- From: Nigel Megitt <nigel.megitt@bbc.co.uk>
- Date: Tue, 23 Oct 2018 15:19:00 +0000
- To: "public-tt@w3.org" <public-tt@w3.org>
- Message-ID: <D7F5087C.6B7FD%nigel.megitt@bbc.co.uk>
All, thank you for attending the face to face meeting at TPAC 2018 in Lyon, and thank you also to the observers. Minutes are listed on our wiki page at https://www.w3.org/wiki/TimedText#TTWG_Working_Group_F2F_meetings
Direct links:
Day 1: https://www.w3.org/2018/10/22-tt-minutes.html
Day 2: https://www.w3.org/2018/10/23-tt-minutes.html
Kind regards,
Nigel
In text format:
Day 1:
[1]W3C
[1] http://www.w3.org/
Timed Text Working Group Teleconference
22 Oct 2018
See also: [2]IRC log
[2] https://www.w3.org/2018/10/22-tt-irc
Attendees
Present
Glenn, Nigel, Andreas, David_Singer, Pierre
Regrets
Chair
Nigel
Scribe
nigel
Contents
* [3]Topics
1. [4]Agenda bash
2. [5]M&E IG joint meeting preparation
3. [6]TTML Profile Registry issues
4. [7]Break, then Media and Entertainment IG.
* [8]Summary of Action Items
* [9]Summary of Resolutions
__________________________________________________________
<scribe> scribe: nigel
Agenda bash
Nigel: Looking at our agenda:
[10]TTWG TPAC Agenda page
[10] https://www.w3.org/wiki/TimedText/tpac2018
Nigel: I don't think we will have a joint meeting with CSS WG
Andreas: Tomorrow I'd like to discuss closer alignment with CSS
Glenn: I'd like to consider TTML2 2nd Ed requirements
Nigel: We have an agenda topic for that tomorrow - I have a use
case to bring also.
Andreas: For the agenda, I don't think we need anything for
TTML <--> WebVTT mapping.
Nigel: Yes, we took that off the agenda already.
... Glenn asked to discuss Karaoke.
Glenn: I don't have anything prepared for that, so we can
scratch that off the agenda
... or cover it very quickly.
Andreas: There will be topics relative to the TTWG that will
come up during the M&E IG,
... like 360º VR and AR.
... I have to be at the AC tomorrow from 3 so I will not be
able to join the future requirements
... session.
... Can we move the future requirements to after lunch and then
audio profiles later?
Nigel: OK
Andreas: I need to go to the M&E IG now, see you there later!
<glenn> Note: github.com is undergoing technical problems, see
[11]https://status.github.com/messages
[11] https://status.github.com/messages
Nigel: I will start to prepare some slides for our joint
meeting with M&E IG now.
Glenn: I think we need to cover WebVTT and the status
Pierre: We should discuss the TTML ballots also
... If it helps we could walk people through the
implementations
Nigel: When should we cover WebVTT?
David: My feeling now is that we won't get enough input to get
to PR and Rec so we
... should leave it there and propose that we drop the work and
publish as a WG Note.
... If nobody comes forward to say "I'm willing to do the work"
then we should go with
... that proposal.
Nigel: Do we need an agenda topic to take that any further?
David: I will check if anyone else from Apple is likely to
attend today or tomorrow.
Nigel: The main body of our meeting is tomorrow - I have
prepared some material for
... the discussion on live subtitle topic.
Pierre: If the group decides to tackle this, the first step
should be for the WG to accept
... the system model, as the basis for the work.
Nigel: +1
Pierre: I think there's real confusion about the production
process vs the "broadcast encoder"
... for want of a better term. Once it hits ISOBMFF, what
happens, for example? Does
... anything special have to happen after the emission encoder
or is it really upstream.
... Even if we could publish a Note and tell people to look for
it before asking questions
... that would be helpful.
Nigel: I feel I will be able to answer that question!
David: On the WebVTT proposal, I will take an action to send a
note to the mailing list
... explaining the proposal. If we get no response we should
take silence as assent.
M&E IG joint meeting preparation
Nigel: [bashes presentation deck for joint M&E IG]
Pierre: For future requirements for TTML, it would be useful to
think about the language
... in the core about style attributes, and allowing for
additional modules.
Glenn: If we have modules that try to apply diffs to the core,
that becomes messy.
Pierre: Maybe we would choose not to support that, but to
support plugins for example
<scribe> .. new style attributes that participate in the style
resolution algorithm.
Glenn: I don't know if anyone wants to discuss 3D and adding a
z-value dimension to
... text positioning.
... I'm having a conversation about future requirements
concerning a DOM API
... for TTML, from an organisation interested in translation
and localisation.
... It would be to support Javascript processing of TTML for
example.
... Perhaps that's the conceptual model that the organisation
I'm talking to has in mind.
Nigel: I've uploaded that to
[12]https://www.w3.org/2011/webtv/wiki/Face-to-face_meeting_dur
ing_TPAC_2018#14:45_-_15:30_Timed_Text_Working_Group_joint_meet
ing
[12] https://www.w3.org/2011/webtv/wiki/Face-to-face_meeting_during_TPAC_2018#14:45_-_15:30_Timed_Text_Working_Group_joint_meeting
TTML Profile Registry issues
Nigel: Given that GitHub is down, this may not work too well...
... I can see we have some new issues.
Glenn: Nigel had a question about #52
... It's a portmanteau issue where the details will be in the
Pull Request
Nigel: Please don't do that - you're asserting there's
something wrong with the text
... and planning to go ahead with a pull request before getting
any discussion that
... concurs with your review. Be prepared to get push back from
the WG on that.
Pierre: But what is wrong with the text?
Glenn: For example Respec complains about a normative reference
in a non-normative section.
... Another is inconsistent capitalisation.
Pierre: OK, editorial things.
Glenn: I'll throw them in the summary to help with review.
Pierre: Are there any non-editorial issues?
Glenn: If there are then I will open a separate issue for them.
... There's also some language in the prologue to the media
registration part that talks
... about plans for sending to IANA but we have already done
that so it no longer applies.
... It can either be removed or truncated.
... The biggest change I'm going to propose is changing §4.2 to
informative. I'm not sure
... how it got in there, I wasn't paying attention apparently.
It's quite problematic.
... It purports to describe how to resolve the profile of a
document.
Pierre: That was before TTML2
... We should just fix it.
Glenn: I'm willing to keep it in as an informative section.
Nigel: It precedes TTML2 and the referenced specifications
describe their own ways of
... identifying the document instance's profile. In that sense
it is informative because it's
... a gathering of other information.
Pierre: One possibility is to remove §4.2 - that would be my
preference.
Glenn: That would be my preference too.
Pierre: This is trying to be helpful, I understand.
David: It seems like a good answer to help people derive what
profile a TTML document instance is.
... It should be informative.
Glenn: The trouble is that it is not what TTML1 or TTML2 says.
David: It shouldn't be wrong!
Pierre: Right, it is possible to summarise, and should not be
too much trouble, to say
... where to look at in a TTML document instance to find what
kind of thing it is.
Glenn: I don't even mind suggesting one possibility of using
XPath. Maintaining this
... data is not part of the registry.
Pierre: And its wrong!
Nigel: Is it?
Pierre: Yes, especially in TTML2 you have precedence rules
about content profile, profile
... attribute...
Glenn: profile override, outer context...
Pierre: yeah
Glenn: For example for tt1t it doesn't refer to what TTML1 or
TTML2 does.
Nigel: The XPath thing doesn't say you must use XPath.
Pierre: IMSC does not use this technique for deciding if a
document is IMSC compatible for instance.
Glenn: I don't know of any implementation that uses this
technique.
Pierre: I would replace it with a more descriptive prose
section.
David: It is useful to help find what kind of TTML document
instance you have in front of you.
... What the document claims to be.
Pierre: You can validate any document against any profile to
see if it valid.
David: You need to know what a document claims conformance to.
Glenn: You're conflating content profile vs processor profile.
Nigel: I didn't hear that from David.
David: It seems like a reasonable question to ask what a
document claims conformance to.
Glenn: It's out of place in the registry because the codecs
profile does not refer to content profiles.
Nigel: That's true.
... I would maybe rewrite it and put it in an appendix rather
than have it in §4.2.
David: The codecs parameter is useful and you need to know how
to specify it based on a document
Nigel: Subtle distinction: it's about knowledge of the
document, not the document itself.
... It may be that you know a doc is EBU-TT-D and IMSC but the
document doesn't make
... any claim internally. You can set codecs based on that.
Glenn: You also may know you don't need full processor support
for every feature.
... By the way the document doesn't set a precedence order for
profile vs codecs
David: Why is it called codecs?
Pierre: So it can be used in MP4
David: You can copy the codecs value across?
Pierre: Yes
<glenn> github outage incident report:
[13]https://blog.github.com/2018-10-21-october21-incident-repor
t/
[13] https://blog.github.com/2018-10-21-october21-incident-report/
Nigel: This is what goes after stpp.
David: It's the sub-parameter for the codecs? Got it.
Glenn: My action is I plan to make a PR for this based on the
input I've heard today.
... Instead of removing it entirely I'll take the approach that
Pierre suggests, to try to
... summarise it, and add a statement that it's a non-normative
section.
Nigel: I would consider moving it to an appendix too.
Glenn: That would be my preference too. I may leave behind a
pointer.
Nigel: I don't think that's needed.
... It would be useful to merge #43 before you do a pull for
#53 Glenn
Glenn: I agree, please can we merge them soon?
Nigel: Any objections to merging the open pull requests?
Glenn: We will probably end up tweaking the result of that to
deal with other issues.
Nigel: I'm not hearing any objections.
... Please note Mike is the editor here and wants to continue
with that.
Pierre: Just create a pull request and Mike can be in charge of
merging it.
Nigel: Will you do the pull to add TTML2 profiles Glenn?
Glenn: Yes, and for #38 (Content Profiles vs Processor
Profiles) too.
Nigel: That's all on this topic. I propose we take a break and
then join the M&E IG for
... the rest of the day.
Glenn: I'm going to join that later.
Nigel: Okay!
Break, then Media and Entertainment IG.
Summary of Action Items
Summary of Resolutions
[End of minutes]
__________________________________________________________
Minutes manually created (not a transcript), formatted by
David Booth's [14]scribe.perl version 1.154 ([15]CVS log)
$Date: 2018/10/22 14:29:40 $
[14] http://dev.w3.org/cvsweb/~checkout~/2002/scribe/scribedoc.htm
[15] http://dev.w3.org/cvsweb/2002/scribe/
Day 2:
[1]W3C
[1] http://www.w3.org/
Timed Text Working Group Teleconference
23 Oct 2018
See also: [2]IRC log
[2] https://www.w3.org/2018/10/23-tt-irc
Attendees
Present
Glenn, Nigel, Andreas, Pierre, Vlad, Vladimir, Peter,
Philippe, Yam_ACCESS
Regrets
Chair
Nigel
Scribe
nigel
Contents
* [3]Topics
1. [4]Agenda for today
2. [5]Live Subtitle and Caption contribution
3. [6]Live subtitle contribution - discussion
4. [7]AC Review feedback
5. [8]TTML1 3rd Edition Rec CfC
6. [9]Future Requirements
7. [10]New requirements: 360º/AR/VR
8. [11]TTML Documents Container
9. [12]Additional styling
10. [13]Audio Profiles
11. [14]Meeting close
* [15]Summary of Action Items
* [16]Summary of Resolutions
__________________________________________________________
<scribe> scribe: nigel
Agenda for today
Nigel: Good morning everyone, let's do introductions.
... Nigel Megitt, BBC, Chair
Andreas: Andreas Tai, IRT
Glenn: Glenn Adams, Skynav, been working on TTML since 2003!
Nigel: Thank you, and observers.
Masaya: Masaya Ikeo, NHK - Yam_ACCESS
Geun: Geun Hyung Kim, HTML5 Converged Technology Forum (Korea)
Nigel: Today, we have Live subtitles and caption contribution,
AC review feedback,
... future requirements, and Audio profiles.
... Welcome, we have another observer:
Hiroshi: Hiroshi Fujisawa, NHK
Toshihiko: Toshihiko Yamakami, Access Co., Ltd
Andreas: For the future requirements topic, after lunch, a
colleague may want to join on
... the requirements for 360º subtitles and possibly other TPAC
attendees may want to
... join so if we can figure out a specific slot that would be
great.
Nigel: If there are timing preferences we can be flexible -
probably any time after 11:30 we can do.
Andreas: Thanks, I'll get back to the group on that.
Live Subtitle and Caption contribution
Nigel: I uploaded a short presentation:
[17]Presentation on live subtitles and captions
[17] https://www.w3.org/wiki/images/f/f4/Live_subtitles_presentation_BBC_TPAC_2018.pdf
Pierre: Pierre Lemieux, Movielabs, Editor IMSC
Nigel: [presents slides]
Pierre: Question about the client device being unaware of live
vs prepared source, and
... the system being designed with that as a constraint.
Nigel: Yes, assume that is the case.
Glenn: The distribution packager might assign DTS or PTS?
Nigel: Yes, I should have added MPEG2 Transport Streams as a
possible output, and we
... should note that there is a DVB specification for insertion
of TTML into MP2 TS.
... [slide on transport protocols] If there is timing
information from the carriage
... mechanism then that might need to be understood in relation
to processing any
... subtitle TTML document.
Glenn: Are you hoping an RTP packet will fit within a single
UDP packet?
Nigel: In general that is likely to be true, but not
necessarily.
Pierre: So you can't rely on the network providing you with
ordered documents?
Nigel: Yes, that could be the case.
Pierre: So the protocol you use has to be able to handle
non-sequential document transmission?
Nigel: Yes, potentially.
... You do need to resolve the presentation in the end, and
some deployments may
... provide fixes for out of order delivery at the protocol
level (WebSocket) or at the
... application level and we need to deal with the whole range
of possible operational conditions.
group: Discussion of options for defining the begin and end
time of a TTML document.
Nigel: [proposal slide]
Glenn: I wouldn't object to using the ebu namespace as long we
don't normatively
... reference the EBU spec. I'm not willing to cross the
rubicon when it comes to bringing
... in non-W3C namespaces into TTML.
... If it is published as a Rec track document and it refers to
TTML and is a module that
... blesses these features, using EBU namespace to define them,
then that's okay with me.
... If we have an assumption that we are going to pull that
into TTML directly then I might
... start having some discomfort.
Andreas: I think we are not there yet at this point in the
discussion. First we have a problem
... that we are trying to solve and we have a standard that is
already out there. It is good
... practice not to duplicate. What Nigel has proposed
addresses a good part of this
... scenario, and there has been a lot of discussion since 2012
on this with at least 3 years
... regular active work on it, so I think it is worth looking
at it. After reviewing this and
... deciding that this is how we want to solve it then we can
look at how to adopt it.
Glenn: Right, I just wanted to give fair warning about the
questions I might have.
... A question I have is why we need to do something in W3C?
... Is it a profile of EBU-TT?
Andreas: Good question. It is limited to certain vocabulary and
mainly has the constraints
... from EBU-TT, which are not the same as for IMSC. It would
be perfect to use the same
... mechanism for all IMSC documents.
Nigel: That was my answer, it makes sense to bring these key
semantics into the home
... of TTML so that it can be applied to other profiles than
EBU-TT.
Glenn: Is it an authoring guideline?
Nigel: Why would it be a guideline?
Glenn: It's not defining new technical features.
Nigel: It is indeed doing that.
Pierre: There might be technical features such as defining
document times as mentioned.
... A lot of the guidelines could be in the model, but I
suspect there would be some
... requirements and substantive features.
Nigel: [propose a break for 30 minutes]
Live subtitle contribution - discussion
Pierre: Is the proposal for an EBU Member Submission?
Nigel: It could be but I think it is not needed - the IPR can
be contributed by EBU as
... a member based on any work that we do in this group.
Andreas: There is a question for a member submission if it will
be superseded by a future
... W3C specification. The market condition is that people are
pushing for implementation
... of EBU-TT Live so we should be clear about what we want to
do in W3C.
Pierre: This sounds more like an EBU discussion, W3C cannot
require implementation.
Andreas: It could affect adoption though since work on an
alternative may change views.
Pierre: That's an EBU decision. Anything could happen when a
member submission arrives here.
Andreas: We can review the document as it is and then review
what is needed. I don't see
... a need for a member submission at the moment. What
advantage do you see in EBU submitting one?
... The spec is out there, everyone can use it, IPR issues
should not be a problem.
Pierre: I can't speak for EBU but I would think that a member
submission clarifies
... significantly the scope of the effort, being live subtitles
within the member submission
... scope rather than live subtitles in general.
... IMSC ended up different from CFF-TT for good reason, but
the scope of the features
... for instance was set by the member submission. It would
help.
Andreas: The different arguments that led other W3C members to
make submission is more
... internal, how to move on with some standardisation. In the
past submissions are
... submitted to W3C, then carefully reviewed, when W3C should
take over certain
... standardisation.
Pierre: For instance, CFF-TT - the Ultraviolet members and the
larger community felt that
... it would be beneficial if something like that specification
were to be standardised by an
... organisation like W3C. That was a decision by that
community to do that. But it was not
... happenstance. Here, I think it is up to EBU and its members
and community to have an
... opinion on whether or not standardisation by W3C helps or
not.
... It might not help if it changes the specification in a way
that is not good for that
... community. You tell me.
Andreas: We are not there yet. This group has not decided yet.
Pierre: Live is really important.
Andreas: Yes, this is something we need to discuss. What is in
scope for this group?
Pierre: The industry is interested in live, period.
... It is a really important use case.
Nigel: [repeats goal from earlier]
Pierre: If the goal is to arrive at how to create a set of IMSC
documents in a live environment...
Andreas: What Nigel said, and other EBU members, is there is
support to make EBU-TT Live
... a subset similar to how EBU-TT-D is a subset of IMSC Text
Profile.
Pierre: That works.
... You don't need a member submission for that. Deciding on
the scope early is a good idea.
Andreas: Yes
Pierre: Both make sense. Picking one is going to be really key.
Nigel: I think I hear consensus that some kind of TTWG
technical report that addresses
... the live contribution use case is worthwhile.
Glenn: Requirements would be useful to set the scope.
Pierre: Yes, a requirements document would be helpful.
Glenn: In general we should have requirements documents before
new technical specifications.
... I make a motion to require that.
Andreas: I propose a joint meeting with EBU group to discuss
this. We have January in Munich
... in mind. We wanted to bring this up and see what the
availability of members.
Pierre: Feb 1 in Geneva would work for me.
Andreas: That is good.
Pierre: Specifically the morning of Feb 1!
Andreas: Propose 31st and 1st.
Pierre: I'm busy Friday 1st in the afternoon but the joint
meeting could be just in the morning.
... We don't need more than 3 hours.
Glenn: If we're having a face to face meeting it should be at
least 2 days, if it is an official
... WG face to face meeting.
Pierre: I think we are just proposing a joint TTWG - EBU
meeting.
Glenn: That would make it a TTWG f2f, I can't justify a journey
to Geneva for half a day.
Andreas: If we make a one and a half day meeting, on Thursday
and Friday.
Glenn: I'm available on Saturday too.
Pierre: I'd rather not, my preference would be 30th and 31st
and part of the 1st.
Andreas: It would be good anyway to have the EBU and TTWG
members in a room together.
Pierre: We can do it during PTS, why not?
Andreas: We need to ask Frans and EBU.
... I will ask Frans.
Nigel: Thanks, summarising the discussion:
... * A technical report on live subtitle contribution is a
good idea
... * We need requirements for that
... * We will investigate a joint meeting with EBU at end of
Jan/beginning of Feb
... Thank you.
Pierre: Thanks for bringing this up.
... At some point we will have a technical discussion about the
details, based on the
... requirements, which will be crafted hopefully prior to that
meeting, and that would be
... a good time to have a technical discussion.
Glenn: Does the current Charter cover this work?
Nigel: The requirements document would be a Note so that would
certainly be covered.
... We don't have a specific deliverable for a Recommendation
listed at present, so that
... may be something that we should consider for a Charter
revision.
... By the way, if we proceed with David Singer's proposal from
yesterday, that could be a
... good moment to revise the Charter in any case, since the
WebVTT Rec deliverable would
... have to be pulled from the Scope.
... For example we could target a Charter revision in May 2019
for another 2 years, pulling
... the end date to 2021.
Glenn: 2023 will be the 20th anniversary of this WG.
Andreas: Noting that there are observers here who might be
interested in this topic, if we
... proceed with this work we should make it possible for new
members to join our meetings.
Nigel: As Chair, I would like to know if there are any
potential members especially in
... different time zones and to be flexible about how we meet
to allow them to participate.
Andreas: I also meant that it should be possible for
non-members of TTWG to participate
... in the discussion.
Nigel: For a non-Rec track requirements document with no IPR,
that is fine of course.
... To clear IPR rules when we get to a Rec track document
obviously contributors do need
... to be WG members, effectively.
Glenn: If we publish a Rec track document that is based in
large part on another spec
... outside of W3C then that may be precedent-setting.
Pierre: Like IMSC?
Nigel: It's not precedent setting.
Pierre: It's the same, it's based on TTML.
Nigel: I agree.
Pierre: From what I have read it's a how-to-interpret TTML
document crafted in a particular way.
Glenn: That's reasonable.
AC Review feedback
Nigel: Reviews AC feedback. We don't have any comments to
respond to.
... We have a reasonable number of responses now, some more
would be good.
TTML1 3rd Edition Rec CfC
Nigel: I realised that in my CfC for publishing the TTML1 3rd
Ed Recommendation, I did not
... include any consideration of superseding 2nd Edition. I
don't think we need to do that
... for TTML2 or IMSC 1.1, because the previous Recs still
stand, i.e. TTML1 3rd Ed and IMSC 1.0.1.
... Can I make it a condition of the CfC that we supersede
TTML1 2nd Ed when we
... publish TTML1 3rd Ed.
Glenn: It would be inconsistent not to.
Pierre: Yes, supersede not obsolete.
... In the fullness of time we should probably make an Edited
Recommendation of
... IMSC 1.0.1 to point to TTML1 3rd Edition too.
Andreas: Yes, superseding is okay.
Nigel: Thank you, that's a decision.
RESOLUTION: As part of the request to publish TTML1 3rd Ed as a
Recommendation we will supersede TTML1 2nd Ed.
Nigel: We'll break for lunch now, back at 1300.
Future Requirements
Nigel: Since the break, we have a new observer and a new
attendee:
Vladimir: Vladimir Levantovsky, Monotype, AC Rep, Chair of Web
Fonts WG (awaiting re-charter)
... I have a very keen interest in anything relating to text
matters, including composition,
... rendering, fonts and anything else you can imagine related
to that.
mdjp: Matt Paradis, BBC, Chair of the Web Audio WG, and I run
an accessibility and interactive
... work stream for BBC R&D, which is where my interest in this
group lies.
Peter: I'm Peter tho Pesch, from IRT. I'm working on a project
to do with accessibility of
... 360 and AR environments, particularly subtitles.
Nigel: Thank you, welcome.
... Can I first get a very quick list of the new requirements
areas that we want to cover in
... this conversation?
... I already have 360º/AR/VR requirements.
... This morning we covered live subtitle use cases so we don't
need to duplicate that work.
... I need to present some styling attributes for
consideration, actually a bigger question
... about bringing in arbitrary CSS and how we might go about
doing that.
Andreas: I recently came across a requirement for a TTML
documents container element.
New requirements: 360º/AR/VR
Andreas: Just to start on this, yesterday we had at the Media
and Entertainment IG a
... brief session where I showed some of the results of the
work Peter has been doing.
... We did not get into the detail, I just showed the videos
and we agreed there is a use
... case that needs to be solved, and there is not complete
agreement, or it is not clear yet
... where it should be solved. The M&E IG action was to
organise a telco where we get the
... necessary people from different groups together, discuss
the problem scenario and then
... work out where the work will be done.
... Yesterday, because I walked through the different examples,
I would like to repeat this
... with Peter's comments because he has the necessary input.
... Because Vladimir is working on a similar topic and
yesterday brought up some additional
... issues we may want to make a list of all the things that
could be in scope of the TTWG.
Nigel: Just to note, our Charter includes in the Scope:
"Investigate caption format requirements for 360 Degree, AR and
VR video content."
Vladimir: And "caption" doesn't necessarily mean subtitles, it
could be any text label that
... is part of the content?
Glenn: We don't distinguish between subtitle and caption any
more!
Vladimir: Would text label be considered in scope?
Glenn: Why not?
Andreas: The group name is Timed Text, which is very generic
and doesn't say what it is
... used for. For general matters also there is the CSS group.
Vladimir: I understand we will not cover all the presentation
cases.
... For example when you're in a 360º environment the text will
be defined by timed text,
... but the composition might be defined by CSS.
Nigel: Consider this in scope.
Andreas: [shows examples]
Peter: I will start here at this slide. Yesterday you showed
already a little bit of the scope.
... I often use this image because for me it was the easiest
way to picture the coordinate system
... we are using.
... [world map, equirectangular projection]
... You also know how this would map onto a sphere. This is a
common way to represent
... 360º videos, using this map and wrapping it round a sphere,
putting the viewer at the
... centre looking out (the other way from the way you see a
globe normally).
... Within the project I am working on, we are looking into
ways of adding accessibility
... services to VR, focusing on 360º videos right now.
... There are some challenges, maybe we start with the videos
to show you some of the
... thoughts we had on this.
... [always visible] This is the simplest mode, where the
subtitles are always shown in the
... viewport where the viewer is looking.
... This is a basic implementation, you can see the subtitle
text always sticks in one position.
... In this example the text is aligned to the viewport not to
the video.
... [example with arrow pointing at the speaker]
... Here if the speaker is off screen an arrow points to the
left or right to show where the
... speaker is located. It disappears when the speaker is in
the field of view.
... It's a small help for people to find where the action is.
... The basic presentation mode is the same.
... [fixed positioned] This is a completely different approach.
... The subtitle is now fixed to the video not the viewport,
like a burned in subtitle. The way
... it is shown here, I don't know where this is used in
practice, but there is an example
... where the subtitle text is burned into the video at three
different positions and fixed there.
... [Formats]
... A quick overview of how we implemented this.
... IMSC, DASH, h.264 video.
... Custom extensions to IMSC for providing the information we
needed.
... In this example, imac:equirectangularLong and
imac:equirectangularlat are specified on the p element.
... They specify a direction in the coordinate system, not
really a position. You could specify
... a vector and where the vector hits the sphere, that is
where the subtitle is located.
... This is used for the different implementations.
... This is the current status.
... Future thoughts: subtitles with two lines in each subtitle,
belonging to different speakers
... at different positions, so different angles for each
speaker. We could add the attributes
... at the span level but we did not do that yet.
... Also what information the author can add to indicate the
suitable rendering style.
Andreas: That's better than what I said yesterday! And it
doesn't contradict it.
... Yesterday there was the generic question where should this
gap be addressed.
... It was clear that TTWG comes into this. I think it's
worthwhile first discussing if this kind
... of use case falls in scope, and if these two attributes
would be something that could
... be added to TTML and IMSC, and what additional features are
needed.
<glenn> +q
Glenn: Those are very long property names, and they embed a
particular projection semantic.
... If they were to be put into TTML I would probably prefer
shorter names as well as
... extracting the projection method to a separate parameter
for the document level.
... As far as potential requirements, I think this is good and
we should consider doing something in a standard.
... We would have to define in the spec the transformation from
the spherical coordinate
... space to the projection coordinate space, for different
projections, e.g. a projection method parameter.
<Zakim> nigel, you wanted to ask about distance and to ask
about other presentation models and to ask about doing the
projection based on a rectangular region
Nigel: Why not use a 2d coordinate like for the video image and
then project the text in
... the same way as the video, rather than including the
coordinates?
Peter: We thought about that. We have an additional mapping
step. One way would be to
... base the IMSC file on the 2D texture and then use the
mapping mechanism that is
... defined by the standard for mapping the video, also for the
subtitle file, or to define
... information directly in the IMSC in the target coordinate
system.
... We used this approach here because it is a lot easier to
implement. This is the
... rendering coordinate system and it is easy to map the video
texture on a sphere in the
... framework we are using. Then it is a lot easier to define
the coordinates directly.
Glenn: Right now the x and y coordinate space in TTML is
cartesian based and we have a
... great deal of semantics, for example the extent of a
region, is defined in x and y
... coordinate space. You could use a reverse transformation as
long as you have the
... central meridian and standard parallels for doing a reverse
projection to the
... equirectangular form. I think we should be hesitant to
express coordinates in a
... coordinate space that is not based on our assumed cartesian
space. I would rather do
... a reverse transformation, specify x and y and map to
spherical coordinate space.
Vladimir: A question. Everything so far seems to be related to
flat 2D projections. How would
... that apply to a stereoscopic environment.
Nigel: That was one of my questions - how do you specify depth?
Vladimir: You can break the user perception by getting it
wrong.
Nigel: We have disparity already but I don't know how disparity
fits with the 3d coordinate system.
Peter: We also looked at MPEG OMAF (omnidirectional media
application format) and the
... draft describes how to add subtitles to the 3d space, and
it supports WebVTT and IMSC
... subtitles, and the IMSC subtitles are added in a way where
the MPEG scope provides a
... rendering plane for the IMSC to be rendered onto. The
information in the IMSC document
... is included in the OMAF format. There's an additional
metadata track that contains those
... information and that handles the information in the way
MPEG does it. There is a box,
... for regions, and for points in their coordinate system. You
basically get a rectangular
... plane for rendering your subtitles onto.
... It also includes depth information for stereoscopic
content.
Nigel: If there's depth information in the video then there
must be depth in the subtitles,
... how do those two get aligned?
Peter: I didn't fully look into this, but the standard suggests
a default depth and radius
... for the video sphere, and according to this you can either
add depth information relating
... to radius or directly add disparity information. The
disparity information is not connected
... to the video because it is connected to the presentation of
the stereoscopic image, and
... you would need to provide a left eye and right eye video
stream.
Andreas: I want to point to Vladimir and ask: yesterday you
brought up some additional
... things. Apart from positioning, what other things may be
useful or needed?
Vladimir: Yesterday I mentioned, speculatively, without a
specific application in mind,
... text objects need some kind of perspective transform to be
applied.
... How much detail we go into depends on how the
responsibilities of text transform are
... split between different parts.
Andreas: I wondered if CSS WG are working on the same thing, or
another WG.
... I think positioning of arbitrary HTML or whatever in this
space could be in the long
... run in the requirements. I don't want to contradict here
what is being done in other groups.
Vladimir: I haven't heard anything about CSS considering 3D
layout issues.
Philippe: The Immersive Web WG was created last month.
Andreas: I spoke with Chris Wilson yesterday.
Philiipe: He's one of the Chairs.
Andreas: I asked if we could present this use case tomorrow, he
thinks it's not the right
... moment, and prefers that it gets discussed in the WebXR CG,
which has a repository
... for requirements. If we open a requirement then we should
open it there.
Philippe: We should ask the APA WG which is a coordination
group for accessibility too,
... you should ask Janina. She might well say it came up on
their radar. I don't think they
... have done any work on it.
Andreas: In this project we are also discussing user interfaces
and this is definitely an
... issue for the APA WG, UIs for navigation and control of
access services.
Philippe: It's not just UI!
Andreas: OK.
Philippe: We don't have an accessibility group for the 3d space
right now but that is where
... the discussion should begin.
Vladimir: The Virtual Reality Industry Forum is another one
outside W3C. We are still in the
... exploration stage. We know what needs to happen to do what
needs to be done in the
... web, for example what to do with web fonts.
... [i.e. web fonts might need some work]
Andreas: That group could point to something in W3C?
Vladimir: Yes, it would be a huge help to point to something
from W3C.
Peter: There's one thought I wanted to add. When we look at the
scope of MPEG OMAF,
... keep in mind it is a distribution format, and it specifies
how to bring the content to the
... consumer but when you look at the complete chain the
content will probably not be
... described in OMAF. The subtitle workflow - it makes sense
all the subtitle information is
... kept in one place. You can look at it in two ways - either
the positional description being
... like a styling attribute or a kind of metadata to transport
the information to the MPEG
... format to distribute it to the user. Maybe there are two
different use cases. One to
... describe subtitles in a 3D space, something like an
extended IMSC, or you could say
... we need additional metadata, just tunnel this information
to the point where the complete
... format is mapped to a 3D space.
Nigel: Question: Do you need to describe the speaker position,
the text position, or both?
Peter: That's a very good question. At the moment we are just
pointing at the centre of the
... speaker with no height information. We don't differentiate
the speaker position or the
... text position. They might be different.
Nigel: A follow-on question: what user information do have
about preferences? Which of
... these do people want to use, one in particular or different
people prefer different ones?
Peter: It's too early to say, research is ongoing. There are
different results from different
... tests pointing in different directions. For example a
university in Munich found that half
... of the test users preferred fixed position, and half didn't
like it. It has the advantage
... that it is more comfortable to view and induces less
sickness but you can miss the
... subtitle if you are not looking the right way. We are still
looking to find the best way.
Andreas: How does VR-IF Forum relate to MPEG OMAF?
Vladimir: I think they have a liaison or they are just the same
members. I doubt there is a
... direct official relationship between the two.
... VR-IF doesn't specify anything but produces usage
guidelines. It's a different level, not
... technical specifications.
Andreas: The other question is regarding font technology.
Recently I have seen a lot of
... advancement of the use of variable fonts on the web, with
one font file with a large number
... of font faces you could use. From the discussion I've heard
this 3D space presents a
... different kind of graphical challenge, and I see good
application of variable fonts in this
... space which I think should be explored.
Vladimir: I absolutely agree.
... The reality is when you rely on a particular font feature
to be available it would be
... too optimistic to rely on the font that happens to be
resident on the user's device.
... When you rely on a specific font feature you're best/only
bet is to serve the font to the
... user so you know the font is present.
... Same with variable fonts, which are in the early stages of
deployment. If you want to use
... them then you need to provide the font.
... In VR-IF nothing is taken for granted, and if a particular
font is needed, for feature or
... language support, then that font has to be provided. On the
web the font can be downloaded,
... in ISOBMFF there is a way to provide a font.
Glenn: TTML2 supports font embedding now either directly in the
TTML document or by
... URL reference to the environment somewhere which in the
context of ISOBMFF could be
... part of the font carousel that's available.
Andreas: Is this in IMSC 1.1?
Nigel: I don't think so.
... [confirms this by looking at the spec]
Andreas: TTML2 has a wide feature, IMSC is a subset that
doesn't support this. At the
... bottom line there should at least be a mechanism for the
content provider to provide
... the font.
Vladimir: Absolutely. If you expect that variable fonts are
useful in this environment then
... you have to provide them.
Andreas: As a proposal for the next steps, would it be a
strategy to first try to fix the
... requirements and describe the use cases we are trying to
solve?
... If this is ready then we can schedule the Web Media &
Entertainment call on the IG and
... discuss it.
Nigel: Sounds good. Are there other members than IRT interested
in this?
Vladimir: I am interested, I am learning more than I can
contribute.
Masaya: Can TTML associate a piece of timed text with a point
in space where the sound originated from?
Nigel: I think there is no standard way to do that now, no.
Vladimir: You're suggesting two independent spatial references,
one for a specific location
... and the other for a location of the source so if we wanted
to implement the arrows
... solution we would know the location of the source?
Masaya: yes, I'm just curious.
Nigel: I think that is for the requirements document to
describe.
... Matt, do we have data for object based media pointing to
where sound should be positioned in space?
Matt: We do have prototype metadata for azimuth, elevation and
distance, but there's a long
... step between that prototype form and something that could
be broadcast.
Nigel: Does it inform the data modelling?
Matt: It does, elsewhere we look at graph data for object based
productions, and this is
... at a higher layer than something like the Audio Definition
Model.
... It gives a reference for speaker or events or "sounding
objects".
Nigel: I would suggest we should use the same coordinate system
for things we can see
... and things we can hear. It could be an accessibility issue,
to allow transformation between
... visual and auditory information.
Matt: It's a fundamental to get the coordinate system right.
For example in Web Audio WG
... we had to decide whether azimuth goes clockwise or
anti-clockwise. Standardising on
... a common API is important.
Andreas: For gathering requirements, typically we would start
to describe what we want
... to solve, and then all these questions will come up. We
also learned from this discussion
... that a lot of things come to mind based on what has already
been specified, which will
... come up when the requirements are clear and we are moving
to a solution.
... Peter you said you are willing to put some work into the
requirements?
Peter: Yes definitely.
Andreas: Vladimir also said you are interested. I can be
involved but I'm not an expert in this.
... I can be a link and help out.
... That would be my proposed action that you two and anyone
else who is interested tries
... to work out these use cases, and directly post it on the
GitHub repository.
Nigel: What GitHub repo?
Andreas: The XR CG has a repo for requirements or proposals,
that was Chris Wilson's
... proposal and it's a good start to get it out there for
everyone to access.
Peter: OK, for my understanding what we provide first is the
use cases and what we want
... to do, and the question is does it involve links to
existing standards?
... What standards are there to help solve these issues?
... What is within the scope of the TTML WG?
... Or the other WGs.
Vladimir: At this point we should probably have a critical eye
on the existing standards.
... If the standard exists it doesn't mean it was complete,
correct or designed with the same
... use cases in mind. The existing standards may need to be
amended to be useful.
... There may be something missing, which is useful information
for the folks who
... developed those standards. For example just because OMAF
exists, doesn't mean it is
... capable of supporting all possible use cases. If we find
one that is not supported they
... would welcome the contribution.
Peter: +1
Andreas: What you say makes a lot of sense Vladimir. I would
propose to systematically
... separate this so first we have a green field of what the
use case is to solve, and the
... requirements, and open up the issue on GitHub, then
immediately afterwards reply to
... it and say "these standards address this already" and then
the discussion starts.
Peter: Yes
Vladimir: I have to leave now, thank you.
Peter: I will leave too, thank you.
Philippe: [went some time ago]
Nigel: Thank you all.
TTML Documents Container
Andreas: Recently a European broadcaster asked me if TTML can
have multiple tracks,
... for example different languages per file.
... I said no that's not how it is defined, you have one
document per track.
... For authoring and archiving they thought about one file
system with all the representations
... for the same content in one file. I said no not now.
... Then I realised you can put the root element of each
document in a parent container,
... and get this with a separate "TTMLContainer" element whose
children are tt elements.
<Yam_ACCESS> +present
Andreas: I wondered if this is a more generic use case where
you want to specify something.
Nigel: One option available in TTML2 is to use the condition
mechanism to extract just
... the content for, say, a specific language, and put all the
different content in a single TTML document.
... That's an alternative to what you suggested.
... Another is to use a different manifest format, like IMF etc
to handle this kind of case.
Glenn: I would have answered "yes of course" and it's the
responsibility of the application
... that's using TTML to define how to use it. It's something
external to the TTML file.
... I would refocus the question on making that an application
specific usage scenario.
... Like if you want a PNG, JPEG and SVG version of a single
image, there's no requirement
... for each file to know about each other but the outside
usage may have a manifest of
... potential realisations of that resource.
... This is like the semantics of URNs and URIs. URIs are
abstract, and URNs more so, but they
... map to one or more URL that realises the resource, and each
URL might have a different
... aspect like language and so forth.
Andreas: I know that we delegate this. What Nigel said is to
pick something out of the file
... but you want to store it without picking something. You
don't want to say which one is
... preferred. You could specify the condition for a default to
be selected.
Nigel: True
Andreas: The other storage scenarios are too big. It depends on
the overall system
... environment if they use IMF or something else. I don't
think it makes sense just to store
... subtitles in IMF without the video.
Nigel: It begs the question why localise subtitles only and not
other resources like audio,
... and if you are localising audio, then it starts to make
more sense to use something like IMF.
Andreas: You may have the problem that you want the different
subtitle versions in one
... file. The condition attribute is an interesting thought to
check out. It is not in IMSC?
Pierre: No.
Andreas: The easiest one is just to have multiple TTML
documents in one file. Then you
... can easily access the complete document tree and switch
easily between different documents.
... Then from one big file you can generate easily a separate
document just for one version
... or language.
Glenn: I don't like it at all.
Nigel: Don't like what?
Glenn: Multiple TTML documents as children of a parent element.
It raises all sorts of
... questions about semantics, like do they all start at the
same begin time.
... It is more reasonable that applications of TTML should
define their own way to manage
... groups of TTML documents.
Nigel: That sounded contradictory - do you mean it's okay for
an application but not for this group to do?
Glenn: Yes, for example you could just put them in a zip file.
Nigel: Yes and give each a language-specific filename.
Glenn: Right [cites an existing example of this kind of
technique]
... It seems too closely aligned to specific application
requirements, for example what is
... the criteria for semantically grouping? Right now we define
three different root level
... element types, actually four, that can appear in a TTML
document: tt, ttp:profile, isd:sequence and isd:isd.
... The isd:sequence is a bit like what you're suggesting
except you're suggesting a group
... not a sequence.
Andreas: The use case could be that you have one file and a
player like VLC offers the choice
... of languages, and the same file would work in other players
too. Two broadcasters
... mentioned this to me recently, and others before. The
scenario exists, and operational
... people are looking for something like that. They can come
up with their own solution,
... the question is if a common solution makes sense.
Glenn: In HTML there's something called a "web archive" that a
lot of tools can work with,
... which saves all the page's files together in some form.
... I've never seen any proposal within W3C to define a
standard container for a collection
... of HTML files, or PNG files or whatever basic content
format file is being defined.
Andreas: The video element can have multiple text track child
elements.
Nigel: I would push back against this because I think that the
use case of localisation
... goes beyond just subtitles, and should include all media
types as first class citizens,
... audio, video and anything else. It's detrimental to be too
specific.
... Thanks, it seems like we don't have consensus to develop a
requirements document
... for grouping TTML documents at this stage.
Additional styling
Nigel: I wanted to raise this because we have an interesting
use case in the BBC that
... TTML cannot currently handle, even though it seems like it
should be able to.
... [demonstrates some internal pages showing TTML presentation
of narrative
... text captions in video styled with CSS, animations,
borders, border gradients etc.]
... At the moment the CSS properties we would need are specific
borders, clip-path and
... background linear gradients.
... I'm much more worried about future CSS properties that
would be needed though.
Glenn: There are a couple of problems. One is testing - if we
have a generic pass-through
... mechanism, like a "css" property, whose value is a CSS
expression, what do you put in
... your profile? Right now we don't have a notion of
parameterised set of values.
Andreas: In general I like the idea to use CSS features before
they enter TTML properly.
... I don't know how exactly, but in general I would support
figuring out how this could work.
Glenn: It is worth investigating.
Pierre: Since the alignment has been with CSS it is worth a
longer discussion.
... Just in names there's friction for some folks, even though
the gap is reducing. I also
... like the way it is clear you don't have to import all of
CSS, which is a relief to others.
... For a computer, mapping a TTML name to a CSS name is a
no-op. Alignment between
... TTML and CSS has served us well so we should continue doing
it.
Glenn: It would make it easier to expose CSS properties without
the expense of a TTML
... style attribute. There may be a sacrifice of
interoperability.
Andreas: This group would just define the mechanism and then it
is the responsibility
... of the application if it supports it or not.
Glenn: Then there's the profile mechanism issue.
Andreas: Just say nothing about it.
... [leaves]
Pierre: [leaves]
Nigel: Thank you both.
... OK for this requirement, I think it is worth spending some
time describing the
... requirement more fully, which I will try to do. Obvious
solutions to this kind of thing
... include specifying CSS properties directly on content
elements or style elements,
... and allowing a class attribute to define CSS classes that
apply to a content element.
... I realise both of these could create clashes between TTML
styling and CSS styling and
... we would need some mechanism for resolving those clashes.
Especially class styling
... is very different to the applicative styling we have in
TTML, since it goes the other way
... in terms of traversal.
Glenn: Class is a shorthand for id, and we already have id.
Nigel: It's not a shorthand for id
Glenn: You can have a CSS stylesheet associated with a TTML
document and have #id styles
... that are associating elements in TTML with CSS. In that
sense adding class is just a
... shorthand for aggregating multiple ids into one group.
Nigel: That's true.
Glenn: At application level you could put a CSS stylesheet on
one side.
... There's a precedent here in WebVTT of applying a stylesheet
on the outside, though it
... it not defined clearly. Then it becomes a player dependent
function whether it ingests
... and uses the stylesheet during the formatting process.
... Especially if you are doing a process where you're
converting TTML to HTML/CSS.
... I would be reluctant to buy into an approach that requires
mapping to HTML and CSS.
... Provided that we can have native implementations or things
that don't map to HTML/CSS
... and still use whatever we develop here that would be my
mental model for acceptability.
Nigel: Just wondering about how big a problem space I'm opening
up. If we map TTML
... to SVG do we have to define how any classes or styles are
tunnelled through?
Glenn: It could be done, the implementation would need to do
some book-keeping as it
... goes through the area mapping process, to get to the SVG
elements that can be styled.
... One TTML element can generate multiple areas and you can
have multiple TTML elements
... generating one area.
Nigel: In terms of spec work should we feel obliged to define
the tunnelling into SVG?
Glenn: I don't think so.
... We just need to be careful not to impose a restriction to a
particular mapping format.
... It should be possible to make a native implementation that
doesn't use CSS or SVG.
... In such a situation the native player would have to
interpret the CSS and do what CSS
... does in that circumstance. A lot of CSS semantics are based
on the box model and there
... may be some minor impedance mismatches between our area
model and the CSS box
... model.
Nigel: I take your word for that, but our model came from
XSL-FO, which was at least once
... aligned with CSS.
Glenn: For example CSS doesn't allow width or height to be
specified on non-replaced
... inline elements whereas we do allow that for ipd and bpd on
a span, even if it does not
... have display "inline-block". I just wanted to mention that
we have taken various
... decisions semantic-wise where if we just expose CSS into
the mix we may have to deal
... with incompatibilities that might arise.
... One answer to the implementer is "do whatever makes sense"
which is generally how
... implementers operate anyway, but then you get interop
issues.
Nigel: That's the point, to make an extensible model that
allows a greater variety of CSS
... styles to be applied in applications that can support them.
... For example we could put all the "CSS tunnelling" semantics
behind a feature designator.
Glenn: Yes. The general approach for CSS is that
implementations ignore what they do not
... recognise. There are no guarantees.
Nigel: Some implementations support @support queries, but older
ones might not.
... I think we have consensus to work this up in terms of
requirements and head towards
... a solution in some future version of TTML.
Audio Profiles
Nigel: I presented something here to the joint meeting with the
Media and Entertainment IG
... yesterday, and there's an Audio Description CG meeting on
Thursday.
... For this group's benefit, the idea is to create a profile
of TTML2 which supports the
... features needed for audio description.
[18]Presentation to joint meeting
[18] https://www.w3.org/2011/webtv/wiki/images/3/30/AD_CG_presentation_TPAC_2018.pdf
Nigel: [shows TTML2 feature list]
... I've just been told that the BBC implementation is live on
github.io, but not quite working yet
[19]BBC Adhere implementation
[19] https://bbc.github.io/Adhere/
scribe: It has some build issues to fix.
... My intent is that when the CG is settled on the profile we
add it to the TTWG Charter
... as a Rec track document.
Glenn: During the drive up to the implementation report you
mentioned some challenges
... and we made changes to some of the feature definitions - we
removed embedded-audio
... from the audio-description feature. Was that due to an
implementation constraint?
Nigel: We made different changes. The embedded audio was one
where I wasn't sure if
... we would hit time limits. The other was text to speech in
conjunction with web audio,
... which is an API limitation that web speech output is not
available as an input to web audio.
Glenn: Can that be rectified?
Matt: I had a response about this a couple of weeks ago. Due to
licensing of some of the
... recognisers and synthesisers in the Web Speech API they are
not licensed for recording
... so there was little enthusiasm for making an API call that
would capture speech output
... from the API. Of course there are other ways to do it, but
making it a feature would
... open it up to licensing issues.
Nigel: The Web Speech API never got towards Rec, it's a Note I
think.
Glenn: Generally IPR isn't an issue for W3C specs.
Matt: It has multiple implementations but is still a CG report.
... The "terms of service" for many voices allow use in real
time but prohibit recording the
... audio and saving it for later playback.
Nigel: If we can encourage that to get to resolution then we
could use it for AD.
... The other issue to note is that for embedded audio, there's
a bit of a challenge
... implementing clipBegin and clipEnd. For normal audio
resources you can use media
... fragments on URLs to make a time range request, but in our
testing it didn't seem to
... honour the end time always, just the begin time. But more
seriously for embedded audio,
... if you implement it as a data: url then those URL media
fragments seem to be completely ignored.
Matt: Range requests have to be supported by the server I
think. Most do, but it's not a given.
... The data URL may not be supported at all.
... The response has to have the accept-ranges header set.
<mdjp> range requests
[20]https://developer.mozilla.org/en-US/docs/Web/HTTP/Range_req
uests
[20] https://developer.mozilla.org/en-US/docs/Web/HTTP/Range_requests
Nigel: I think this is a different thing. It's byte ranges.
[21]Media Fragments URI
[21] https://www.w3.org/TR/media-frags/
Nigel: That's what I meant.
... It allows for a url#t=10,20 for example to give everything
between 10 and 20s. In testing
... that doesn't seem to work with data urls.
... That's something that may need an explicit mention in a
future edition of TTML2, for example.
... While we're on future editions of TTML2, and audio, I hope
to be able to define the
... audio processing model more normatively than it is now.
... The Web Audio spec is in CR at the moment, isn't it?
Matt: Yes. Timeline to be discussed in the meeting on Thursday.
No issues have been
... raised, we're not aware of any problems. On a similar note
I should say we're meeting
... on Thursday and Friday, which conflicts with the AD CG but
the main topic will be
... use cases, requirements and features that have been omitted
from v1 so if there's anything
... around this work that would require Web Audio work to
facilitate it now would be a good
... time to provide them.
Nigel: Thanks for that, if any arise I will let you know!
Glenn: Back on the issue of speech, I had pointed out how in
TTML we defined a special
... resource URL for output of the speech processor, and how
that was intended to be
... potentially used as an input to the audio element, so you
could say an audio element
... is the speech resource instead of a pre-defined clip, and
that would be useful for mix
... and gain operations.
Nigel: It's unnecessary - we didn't need to use that in our
implementation.
Glenn: The connection between the speech processor's output and
the audio node
... hierarchy does not exist.
Nigel: We take it as an implied one.
Glenn: That's an implementation choice that I didn't intend in
the spec.
Nigel: That seems to be unnecessary pain - if you bother to put
tta:speak in as anything other than none
... then you obviously want to generate audio.
Glenn: You need it to be able to pan the speech output, for
example.
Nigel: That's true, I didn't consider that.
... You could posit an implied anonymous audio element if the
span's tta:speak is not "none" and there is no explicit audio
element child.
Glenn: That's a bit like putting origin and extent on a content
element!
Nigel: I sort of see what you mean [scrunches eyes]
Glenn: In the definitions section I define a speech data
resource.
Nigel: It doesn't seem clear what happens if tta:speak is not
"none" and there is no
... audio element child.
... It is possible that we can tidy this up in a future
edition.
Glenn: It could be improved - we could tie it to that binding
mechanism more explicitly.
Nigel: +1
... However I would like to see a syntactic shortcut that
avoids the need to have an audio
... element with a long string in it just for "mix this audio"
when tta:speak is set, because
... that's obvious.
Glenn: I notice that it is not possible to add audio as a child
of body, in TTML2. Why not? I don't recall my logic there, if
there was any.
Nigel: I think it's clear that there's a bucket of
audio-related potential improvements that
... are most likely to come out of work in the AD CG, which we
should consider for a future
... edition of TTML2.
Meeting close
Nigel: Thank you everyone, we've reached the end of our agenda
for today.
... We should take a moment to celebrate the success we've had
in all the work we've done
... on TTML and IMSC over the past few years!
... Next week we have no weekly call, the week after I will
send an agenda as usual.
... [meeting adjourned]
Summary of Action Items
Summary of Resolutions
1. [22]As part of the request to publish TTML1 3rd Ed as a
Recommendation we will supersede TTML1 2nd Ed.
[End of minutes]
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Minutes manually created (not a transcript), formatted by
David Booth's [23]scribe.perl version 1.154 ([24]CVS log)
$Date: 2018/10/23 15:14:03 $
[23] http://dev.w3.org/cvsweb/~checkout~/2002/scribe/scribedoc.htm
[24] http://dev.w3.org/cvsweb/2002/scribe/
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Received on Tuesday, 23 October 2018 15:19:31 UTC