]F2F wiki page
[16] https://www.w3.org/wiki/TimedText/F2F-jan-2019
Nigel: Thanks for raising that Andreas, if you want to go into
the wiki page and add those in, that would be great.
Andreas: Yes, I will check back with the presenters and then
add them.
Nigel: Thank you!
CSS Actions Review
Nigel: I just want to say something quickly about this.
Yesterday there was a special CSS WG meeting to discuss
... line sizing, whose minutes should be out soon if not
already. In particular I raised the question about whether ruby
... reserve is included in the line height calculation or not,
and if so, how.
... This got raised as an issue, and the initial view was that
any ruby reserve space should be added to the leading
<glenn>
[17]https://lists.w3.org/Archives/Public/www-style/2018Nov/0032
.html
[17] https://lists.w3.org/Archives/Public/www-style/2018Nov/0032.html
Nigel: to achieve the necessary effect.
... So folk interested in line sizing and ruby reserve might
want to go and take a look at that.
... The issue of background area painting did not arise because
it's orthogonal given that there's already a draft property
... for setting the background height to extend to the line
edges.
Glenn: What is that property, for the minutes?
[18]CSS line-fill property
[18] https://www.w3.org/TR/css-inline-3/#line-fill
Nigel: The "stretch" value extends the background to the line
box edges.
WebVTT
Nigel: We don't have David on the call, but let's do what we
can.
... The first thing to do (which everyone else did before I
came late to the call) is to welcome Gary who is the new Editor
... of the WebVTT spec.
Gary: There hasn't been much activity but I heard that there
needs to be work done to move the spec forward for
... Candidate Recommendation. I'm pretty new to this whole
thing. If there wasn't anyone working on it the WG would
... recharter without WebVTT but theoretically it could be
re-added the following year. For me the most important thing
... to work on is an implementation report and get it done as
soon as possible.
Thierry: As you mentioned the spec is currently in CR so the
next goal is to exit CR and move to Proposed Recommendation.
... You're probably aware of the exit criteria in the CR SoTD
section.
... We need two tests per feature so we usually demonstrate
that through an implementation report. I saw in your
... slide that Silvia sent the URL for that the report you have
is very similar to an implementation report. It would be
... good enough but from what I've seen it is just a subset of
the features.
... Therefore what the group would be looking for is a full
implementation report running the test suite against the
... four browsers. That would certainly help and having the
current status of the implementation experience.
... Also Silvia mentioned non-browsers and I would like to
understand if there are other products to use, such as VLC,
... set top boxes or polyfills.
Gary: I think VLC is probably the biggest one. JB told me at
FOMS he had implemented the spec fully. We would want
... to ratify that. If we can use VLC then that's one
implementation. Safari tech preview has most of the spec
complete
... as well and they seem to be onboard with updating things if
there are any bugs.
... Also dash.js and shaka and the vtt.js polyfill implement it
and we can update the polyfill as necessary.
Thierry: So the tests can be run on VLC?
Gary: Probably they would need to be run manually.
Thierry: OK. Just to clarify, we are not looking for a product
that implements the full spec. You could have one that does
... half, another three fourths. We are looking for each
feature to have two implementations. A full implementation
... is great but not mandatory, to clarify.
... Would you be able to provide such a report, running the
tests on the players?
Gary: Yes, the slides were just the web platform test results.
The rendering tests require manual review but the
... parsing and API test results are complete.
... I can go through that and collate a report.
Thierry: That would be great and would definitely help us to
know the status of WebVTT against implementation experience.
... If we are close to our goal of the exit criteria that would
be good news.
... Just to explain David has not much time so we are kind of
missing a Chair for WebVTT but I am ready to help. First
... let's start with this implementation report and understand
more deeply and schedule your attendance to calls as needed.
... You can attend all the calls, it's not a problem, but we're
not going to talk about WebVTT every week I guess. We can
... schedule calls with parts dedicated to WebVTT.
Nigel: +1
Pierre: Gary, thank you for joining today, it's great to see
progress there. I think we really need a Chair somehow. Gary
... that could be you. Don't quote me on it but it should not
be much work. I think we really need a Chair for this effort.
... Thierry I don't know how you want to do this.
Thierry: W3 Staff are not allowed to be Chairs. If Gary wants
to do that I can request that of course.
Gary: I would be willing to do that.
<inserted> Thierry: As Pierre said I don't think it's much
extra work except for transition but I will help
Thierry: you do that as I do with Nigel.
Nigel: I'd be happy to schedule a call Gary with you and
Thierry if you want to discuss Chairing more.
Gary: That's a good idea.
Thierry: Just one more issue is: Gary are you aware of more
comments that came in that we need to address with tweaks
... in the spec?
... For example anything substantive that would need a new CR?
Gary: I am not sure if there's anything new. There might be
something that is currently an issue against WebVTT but
... I'm not positive if changes are needed or not. I can talk
with Silvia and find out.
Thierry: Okay. The last thing is if we don't fulfil the exit
criteria, let's say there are 2-3 features not implemented,
they
... can be marked as at risk in a CR edition and removed to
allow us to get to PR. The Rec would then miss those features.
... Those are also possibilities if we don't meet 100% of
features implemented.
Gary: That's good to know.
AD Community Group
Thierry: I know that Nigel is working Chairing the AD CG. I saw
recently that it was put into the Strategy Funnel and
... therefore I'd like to understand more about how you see
this work entering the TTWG?
... Would you like it in the next Charter?
Nigel: I think I've made this point before - there's issue #4
on tt-reqs for example.
... The current status is there's a very rough draft spec for
the AD profile and there's one implementation that I'm aware
... of so far, which is the BBC's.
... The AD CG has I think 19 members currently, one more joined
today or yesterday.
... My goal is to get to a point of "good enough" spec material
to bring it into TTWG in the May 2019 Charter. Since it is
... a relatively small profile of TTML2, I am hoping we can get
to Rec very quickly.
... It's challenging but feasible I think to have the ADPT
profile at Rec by this time next year.
... Does that help?
Thierry: It sure does!
... Are there a lot of people in the AD CG who are not yet
participants of the TTWG? If that is the case would you think
... that some people would join in the TTWG and bring in new
blood?
Nigel: Yes, possibly. I would hope so, if only because from the
current active membership of TTWG I don't think there has
... been a lot of input. The one exception is the Editor is
currently John Birch who certainly was and may still be an
... Invited Expert member of TTWG.
Thierry: That triggers a last question: how do you envision the
way this spec will be specified?
... Would you like to work like we currently do with the Media
Track CG which does all the specification and editing and
... then bring it to the TTWG or would you like the CG to join
the TTWG and work within it?
Nigel: I would be open to different models but my preference is
there is one clear home for this spec work and when we
... move into TTWG then TTWG is that home. It would still be
encouraged that AD CG members provide review feedback
... and of course they can provide implementations too -
there's nothing that says implementations need to be provided
... only by WG members.
Thierry: That's a good point that it needs to be clear where
it's defined. I think it is better to have it in the TTWG if
... the current participants are okay with that and if there
are new participants who come in and help that would be great.
Meeting close
Nigel: Thank you everyone for a productive meeting as always,
and apologies again for the late start. [adjourns meeting]
Summary of Action Items
Summary of Resolutions
[End of minutes]
__________________________________________________________
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Received on Thursday, 29 November 2018 16:34:45 UTC