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April F2F Meeting minutes

From: Nigel Megitt <nigel.megitt@bbc.co.uk>
Date: Wed, 22 Apr 2015 12:27:50 +0000
To: TTWG <public-tt@w3.org>
Message-ID: <D15D5252.1ECFF%nigel.megitt@bbc.co.uk>

Minutes for our face to face meeting on 9th and 10th April are now
available at http://www.w3.org/2015/04/09-tt-minutes.html and
http://www.w3.org/2015/04/10-tt-minutes.html respectively. Thanks to
everyone who was able to make it for a very productive two days.

Please note that I've been able to attach whiteboard images for the time
diagrams on the 9th, but don't have images from other times when people
drew on the board; hopefully the concepts were captured adequately in the
transcript. If you captured images that I didn't and you'd like them to be
added please send them to me.

Text versions of the minutes are:

Day 1:


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

                               - DRAFT -

                Timed Text Working Group Teleconference

09 Apr 2015

   See also: [2]IRC log

      [2] http://www.w3.org/2015/04/09-tt-irc


          glenn, nigel, atai2, pal, dakim, tmichel, Courtney





     * [3]Topics
         1. [4]Agenda for this meeting
         2. [5]TTML2
         3. [6]TTML2: timing
         4. [7]Spatial and Layout
         5. [8]ipd and bpd
         6. [9]Condition structure
         7. [10]Recap
     * [11]Summary of Action Items
     * [12]Summary of Resolutions

   <scribe> scribe: nigel

Agenda for this meeting

   group: Introductions

   tmichel: Thierry Michel, staff contact W3C

   nigel: Nigel Megitt, BBC, chairing

   glenn: Glenn Adams, Skynav, Editor TTML

   dakim: Dae Kim, Netflix, observing

   atai2: Andreas Tai, IRT

   pal: Pierre Lemieux, Movielabs

   courtney: Courtney Kennedy, Apple

   nigel: Runs through planned agenda; topics and agenda.

   pal: I have some comments to raise on TTML2 that I think
   overlap with the existing topic list

   Courtney: I'd like to raise future work in WebVTT specifically
   Japanese script display

   nigel: I propose spending day 1 on TTML2 and day 2 on IMSC 1
   and WebVTT and future stuff,
   ... with some time at the end to revisit any topics that we
   want to.

   group: Happy with that.

   nigel: AOB?

   group: No AOB


   nigel: Actions - there's nothing to discuss here
   ... Issues - there's no work on open TTML2 issues since the
   last meeting

   glenn: In the TTML2 ED there are Editorial Notes, Issues and
   "to be defined" things listed.
   ... I've put them into a spreadsheet and classified them as
   Editorial (no technical thought needed),
   ... Technical (requires technical effort) and "X" (needs
   example materials). There are 105 items
   ... in the spreadsheet.
   ... Out of those 105 around 2/3 are Technical, and 1/3 are
   mostly examples with a few pure editorial things
   ... This is forming my task list




   nigel: I suggest we go through the TTML2 change topics and call
   out these spreadsheet changes
   ... where needed.
   ... First topic is profiles - especially to support the
   registry of TTML flavours

   glenn: There are some changes here in §5.2, §6 and Appendix D
   ... There are two issues Issue-351 and Issue-352


   <trackbot> issue-351 -- Update IANA registration for TTML2 --


     [14] http://www.w3.org/AudioVideo/TT/tracker/issues/351


   <trackbot> issue-352 -- Add Media Registration Annex -- open


     [15] http://www.w3.org/AudioVideo/TT/tracker/issues/352

   glenn: The first of those listed is to restore and update the
   Media Type Registration
   ... That was Issue-352. The second is Issue-351, which is to
   define the syntax for processor profiles
   ... I don't believe there's anything needed for discussion
   here. I think we've done that.

   <glenn> [16]https://www.w3.org/wiki/TTML/CodecsRegistry

     [16] https://www.w3.org/wiki/TTML/CodecsRegistry

   glenn: Syntax could be something to discuss
   ... You can express with this simplified syntax what can also
   be expressed in the profiles
   ... mechanism that's in TTML2
   ... Stepping back a little, I want to check that we have an
   understanding that this parameter is
   ... specifying what processor is required in the mind of the
   author to be able to process this document
   ... as opposed to making a declaration about the content
   profile that is followed. Is that a shared understanding?
   ... The content profile states what features have been used
   whereas the processor profile can be potentially
   ... inferred from the content profile, and says 'this is what I
   need the processor to be able to support'.

   tai: They're not the same.

   glenn: No, you might say that a processor that is a superset or
   even a subset is adequate.

   tai: From a different perspective, people approached EBU and
   TTWG with a requirement to distinguish the
   ... different documents with respect to which specifications
   the document conforms to, and want a mechanism
   ... to describe this. I saw this more as a content profile not
   a list of processor requirements. More to say "this
   ... document I guarantee conforms to SDP-US, IMSC or whatever"

   glenn: That's orthogonal to what the processor needs to
   support. The only reason I can see for declaring a
   ... content profile is for validation processing. For
   non-validating processors it's therefore not relevant. The
   ... only potential relevance is to infer a processor profile
   from it. If a document only has a content profile
   ... declaration but no processor profile declaration then it's
   possible to infer a maximal processor profile.

   nigel: My recollection from the previous discussion is that the
   main use case is for MPEG-4 signalling of what
   ... processor is needed, which I think came from David Singer.

   tai: Will this also work for TTML1 derivatives too?

   glenn: The higher level syntax to allow operators and
   combinations, but if you ignore that and make it a simple token
   ... e.g. "stpp.C", when we discussed this codecs registry what
   we said is that it would be a mapping from a set
   ... of small identifiers to their corresponding designators
   that are externally defined. I had seeded the table
   ... on the wiki page with the original TTML1 profiles and the
   SDP-US profile. The identifier in the left column
   ... was the short value in place of e.g. "C" above it could be
   "tt1p". Notice I included the version number in the
   ... short identifiers. So if you want an implementation that at
   least supports the original TTML1 profile as
   ... originally defined then you could use the short code in
   there. What we haven't done yet is to add the new
   ... TTML2 profiles, which there are 3 of, and we haven't added
   any industry profiles like EBU-TT-D etc.
   ... All of these profiles do go back to TTML1 so from that
   perspective this solution will be valid.

   tai: When can this be used?

   glenn: The only thing we need to update in the registration is
   the extra parameter.

   tai: What we need to be able to say is when people can use

   glenn: The syntactic aspect of it is something that has to
   involve IANA. The values used within it can be
   ... offloaded to the registry on our wiki.
   ... It's somewhat complicated by the optional parameter in the
   original registration of "profile"
   ... We used the term "document profile" to mean processor
   profile, which is confusing.
   ... ttp:profile takes as its argument an xs:anyURI value that
   can be relative or absolute.
   ... There are two things that are different in the new
   proposal. 1) The syntax and 2) to use short codes not URIs
   ... This allows for shorter labels and a public registry for
   people to register mappings between identifiers and
   ... URIs, and therefore to make known publicly specifications
   of profiles.

   tai: So the ttp:profile could be used already?

   glenn: Right, and it needs to match the URI syntax of

   tai: To use this existing profile, that's a debate that's been
   used several times in the past. Do you need a
   ... complete profile document or...

   glenn: It can be prose only.

   tai: So we can use this mechanism already?

   glenn: That's correct. In TTML1 it may be "any URI that
   feasibly dereferences a profile definition document."
   ... That means its potential but not necessarily. Also that
   document can have no content other than its URI.
   ... It could be a one line profile that is a formal profile
   definition document with no child elements that refer
   ... to any features. All of the definition could be in prose in
   that document. In that sense it's just a pointer.

   tai: This is what people are looking for at the moment. We
   could use it already for EBU-TT-D?

   glenn: You could use that today if you don't want to do

   tai: And there's no need to register any designator?

   glenn: The only requirement is that it doesn't use the TT
   namespace as a prefix. Other than that it can be any URI.

   nigel: Two other requirements that were raised before are to be
   able to signal multiple processors that can
   ... process, and also to use short codes.

   tai: It's good to know what we can use now.

   glenn: You can signal a forward path using the current profile
   parameter and moving to the new mechanism.

   tai: That sounds good.

   glenn: There's already a note in TTML1 that says that
   processors do not need to be able to dereference the URI.

   nigel: Stepping in with a bit of chairing, I'm hearing that
   there's no technical objection, the editorial requirements
   ... are clear and that there's a forward path for TTML1
   profiles. Is that fair?

   group: agrees.

   nigel: Let's take a short break.

TTML2: timing

   nigel: Glenn has a couple of entries in the spreadsheet here.

   pal: see my email at

   ... basically, what is the relationship between the timings and
   the media?

     [17] https://lists.w3.org/Archives/Public/public-tt/2015Jan/0114.html

   glenn: There are lots of issues here! There are lots of
   potentially different clocks at work.
   ... Also there may be no related media object.

   pal: Okay let's start with that.

   nigel: Media timebase?

   pal: Let's start with that as the simplest most common example

   glenn: Terminology is an issue here obviously.

   nigel: I have quite a clear view of what the current spec
   means, so I'm interested in exactly what questions arise that
   are maybe not so clear.

   tai: I agree that there are questions that keep arising.

   pal: So nigel could you draw a diagram showing the relationship
   between media offset, root temporal extent, etc.?

   nigel: I'd rather not because I object to using mediaOffset!

   glenn: That's a separate topic.
   ... We have made some progress in clarifying what we brought in
   from SMIL. Appendix M is one such attempt,
   ... but falls short of nailing down everything. What we need to
   do is to nail down exactly what you asked in
   ... your question. Recently I've had questions about the
   computed body duration vs the implicit body duration.
   ... Does the computed time become the time of the related media
   object's duration? If there's no related media
   ... object is the computed time of the body related solely to
   the timestamps in the document?
   ... The reason for mediaOffset in my mind was to address the
   condition where content is authored for
   ... arbitrary or dynamic differences between the timeline of
   the related media object. This comes up with SMPTE
   ... timeBase especially e.g. should people put begin="0" and
   offset of 10 hours to get to "10:00:00" as a start
   ... and there's another example with negative times.

   tai: What I think would be helpful would be for readers to have
   this picture.
   ... Appendix M is a good start but some images might be

   nigel: Draws a picture. Question arises as to the
   impact/meaning of Root Temporal Extent.
   ... My interpretation is that the root temporal extent begins
   at the earliest computed begin time and ends at the
   ... latest computed end time.
   Photo of whiteboard with time graph

   "RTE" is shorthand for Root Temporal Extent. Calculation on
   left shows computed duration in this example is 4-1=3.

   glenn: For media timelines I would begin every root temporal
   extent at zero [looks at spec] ... but the spec
   ... has it more like your interpretation nigel.

   pal: The next question is what is the implicit duration?

   nigel: I generally don't have a usage for this, but there is a
   specific case where it comes in. Consider a body
   ... with a dur attribute but no begin and end attribute, and
   simple, untimed content. The resolved begin time
   ... is whenever you make the document active and the resolved
   end time is that resolved begin time + the dur
   ... attribute.
   Photo of whiteboard showing interpretation of body with dur and
   no begin

   glenn: Part of the problem is that we also have to deal with an
   event based model.

   <tmichel> SMIL Descriptive terms for times



   glenn: What's the difference between implicit duration and
   active duration?
   ... TTML 1 says that the implicit duration is indefinite, in
   §10.4, and that's in TTML2 §12.4.

   nigel: For me this is a feature of par timeContainers where the
   begin and end times of a descendant element
   ... relate to its parent, and that nesting construct applies
   both to content elements and to TTML documents
   ... themselves relative to some external playback.

   glenn: Under the SMIL 3 timing and synchronisation module
   there's a table defining the simple duration
   ... We don't have repeatDur and repeatCount so in TTML they're
   always unspecified.
   ... Then there's an algorithm for computing the active duration
   which defines some maths, and then
   ... the "active duration algorithm". I've implemented all this
   in code.

   tmichel: Also there are some descriptions in §5.7 of SMIL 3.

   pal: It already helps to know that "implicit duration" has a
   meaning in SMIL. Maybe it's just a matter of
   ... condensing in one place in the spec exactly how the TTML
   attributes apply to the SMIL model.

   glenn: We originally based the timing syntax and semantics on
   SMIL taking into account the SMIL specific way
   ... to include SMIL in other specifications. We overrode some
   aspects of it. We didn't want text to have an
   ... implicit duration of zero for example - we made it
   indefinite so that untimed text expands out to its
   ... container's duration. That's what TTML1 §10.4 and TTML2
   §12.4 do.
   ... You have to go back to the SMIL timing model to define the
   timing model as we intended it. If we were
   ... to pull it out it would take quite a lot of work, i.e. to
   remove the dependency on SMIL.

   tai: It made it difficult for the EBU group for example to look
   into SMIL, and it's a generally difficult task to
   ... read and understand SMIL. I think this is a generally
   difficult topic to understand. It would make it easier if we
   ... can allow people to understand the timing model without
   reading SMIL.

   glenn: A similar thing arises with formatting semantics - we
   did the same thing there where we reused XSL.

   pal: If the document says "all the semantics of SMIL apply
   except where specifically stated" and then we
   ... highlight SMIL terms and where there's a difference then at
   least it helps a reader to figure out where to look.
   ... I share the concern that SMIL is difficult to implement and
   that timing is central to TTML.

   glenn: I can't disagree with any of that - people have been put
   off by SMIL, which is hard to get your head into.
   ... We did what you suggested part way, e.g. on the definition
   of begin, end, dur and timeContainer, where
   ... we say that the semantics are based on SMIL.

   pal: Maybe provide a nice diagram like the one Nigel has drawn
   to show this.

   nigel: I don't mind drawing some pictures here, but they should
   be non-normative.

   glenn: We need to consider what is currently broken, e.g.
   mediaOffset which I thought was needed. Also a
   ... reader education effort to explain the model in a more
   accessible way to understand the complexity without
   ... having to dive into SMIL. The first is necessary for us to
   get into the spec right away. The second part
   ... technically doesn't need to be in the spec but if we can
   make a straightforward improvement in out time
   ... frame then let's do that.

   pal: It would be useful even to clarify the meaning of Root
   Temporal Extent in terms of SMIL for example.

   glenn: If RTE is the difference between the latest and the
   earliest resolved time coordinate in the document
   ... then we can state that.

   nigel: I don't think that would cause any difference, for RTE =
   resolved begin -> resolved end

   pal: Is that an action to change the spec?

   glenn: I would like to have a few diagrams. You can overdo them
   - the question is what do you want to
   ... communicate. Since we've been focusing on media timeBase,
   at a minimum we probably want to have a
   ... diagram that shows some of this working in the media
   timeBase. The diagram may look different for other
   ... timeBases.

   nigel: It does, and I can show how. For smpte you have to look
   for specific timecode values.

   glenn and nigel: some discussion about mapping smpte
   discontinuous into a continuous mode and mapping
   ... smpte into media; need to be careful in case smpte is being
   used so the TTML document survives media edits

   glenn: If we think we can translate the other timeBases into
   media then having diagrams for media time
   ... gives the most value.

   tai: The media timebase view would be helpful.

   glenn: We don't need it normatively.

   tai: Exactly. Also, it helps readers to understand the context
   operationally, and why different models might be useful.
   ... If you can do this trick and connect to daily operation
   then it will be easier for them to understand.

   nigel: I'm happy to take an action to create some diagrams, but
   I'm not sure what the set of concepts is that
   ... need to define on that picture.

   pal: I'd also like to clarify all the SMIL time references.
   ... The example you've drawn is incredibly useful because it
   helps point to a problem with containers, that
   ... say "start playback 5 seconds into the media" where the
   media is TTML with no begin and end values.
   ... There's an unresolvable infinite loop.

   nigel: We can solve that with a normative statement I think. It
   could be to require a begin attribute on something, for

   pal: That could help for IMSC 1 for example.

   Courtney: It might be a nice simplification.

   pal: If a document has a body with no time attributes and a p
   that begins at 10 hours, and the intention is
   ... to start playback at the beginning of the media then you'd
   better have a container that says 'start playing
   ... 10 hours in'.

   nigel: Right.

   glenn: That's why I wanted a mediaOffset parameter.

   nigel: That's a container issue not something that should be in
   the TTML, IMO.

   pal: It would be useful to clarify that in the media timeBase
   time 0 always corresponds to the beginning of the
   ... media.
   ... [draws a typical containment scenario where the media
   container defines relative offsets between video and TTML]

   glenn: In my mind the mediaOffset was metadata to indicate some
   information in the absence of external
   ... container information. I would still resolve that example
   as saying that the document contents begin at
   ... 10 hours, and the timed text timing model doesn't care
   about how the synchronisation works.
   ... If you want to allow negative times and apply some
   arbitrary time in TTML in addition to the container
   ... offset then that's another thing.

   nigel: I would say that we should not do that. It's actively
   unhelpful to have this information potentially in two
   ... places.

   pal: The ultimate synchronisation/resolution of the timing is
   set by the container.

   nigel: And that's unavoidable.

   pal: Right. It's only when you bring it back in with a
   container that you can actually combine this stuff.

   glenn: So if you had a way to say "in this TTML we think the
   related media object starts 1 hour in"...

   pal: I think that would be ignored.

   nigel: You have to think about the encoder/packager.

   pal: You could just look at the first time value?

   nigel: No, because the intent might deliberately be that the
   first subtitle begins 5s into the media.

   pal: Okay then you do need that.

   Courtney: You need this in order to create the container and
   package it up.

   glenn: We could include this as metadata then.

   nigel: Yes you could do.

   pal: I think that metadata could be useful but you can't
   normatively apply it because there may be cases where
   ... after creating the TTML the video is edited or further

   nigel: +1

   glenn: If you see an arbitrary TTML document and the first
   resolved begin time is 1 hour in you can't tell if
   ... that's intentional or not.

   nigel: Exactly. It could be the second 1 hour long sample of
   TTML for a longer thing.

   glenn: Yes.

   tai: Does this happen in real workflows, that the video is
   edited or offset?

   Courtney: You might have a late delivery scenario where the
   video sent to the caption author isn't the same
   ... version as what's played out, exactly.

   pal: You can't guarantee that the end point video is exactly
   the same.

   tai: So you have to define in an external context what the
   offset is.

   Courtney: I agree. Whoever is packaging it up has to make those

   pal: So you might require in a workflow that the relative
   offset compared to the media originally supplied is
   ... indicated.
   ... And then you have the other challenge that the package
   indication of frame rate might differ from what
   ... was used when the document was authored, e.g. a 23.98 fps
   video referred to as 24 fps.

   nigel: Right, and we resolved that with metadata in EBU-TT-D to
   indicate exactly that scenario, so that at least
   ... there's a heads up for the packager that there could be a
   problem, because the time expressions don't
   ... necessarily use frames.
   ... I've created an issue for this.


   <trackbot> issue-381 -- Clarify timing concepts in relation to
   SMIL -- raised


     [19] http://www.w3.org/AudioVideo/TT/tracker/issues/381

   reopen issue-381

   <trackbot> Re-opened issue-381.

   nigel: let's break for lunch.
   ... and we're back...

   pal: I like the idea of defining root temporal extent in terms
   of resolved begin and end times

   issue-381: Also define the root temporal extent in terms of
   resolved begin and end times

   <trackbot> Notes added to issue-381 Clarify timing concepts in
   relation to SMIL.


   <trackbot> issue-382 -- Require a computed non-indefinite begin
   time -- raised


     [20] http://www.w3.org/AudioVideo/TT/tracker/issues/382

   reopen issue-382

   <trackbot> Re-opened issue-382.

   nigel: For reference, the issues regarding media offset and
   media begin are issue-361 and issue-270
   ... There's one more point on timing I wanted to raise before
   we move off, which is the reference clock
   ... when timeBase="clock" and clockMode="local".

   glenn: It's obvious what the intent was here - it's whatever
   clock is on the wall. It's the real time in the local time

   tai: So if someone sends you a document with local time then
   you don't know which local time they mean.

   pal: What's the use case?

   nigel: For example you have a reference clock source that's
   used to time media playback and you want to
   ... capture subtitles with times using the same clock source.
   Your definition of local time is independent,
   ... and you need some kind of identifier e.g. a PTP server, to
   be able to connect the recorded media with the
   ... TTML document.

   glenn: That sounds application specific. Are you also saying
   you want to know the local time offset relative to UTC?

   pal: If you know the UTC offset then why can't you just specify
   times in UTC?

   glenn: So to be clear the intent is for playback only not
   recording time. So the idea is to say here's some timed
   ... text that doesn't have a related media object, or if it
   does then the synchronisation is out of scope.

   nigel: But you can't detect that intention from any wording in
   the spec. It looks symmetrical regardless of
   ... whether times are captured times of recording or of
   intended times for presentation.

   pal: So if something is synchronised locally with a local clock
   then it will work fine. The second you export the
   ... TTML document with a local timestamp I have no idea what
   that means - is it a local time against your watch,
   ... an atomic clock, or what. If you want to send it to me you
   need to convert the timestamps to UTC.

   glenn: In SMIL the syntax for time expressions includes
   wallclock sync value. We modelled our local, utc and gps
   ... timebase on that wallclock value. Local in this case means
   the same as wallclock in SMIL. We extended it
   ... by adding UTC and GPS. If you change local to wallclock
   maybe that's clearer what it means.

   nigel: That restates the ambiguity but doesn't resolve it.

   glenn: It's easy enough for us to add something normatively
   about this, to say it's intended to mean the commonly
   understood wallclock value.

   nigel: I don't want to do that though. Would you add a new
   clockMode e.g. "reference" and some metadata
   ... to identify the clock source?

   glenn: We could do that.

   nigel: I don't think we need that though. We could just add an
   interpretation of local that allows it to be
   ... parameterised with a reference clock source for example.

   glenn: Since we were vague about it I don't see why we
   shouldn't constrain it to mean what we mean it to mean.

   nigel: I'll add an issue to add this then.

   tai: We (in EBU) have a need to define a local parameter
   localTimeOffset. There has been discussion and a use
   ... case identified for that. Another issue I could imagine is
   when you have two files relating to the same source
   ... media that's recorded and you put timeBase="clock" and
   clockMode="local" and then there's a summer time
   ... shift part way through the document, how can you translate
   to media time without knowing the timezone.
   ... For IRT we don't have that specific scenario but I think
   there are use cases from broadcasters in Europe that
   ... would need that extra information. We will define it in
   EBU, the question is if its useful in TTML more generally.

   nigel: I would argue that it is, of course.

   tai: We don't have an official request from EBU to add this,
   but we seem to be the main group member that
   ... thinks its useful.

   pal: So you have two documents created by the same closed
   system one before a summer time shift the other after.
   ... When you export those, convert them to UTC! Don't send me a
   document with local times in.
   ... As a data point, in digital cinema local times have been a
   big source of confusion. My advice is just use UTC.
   ... The timezone adds nothing. It's just an offset relative to
   UTC, which changes locally in strange ways.

   tai: You can still do that if you specify the offset correctly.

   pal: My recommendation is just use UTC because then we
   definitely agree. Otherwise you have to keep track of DST.

   nigel: But if you send qualified ISO 8601 times then the offset
   is clear regardless of DST.

   pal: Yes, you can do that but my recommendation is don't even
   add offsets.

   tai: I'm not sure if I agree because if for example you use the
   xs:date and xs:time schema formats in XML
   ... which define this kind of information that would be easy
   and does allow offsets to be included. It's easier
   ... not to make exceptions.

   nigel: But we don't use XML date and time formats in the

   glenn: No we didn't define a schema with respect to date and
   time expressions.

   tai: It's the same. If you put local and put this time zone
   then it would be the same as using UTC.

   nigel: I've added issue-383 for this.


   <trackbot> issue-383 -- Clarify the application specific usages
   of clockMode="local" -- raised


     [21] http://www.w3.org/AudioVideo/TT/tracker/issues/383

   reopen issue-383

   <trackbot> Re-opened issue-383.

Spatial and Layout

   nigel: We have ttp:pixelAspectRatio and ttp:storageAspectRatio
   as well as the new tts:position attribute.

   pal: The reason I brought this up is that IMSC 1 has some
   language that we should make sure is consistent
   ... with TTML2, and also because there are lots of TBDs in
   TTML2. Maybe we're not ready for this yet?
   ... Last time I looked this wasn't well enough defined in the
   spec to come up with a conclusive interpretation.

   glenn: [goes to the whiteboard]
   ... In TTML1 we have tts:extent and tts:origin on regions. We
   have extent also on the root element tt:tt.
   ... We defined an implicit origin for the root element in the
   absence of external information. What this didn't
   ... do very well was to situate the extent of the document
   inside of a media element since it defaulted the
   ... root region to the top left without any considerations of
   aspect ratio or centering at all. In IMSC you define
   ... some default extent and origin sets to center the root and
   allow it to be contained within the related media
   ... object's extent while maintaining a certain aspect ratio.

   pal: There's another mode, if you don't specify
   ittp:aspectRatio, which is to fill the entire region. If you do
   ... specify it then it fills the root container while
   preserving the aspect ratio.
   ... This is defined in IMSC 1 §6.7.1 (in the ED)
   ... It says preserve the aspect ratio and do it to make the
   width or height equal to that of the media object.

   glenn: In this case the aspect ratio is effectively the display
   aspect ratio not the storage aspect ratio.

   pal: I think that's right.

   glenn: In TTML we have the pixel aspect ratio (PAR), and the
   display aspect ratio DAR is the PAR * SAR where
   ... the SAR is the storage aspect ratio. So in TTML2 I
   introduced a number of new features:
   ... Some extensions to the extent value which can now take
   "cover" and "contain" which relate to the tts:extent;
   ... The tts:position attribute;
   ... The ttp:storageAspectRatio parameter.
   ... The intention of "contain" is to allow the root container
   region to be computed so that the display aspect
   ... ratio is preserved without extending outside of the extent
   of the media object.
   ... "cover" also maintains the aspect ratio but does so without
   any margin, in other words it can compute the
   ... extent so that the root extent can extend beyond the media
   object, without necessarily centering. It also
   ... preserves the display aspect ratio.
   ... The extent has the same DAR as in the document root
   container region and completely covers the media object.
   ... This isn't written in the spec yet - they're proposals from
   CSS. It may be that we don't need "cover". I
   ... included it for completeness. These are also useful for
   background image sizing.
   ... The second part of this is tts:position. I've defined that
   in TTML2 then if tts:position and tts:origin are present
   ... and a processor understands tts:position then tts:position
   takes precedence over tts:origin. The default
   ... for position is "center center".

   pal: So position is an enumeration?

   glenn: It is a complex expression that can have 1 to 4 terms
   two of which can be linked.

   tai: Position relates to the root container region?

   glenn: Look at the <position> definition. I defined it a bit
   more than CSS which is more prose-based.

   pal: Can I check what the use cases are for this level of
   flexibility? Aside from preserving aspect ratio.

   glenn: For example this simplifies the definition of regions.
   Let's say I want a 2 row region that is 1 row from
   ... the bottom of the screen regardless of the root container
   region, and I want it 80% of the width of the screen.
   ... What I can do is say tts:position="center bottom 10%"
   tts:extent="80% 20%" [draws picture]

   pal: So we couldn't just do that with origin 70%?

   glenn: It gets problematic when you want an offset but you're
   using extent="contains" for the root container region.

   pal: So in IMSC you could specify origin 70% down and height

   glenn: So that would yield the same percentage.

   pal: So if you don't specify an aspect ratio it would still be
   true regardless of being square or cinemascope.
   ... Now if I specify an aspect ratio say 4:3 in a 4:3 container
   it would still work. If I specify 16:9 in a 4:3 container
   ... then it would end up 10% up still. So I think I can achieve
   the same already. I'm trying to see what we're
   ... missing in IMSC 1.

   nigel: Can I throw in the definitions of vw and vh?

   glenn: A better example would have been not using %age but
   position="center bottom 10vh" and extent="80vw 20vh"
   ... because I neglected that percentage is computed in an
   unusual way in the position construct. It would align
   ... the 70% point in the container with the 70% point in the
   box being contained. This makes center=50%.

   nigel: There's now a picture of this in the section on





   glenn: You don't have to use the percentage system. You can use
   pixel or vh values, and they can be negative.

   nigel: The percentages can be negative too?

   glenn: Yes it looks that way. I just adopted this from CSS to
   support backgroundImage in the image element
   ... to have an adequate set of style properties and CSS has an
   image position property defined in these terms,
   ... which I thought we could reuse in this context.

   nigel: I'm not sure but I think this might make TTML <-->
   WebVTT mapping easier because I have the
   ... impression that WebVTT uses the same mechanism. Can anyone

   tai: I was thinking something similar, but it's a very
   different model from the current one, which may be a problem.
   ... From the usability perspective, the benefits of this are
   accompanied by additional complexity because it
   ... adds a new mechanism for something that is already present.

   glenn: The extent and origin model in TTML was good when you
   knew fixed pixel values and were not
   ... concerned with maintaining fixed aspect ratios. It began to
   get difficult when we added auto extent computation
   ... and the need for positions like "center". So we already had
   a problem to specify the IMSC 1 behaviour as
   ... written. It's easy in this model - you just say
   ... I've implemented this already and it wasn't complex.
   ... It was also more convenient authoring-wise rather than
   pre-computing values.

   nigel: You raised the question of if "cover" is needed. I think
   it may be needed because for non-full screen
   ... video the user research I've seen suggests that placing the
   subtitles beneath the video is preferred.

   pal: I think you need to make the distinction between the
   related media object and the viewport.

   nigel: That's right.

   glenn: I did mean to express whether the viewport is the
   related media object or the display. I think we need
   ... a way to define this.
   ... ttp:storageAspectRatio is a natural follow-on from

   pal: You have to define 2 out of the 3 to derive the third. I
   think defining DAR is better because it has more
   ... applicability and reduces the need for a calculation. This
   is supposed to be resolution independent.
   ... What about defining DAR and PAR but not SAR?

   glenn: The thing is we defined extent on tt as basically the
   SAR. It has to be defined in logical pixels with the
   ... PAR pixel sizes.

   nigel: So have we just defined SAR twice?

   glenn: We didn't use those words specifically but the extent is
   the equivalent of the SAR.
   ... It's true that the goal is to maintain DAR, and I could
   have picked DAR or SAR.
   ... We didn't mean SAR to be sample aspect ratio.
   ... In principle I don't see any reason off hand not to use DAR
   if that would be less confusing.

   pal: My argument is that if we're trying to get to DAR we
   should just specify it. And also say you can calculate
   ... storage aspect ratio by dividing DAR by PAR.

   glenn: The other thing I need to define for what a pixel means
   is the coordinate space. There are three that
   ... I've identified as relevant:
   ... 1. The document coordinate space;
   ... 2. The presentation context coordinate space;
   ... 3. The authoring context coordinate space (which may not be
   ... From the perspective of presentation the first two are
   needed. The presentation context coordinate space
   ... may or may not be the display (glass) pixel coordinate

   pal: So let's go to 'what is a pixel'. As soon as you define
   tts:extent in pixels then it's well defined. The
   ... definition of pixels is only an issue if you don't use
   ... If you define an extent in pixels e.g. 640x480, then
   whenever you use the measure pixels in the document
   ... you can always translate it to a percentage of the root
   container. We can always render it.

   glenn: For TTML1 unfortunately we adopted the XSL definition of
   pixel, but I don't think anyone took any notice
   ... of it, and everyone just interpreted it as you said, as a
   logical definition.

   pal: So I think we're trying to solve the case where there's a
   measure in pixels when tts:extent is not defined.
   ... I propose that we forbid the use of pixels when tts:extent
   is not defined.
   ... Or say if you do it then results are undefined.

   glenn: That's one option. I'm not sure if I'm ready to accept

   tai: I agree that it would be simpler to restrict something
   than to add something else. In the EBU group we
   ... spent 2-3 days discussing it and I'm not sure everyone had
   the same understanding at the end. We brought
   ... all these terms together.

   glenn: Even if you use cover or contain and you have a viewport
   that you can resolve then eventually all the
   ... coordinates end up in some space in that viewport.

   nigel: The question is do you need to?

   pal: The world is heading towards resolution independence.

   glenn: When I map TTML into SVG for example, SVG has a notion
   of a width and height on its root element and
   ... of its view box which defines a mapping between the extent
   of its coordinate space onto some other
   ... coordinate space. For example hxw = 100x100 and view box =
   200x300 and it would multiply the coordinates
   ... by 2 and 3 to get to the same coordinate space. I think we
   can define something similar in this case so that
   ... there is a definition of a coordinate but the resolution of
   that coordinate may depend on some external
   ... context.

   pal: I'm okay to allow it but have a weak definition and a hint
   or recommendation not to do it.

   glenn: I've got a couple of these coordinate space terms.
   ... The document coordinate space is only really used in extent
   and position. I haven't folded it in anywhere else.
   ... There's an issue to define pixels in a concrete way.

   nigel: As a devil's advocate straw man why do we not just say
   DAR is extent * pixelAspectRatio?

   pal: So if you specify extent and pixelAspectRatio then you'd
   better make sure they multiply to DAR.

   nigel: So we've created an over-constrained system by adding

   pal: In IMSC 1 tts:extent is not used to compute DAR. It's only
   used to define what the px measure means.

   nigel: We have a much bigger problem - tts:extent is defined in
   terms of <measure> which has been changed
   ... and can now have for example the value "available" - I
   don't know what that would mean here!

   glenn: The changes to <measure> were in response to Sean's
   shrink fitting proposal.
   ... I pulled them in from CSS.

   nigel: What does it mean if tts:extent uses those keywords in
   <measure> on the root element rather than
   ... scalar values?

   glenn: I was also trying to satisfy the sizing of images.

   nigel: It seems as though we need special care for the use of
   tts:extent on tt:tt, and many of the <measure>
   ... values don't have a clear meaning.
   ... Apologies I see that the wording "If tts:extent is
   specified on the tt element, then the width and height must be
   expressed in terms of two <length> specifications, and these
   specifications must be expressed as non-percentage, definite
   lengths using pixel units."
   ... is already present.
   ... I'm struggling to see how we have not therefore already
   defined display aspect ratio.

   glenn: That wording pasted above means that we can't specify
   "contain" and "cover".

   nigel: It seems to me that "contain" and "cover" on tt:tt are
   orthogonal to the pixel extent.

   glenn: They are.

   nigel: But we don't have a way to specify both. Maybe the way
   out here is to allow DAR to be specified if
   ... extent on tt is "cover" or "contain" but not otherwise.

   glenn and pal: discussion re the over-constraint of DAR, SAR
   and PAR if extent on root is in pixels and DAR is
   ... specified.

   pal: I'd prefer to deprecate PAR and be done with it, but we
   could mandate the behaviour in the specific case
   ... where all three are specified and don't agree.

   glenn: I'd rather put the wording in to define a single
   normative interpretation of the over-constrained but
   ... disagreeing scenario, so it's testable and consistent
   across implementations.

   nigel: Do we have an issue for this?

   glenn: The request is reasonable, to add DAR and remove SAR,
   but we don't have an issue for it.

   nigel: Okay let's create an issue.

   glenn: We already have issue-201

   issue-201: [TTWG meeting 2015-04-09] Agreed to remove
   ttp:storageAspectRatio, add a display aspect ratio parameter
   and deal with overconstrained inconsistent extent in pixels on
   root, DAR and PAR.

   <trackbot> Notes added to issue-201 How to specify aspect ratio
   to understand positioning that may apply for display or video..

ipd and bpd

   glenn: This came about from my interpretation of the SMPTE
   Digital Cinema requirement for inline space.

   pal: Yes, we wanted to be able to specify an inline space,
   positive or negative.

   glenn: So there's already a width and a height property in CSS
   that are used for the same purpose, but the
   ... problem with those is their names. They're interpreted in a
   writing mode relative way, so for vertical
   ... writing modes width means height and height means width. I
   wanted to avoid that conundrum because we
   ... use them in their absolute meanings throughout the
   document. In XSL-FO there's already the concept of
   ... the inline progression dimension and the block progression

   pal: So ipd allows a blank space to be defined in the inline

   glenn: No, it allows a size to be expressed, e.g. on a span, to
   define its size regardless of the content that it contains.

   Courtney: What does this do if you have vertical text?

   glenn: In vertical modes inline means vertical. bpd is the
   counterpart to that in the opposite axis, e.g. to allow
   ... a strut to be defined to separate lines by a specified

   pal: In TTML extent can only be applied to region...

   glenn: Right, if you put extent on a div say then it is
   shorthand for an inline region.

   pal: If you don't specify ipd on a div what's its computed

   glenn: It's equal to its containing block's ipd minus border
   and padding if they apply.

   pal: So it's a bit like padding for a content region by
   allowing them to be stretched until they reach that ipd?

   glenn: [draws on whiteboard] showing how a div will use all of
   the width of its parent's content rectangle
   ... after taking into account the border and padding.

   pal: That's all specified in CSS?

   glenn: Right, except they use the terms width and height. The
   height of a div will be the minimum needed to
   ... hold its content. It will shrink in the block progression
   dimension to be the minimum needed to hold its
   ... children. If you specify ipd and bpd explicitly instead of
   allowing your layout engine to calculate it then
   ... things change. If for example you specify an ipd that's
   less than what would normally be present then it would
   ... be constrained to be narrower than it would normally be
   (horizontal writing mode). If you make it wider
   ... then you have an overflow condition - I need to check CSS
   as it may constrain the maximum allowed width.
   ... The original reason to have an ipd was to allow spacing to
   be created without using space characters
   ... for example by creating a <span tts:ipd="5em"/>.

   tai: If you have a background color on all the spans the

   glenn: then you'd have <span tts:backgroundColor="red">A<span
   tts:ipd="5em"/>bad<span tts:ipd="5em"/>boy</span>
   ... for example. The background colour is drawn behind the
   extent even if it doesn't have any content in it.
   ... You could have <span tts:ipd="5em"
   ... That's how they came about. The request was just for ipd
   but I added bpd for symmetry.

   nigel: And last time we discussed this some folk were unhappy
   with the attribute names.
   ... I'm not sure if that's still true. How about an alternative
   like "inlineSize" and "blockSize"?
   ... The issue with the term 'dimension' is that it's used as a
   direction in some places in TTML.

   glenn: In XSL it's used as a size as distinct from inline
   progression direction.

   <glenn> ACTION: glenn to ensure consistency in TTML2 w.r.t.
   inline progression dimension vs direction [recorded in

   <trackbot> Created ACTION-384 - Ensure consistency in ttml2
   w.r.t. inline progression dimension vs direction [on Glenn
   Adams - due 2015-04-16].

   nigel: Will that resolve it for everyone?

   group: no objections to this approach, and keeping the names
   ipd and bpd.

Condition structure

   pal: I've not found a technical defect with this condition
   structure, but I think it's incredibly complex.
   ... It forces people to build a parser for the condition
   language. It's additive and people are already having
   ... trouble just rendering TTML. I think it adds a lot of
   complexity for what originally were a small set of use
   ... cases.

   glenn: There's a trade-off between expressiveness and
   complexity. If you look at e.g. media query, which people
   ... might quite likely want to conditionalise content based on,
   it often generates situations where you need
   ... at least logical expressions AND, OR, NOT etc and pretty
   soon want to compare parameters to others, like
   ... is width or height < or > some value, then you've got
   numerical comparisons as well as logical ones. Then
   ... soon you want arithmetic too! Just adding conditions that
   have named parameters and combinatorial logic
   ... for logical expressions doesn't seem very different to me
   than adding something that satisfies the more
   ... general case, and from a parsing perspective it's really
   straightforward. To write a parser for what is there
   ... now vs a subset is going to have almost the same
   complexity. The syntax now will require a lot of test content
   ... I didn't want to reinvent media queries. To implement the
   expression language I'd estimate as a day's work.

   nigel: You may want to conditionalise XML attributes on the
   tt:tt element but I can't see how you'd do that.
   ... For example you might want the extent to be dependent on
   whether the media is being viewed fullscreen
   ... or not fullscreen.

   glenn: There are limits to it. The precedent for this is the
   switch element in SMIL and SVG.
   ... What that system did was to limit the locations where
   switch is permitted, e.g. you can't use it to switch
   ... between definitions based on conditions. In TTML we have a
   number of definitional mechanisms like the
   ... region and style elements. So far I've permitted condition
   to be used on those, but the only one it can't
   ... apply to is the tt element itself. Is there any way to
   express the information on tt in a conditional way?
   ... I haven't thought about that.
   ... I did put condition on tt:tt but that may be overly

   nigel: You'd have to duplicate the whole tree.

   glenn: I'm not sure condition is going to work at all on the tt

   nigel: It's also unclear to me when the evaluation time is for
   conditions - is it any time during the presentation?

   glenn: My intention was to evaluate once before presentation
   and not again, but I guess implementations could
   ... offer on-the-go reevaluation. That could be implementation

   nigel: In terms of the spec it's not clear when the evaluation
   time should be.

   glenn: Certainly adding a note that needs to be defined would
   be prudent.

   nigel: You could also take an approach of using XML Query or
   other syntax and re-use existing techniques
   ... as a single evaluation before presentation.

   glenn: If you're suggesting throwing this out and using XML
   Query instead I think that would be overkill.
   ... I think what's in scope of our discussion is 'is there a
   testable implementable use case' that this meets, rather
   ... than complexity of implementation. Complexity is a profile
   issue. Let's say you want a profile that uses
   ... condition and limits the form of the expressions, such as
   'the only permitted functions are bound parameters'

   tai: I have recently been wondering if there will ever be a
   complete TTML implementation.
   ... You always need something like IMSC to be an implementable
   ... One proposal for this conditional mechanism: a complete
   example and use case in the spec would make it
   ... easier to understand.

   glenn: I agree it needs some examples.

   nigel: What's the list of use cases we have for this so far:
   forced display, ...?

   glenn: languages

   Courtney: I get asked for functionality to present translated
   subtitles as a licence requirement in some countries, tied to
   the audio language.
   ... e.g. if audio language == spanish then you must display
   subtitles in language XYZ. This is very similar
   ... to forced subtitles.

   tai: I thought of a use case that may or may not work, where
   you have a complete style set that is in use or
   ... out of use depending on the condition, to select predefined
   style sets.

   nigel: That could help meet the MAUR requirements

   pal: It wouldn't work for regulation.

   Courtney: full customisation at the terminal is a requirement
   for FCC

   pal: We don't need to put that functionality into TTML - it's a
   receiver thing only.

   nigel: Maybe it wouldn't work in the US but based on the
   feedback I see to BBC I think it would really be
   ... appreciated if broadcasters could offer different style
   sets, and not outrageous for broadcasters to provide
   ... them.

   tai: In Germany I can see that a useful option might be to put
   this in the document. We have discussions
   ... with TV manufacturers too and they don't see it as their
   business to provide configuration options.
   ... It's unclear how customisation works now - it has to be
   done by content provider apps.

   Courtney: Whatever layer is doing the rendering is where the
   options have to be evaluated.

   nigel: You could have some content provider provided
   transformations to allow for some styling.
   ... There's a problem with any kind of declarative styling
   which is that to style specific content you need to
   ... know how it's identified so that you can target (or select)
   it. Only the document author knows that, because
   ... it's document dependent.
   ... That makes customisation always difficult.

   Courtney: It could be interesting to investigate whether
   pre-defined transformations can meet all the user
   ... requirements for accessibility but there would be lots of
   work to do on it.

   glenn: We have to leave complexity until we've seen the
   implementations, unless someone can say what
   ... doesn't work about it.
   ... Obviously conditionalisation on the tt element is a
   limiting factor. Can we mitigate that and should we mitigate
   ... If the solution is very complex to specify and hard to
   understand then that could count against it.
   ... My main criteria are: is it specifiable, is it usable, is
   it implementable? Equally important.
   ... By the way we need to take out stereoLeft and stereoLeft.

   <scribe> ACTION: glenn remove stereoLeft and stereoRight from
   <bound-parameter> [recorded in

   <trackbot> Created ACTION-385 - Remove stereoleft and
   stereoright from <bound-parameter> [on Glenn Adams - due

   glenn: Are there any other bound parameters that folk want?

   nigel: You could add full-screen and then we can see how that
   plays out.
   ... The difference would be that for full-screen you want
   extent="contain" but if not then "cover" because
   ... there's more display to use.

   glenn: Let me think about that bigger level question there.
   I've already got a thought process in train for
   ... how to handle conditionalised parameters. In TTML2 we also
   allow all the style attributes to be added onto
   ... the tt:tt element and have them inherited by the region
   elements. They would maybe also need to be
   ... conditonal.

   nigel: But what's the difference between that and the initial

   glenn: I guess if you specified initial differently and did not
   specify them on a region then region would pick
   ... them up. Yes, maybe its redundant to put them on tt.

   <glenn> ACTION: glenn to investigate whether region style
   inheritance from tt is necessary given the ability to redefine
   initial values [recorded in

   <trackbot> Created ACTION-386 - Investigate whether region
   style inheritance from tt is necessary given the ability to
   redefine initial values [on Glenn Adams - due 2015-04-17].


   nigel: We've covered a lot today. Tomorrow we'll use the
   'spare' time available to go over the remaining
   ... TTML2 topics as well as everything else we have planned -
   let's prioritise based on time available and what
   ... everyone wants to do.
   ... We're restarting in the morning at 8:30.
   ... Thanks everynone! [adjourns meeting]

Summary of Action Items

   [NEW] ACTION: glenn remove stereoLeft and stereoRight from
   <bound-parameter> [recorded in
   [NEW] ACTION: glenn to ensure consistency in TTML2 w.r.t.
   inline progression dimension vs direction [recorded in
   [NEW] ACTION: glenn to investigate whether region style
   inheritance from tt is necessary given the ability to redefine
   initial values [recorded in

Summary of Resolutions

   [End of minutes]

    Minutes formatted by David Booth's [29]scribe.perl version
    1.143 ([30]CVS log)
    $Date: 2015/04/20 18:23:54 $

     [29] http://dev.w3.org/cvsweb/~checkout~/2002/scribe/scribedoc.htm

     [30] http://dev.w3.org/cvsweb/2002/scribe/

Day 2:


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

                               - DRAFT -

                Timed Text Working Group Teleconference

10 Apr 2015

   See also: [2]IRC log

      [2] http://www.w3.org/2015/04/10-tt-irc


          glenn, pal, tmichel, nigel, Courtney, tai, loretta





     * [3]Topics
         1. [4]Agenda today
         2. [5]IMSC 1 Test Suite and Implementations
         3. [6]IMSC 1 schedule and CR publication
         4. [7]Steps for exiting CR for IMSC 1
         5. [8]WebVTT FPWD Feedback handling
         6. [9]WebVTT <--> TTML Mapping
         7. [10]Actions
         8. [11]Issues
         9. [12]Sapporo TPAC F2F
        10. [13]TTML2 topics continued
        11. [14]Meeting ending!
     * [15]Summary of Action Items
     * [16]Summary of Resolutions

   <scribe> scribe: nigel

Agenda today

   nigel: Yesterday's minutes are visible at

   ... Last night during an out-of-meeting discussion some of us
   noticed that now that tts:bpd can make a content
   ... element taller than its contents maybe we need to permit
   displayAlign to define the relative alignment.

     [17] http://www.w3.org/2015/04/09-tt-minutes.html

   glenn: Yes, I've been thinking about that too. I'll create an
   issue for it.

   nigel: tts:ipd can apply to div, p and span but tts:textAlign
   only applies to p and span so maybe its needed there.

   glenn: I'll create an issue for that too.


   <trackbot> issue-384 -- tts:displayAlign may need to apply to
   content elements -- raised


     [18] http://www.w3.org/AudioVideo/TT/tracker/issues/384

   reopen issue-384

   <trackbot> Re-opened issue-384.


   <trackbot> issue-385 -- tts:textAlign may need to apply to div,
   body -- raised


     [19] http://www.w3.org/AudioVideo/TT/tracker/issues/385

   reopen issue-385

   <trackbot> Re-opened issue-385.

   nigel: My last thought on this one is that the empty spans with
   ipd and bpd shouldn't be pruned.
   ... This is related to issue-368


   <trackbot> issue-368 -- The [Construct Intermediate Document]
   process erroneously prunes empty <br> elements -- open


     [20] http://www.w3.org/AudioVideo/TT/tracker/issues/368

   issue-368: [Meeting 2015-04-10] Any empty content element that
   generates an area e.g. by setting ipd or bpd must not be pruned

   <trackbot> Notes added to issue-368 The [Construct Intermediate
   Document] process erroneously prunes empty <br> elements.

   nigel: As there are no more thoughts from yesterday, let's
   crack on with the planned agenda.

IMSC 1 Test Suite and Implementations




   pal: The test suite seems pretty stable. I know we've had some
   comments back that have been corrected.
   ... As far as I know its available for people to test. I was
   recently at an event where a couple of people
   ... tried to run the test suite for documents wrapped into MXF.
   I think people are trying it and experimenting.

   tai: Do they run the TTML tests too?

   pal: I don't know about that - but the maximum rate tests do
   exercise a lot of feature areas.
   ... I'm focusing on the IMSC 1 tests.
   ... I know that some folk have tried this but getting them to
   contribute their tests to W3C is a challenge.
   ... They're not quite sure how the work is going to be used.

   nigel: So maybe we need some better comms here to help people

   pal: A lot of implementors will not be W3C members because the
   web isn't their main business.
   ... So how do we manage this?

   nigel: Another data point here is an example I had recently - I
   was talking to someone whose dev team
   ... was in another part of the world and they didn't feel they
   could push that team to do extra work, but
   ... when they had delivered they would be able to try it. So
   maybe its lead time too.

   glenn: For TTML1 we had a template spreadsheet.

   tai: For manufacturers to proceed without guidance can be quite
   difficult. There may be a win win if
   ... we can also help them with their implementation work, in
   providing guidance, advice etc. on the spec.

   pal: Another obstacle that's related but different is that some
   manufacturers have as a policy non-disclosure
   ... of results until a spec is published, to avoid appearing to
   have non-compatibility with the spec until it has
   ... been formally finished.

   tmichel: You don't necessarily have to make public the
   implementor's name - they can be anonymised, as long
   ... as we know in the group which one is which.

   glenn: I heard you use the word "compatibility" which they
   don't have to claim, for our purposes.

   pal: That's a good point.
   ... W3C has implementation before standardisation - that's
   different from other groups where they
   ... standardise, implement and then fix the standard if needed.

   tai: We do see that in e.g. XML too where products area
   available before the spec is a recommendation.
   ... For commercial vendors if you give clear guidance and offer
   work together that would help.
   ... Another possibility is to see if there's an open source

   pal: That would be ideal.

   tai: In my experience with open source groups they are quite
   keen and do want real example content as
   ... well as test content.
   ... For presentation, that would be more a player like VLC for
   example. IRT has been in touch with them as
   ... part of the HBB4ALL group, and when we discussed with them
   the EBU-TT-D standard and the other related
   ... standards the VLC groups were quite interested in
   implementing when there is test content available.
   ... They gave me the impression they might implement based on
   examples rather than the spec.

   dakim: Caption vendors always ask for an xsd.

   pal: If you give them the maximum rate subtitle stuff, that has
   some useful coverage of styles, timing etc.

   nigel: Have we issued a formal invitation to provide

   tmichel: We did that formally when we published CR.

   nigel: Who saw that?

   tmichel: W3 groups, members. It was on the W3 home page.

   pal: A lot of the implementors won't have seen that.

   tmichel: If we know who we want to target I can help send the
   comms to them.

   glenn: It's best not to ask for general input.

   pal: I really like the idea of a form.

   nigel: Like a WBS form that's open to non-members?

   pal: Could be, or even a PDF form.

   nigel: I think there are two actions here: 1. Create the set of
   questions; 2. Collate the list of recipients.

   pal: I'd be happy to provide the list as I know it. I'd like
   some help with the form, since something similar
   ... has already been done.

   tai: What does this mean for the schedule?

   tmichel: I was proposing to start by contacting potential
   implementors by email, and then maybe invite
   ... them to attend a telecon. Another thing is to invite people
   as invited expert during the implementation
   ... period.

   nigel: I think that sounds a bit heavyweight - we don't need
   the invited expert bit IMO.

   tai: It's important not to make joining as an invited expert a
   requirement because the process isn't so easy, to join.

   pal: Does W3C have a presence at IBC?

   tai: EBU does.

   glenn: W3C has a presence at NAB.

   pal: That's a little soon, being tomorrow!

   tai: There may well be presentations at the IBC EBU booth - if
   you're there we can check with the EBU group and
   ... Frans if we can mention IMSC too. We get feedback that
   there's confusion about how all the different standards
   ... relate to each other.

   nigel: Sounds good to me (wearing my EBU group co-chair hat).

   <scribe> ACTION: pal Collate list of potential implementors of
   IMSC 1. [recorded in

   <trackbot> Created ACTION-387 - Collate list of potential
   implementors of imsc 1. [on Pierre-Anthony Lemieux - due

   <scribe> ACTION: tmichel Start preparing the IMSC 1
   Implementation report form. [recorded in

   <trackbot> Created ACTION-388 - Start preparing the imsc 1
   implementation report form. [on Thierry Michel - due

   <scribe> ACTION: tai Check with EBU group if we can have a
   combined event at IBC with EBU group and IMSC/W3C [recorded in

   <trackbot> Created ACTION-389 - Check with ebu group if we can
   have a combined event at ibc with ebu group and imsc/w3c [on
   Andreas Tai - due 2015-04-17].

   nigel: I found a couple of issues from a colleague who
   implemented the linePadding and multiRowAlign tests
   ... and from Andreas.
   ... 1. The example PNGs don't honour the displayAlign="center"
   setting (because I forgot that in the HTML)
   ... 2. The region doesn't begin 10% down
   ... 3. The text is so long that in real world implementations
   it doesn't necessarily fit on a line.
   ... I think we need to regenerate the PNGs to match the TTML,
   and also make the text shorter.

   <scribe> ACTION: nigel Update the multiRowAlign and linePadding
   TTML files to have shorter lines of text [recorded in

   <trackbot> Created ACTION-390 - Update the multirowalign and
   linepadding ttml files to have shorter lines of text [on Nigel
   Megitt - due 2015-04-17].

   <scribe> ACTION: nigel Update the multiRowAlign and linePadding
   PNGs to match the TTML [recorded in

   <trackbot> Created ACTION-391 - Update the multirowalign and
   linepadding pngs to match the ttml [on Nigel Megitt - due

   tai: I also noticed that the document order of the <p> elements
   is different from the display order of the regions
   ... So the first subtitle with the green background is rendered
   at the bottom and the second subtitle with
   ... the black background is rendered at the top. I think it
   would confuse people so I'd suggest to change that.
   ... It may just be a distraction.

   pal: I'll be happy to change that.

   nigel: This came from pal's original examples. I didn't change
   it because although it looks surprising it isn't
   ... wrong. I almost quite like it!

   Action-390: Also change the region ordering to be more

   <trackbot> Notes added to Action-390 Update the multirowalign
   and linepadding ttml files to have shorter lines of text.

   nigel: Some of the other example have it too, e.g.

   <scribe> ACTION: pal tweak the examples with multiple regions
   so that they appear in a more intuitive order. [recorded in

   <trackbot> Created ACTION-392 - Tweak the examples with
   multiple regions so that they appear in a more intuitive order.
   [on Pierre-Anthony Lemieux - due 2015-04-17].

   Action-392: (nigel will do the multiRowAlign and linePadding
   ones as per Action-390)

   <trackbot> Notes added to Action-392 Tweak the examples with
   multiple regions so that they appear in a more intuitive

   nigel: I'd like to show a prototype implementation that my
   colleagues at BBC R&D have put together based on
   ... gstreamer, using MPEG DASH to publish the content. I asked
   them to put the multiRowAlign and linePadding
   ... examples through it. They had to make a tweak because
   they're not actually valid EBU-TT-D as they use
   ... time expressions like "1s" where EBU-TT-D requires
   "hh:mm:ss.sss" type format.

   pal: Okay let's change that in the examples.

   Action-390: Change the time expressions to EBU-TT-D compliant
   ones too.

   <trackbot> Notes added to Action-390 Update the multirowalign
   and linepadding ttml files to have shorter lines of text.

   nigel: There are some tests that could be EBU-TT-D compatible
   too with these changes.

   Action-392: Also change the time expressions to be EBU-TT-D
   compliant on all that could be compliant

   <trackbot> Notes added to Action-392 Tweak the examples with
   multiple regions so that they appear in a more intuitive

   pal: Can we add this to the implementation report?

   nigel: Yes, as far as I'm concerned we can do that. Thierry is
   there any reason why not?

   tmichel: No reason why not. It would be good to post the videos

   nigel: They're large files, but otherwise no problem.

   tai: So for the BBC implementation they could just submit that
   they've passed those two tests?

   tmichel: Yes, that's fine. And it's okay to show even one test
   being passed by any implementation. Each
   ... test does need to have at least 2 implementations.

   tai: Is there any requirement to double check that the claims
   of passing the test are true?

   tmichel: We've relaxed this. Previously we would show the
   implementations working, but now it's based on
   ... trust. The only thing we should avoid is a misunderstanding
   of the output that you're supposed to get. You
   ... have to compare the output with some proof - it could be a
   video, a textual description, an image, or an SVG
   ... file etc.

   tai: Or it could be a member verification?

   pal: Yes, I was just asking nigel if BBC could submit this.

   tmichel: Each company should add their entry on the
   implementation report, using the form we're going to make.

   pal: There's space on the wiki so until we have the form we
   could just add a table to the results section
   ... on the implementation report, and then we can update when
   we have a fancier system.

   <scribe> ACTION: nigel Send pal details of implementation and
   tests passed so he can create a table in the implementation
   report [recorded in

   <trackbot> Created ACTION-393 - Send pal details of
   implementation and tests passed so he can create a table in the
   implementation report [on Nigel Megitt - due 2015-04-17].

   nigel: So we have a good news story - at least one
   implementation of two of the tests.

IMSC 1 schedule and CR publication

   pal: Let's look at today's schedule.


     [29] https://www.w3.org/wiki/TimedText/Publications

   pal: According to our schedule interop testing would have ended
   and we'd be publishing a CR2 around now.
   ... Interop testing is ongoing, and we have made some changes
   to the spec. Should we have a second CR?
   ... Should we proceed with that now, or wait for interop
   testing and feedback. Do we need a second CR at all?
   ... If we decide on a second CR we should maybe just do it
   according to our schedule.

   tmichel: I think it's better to publish a second CR now because
   there are no implementations yet and so its
   ... easier to justify the changes to the director. If you wait
   until PR then it's a tougher sell.

   pal: So maybe that answers that question!

   tmichel: The second issue is, if we publish a CR2, we might
   start thinking about at risk features if there are
   ... any, that we may want to remove to make going to PR easier.

   nigel: We currently have no at risk features marked.

   pal: That's right. The three that were in my mind most "at
   risk" due to implementations were multiRowAlign,
   ... linePadding and image. We've seen an implementation of
   multiRowAlign and linePadding this morning so
   ... they're not at risk, and I've seen plans for doing image
   already. So I don't believe there should be any at
   ... risk features.

   nigel: You've created the CR diff. Are there any open issues?

   pal: The only open issue is the one on begin, that we opened
   yesterday. Issue-382.
   ... Based on our discussion I think the answer is clear but I
   want to check on that some more.
   ... We also have issue-375.


   <trackbot> issue-375 -- Use of the ebutts:linePadding and
   ebutts:multiRowAlign in IMSC 1 -- pending review


     [30] http://www.w3.org/AudioVideo/TT/tracker/issues/375

   pal: In the CR it used to say "may be used" and now has "with
   the following provisions" and there's also the
   ... note added.

   tai: After we filed the first issue we found some additional
   points. Originally we wanted to allow the extension
   ... attributes to be permitted on the content elements, in
   contrast to EBU-TT-D that only allows them on style
   ... elements.
   ... There was a minor thing about the wording of the note to
   make clear that there is a difference between
   ... IMSC and EBU-TT-D and I proposed some wording that Pierre
   has added.
   ... I've read the updated text and am happy with it. There may
   be a small grammar issue - adding a 'the'.

   nigel: I've read it too.

   pal: I'm going to make that grammar change right now.

   dakim: What's the plan for referencing TTML2 from IMSC?

   pal: The plan is to make an IMSC 2 that references TTML2. Since
   both are similarly delayed it makes sense to
   ... stay with that plan. Let's discuss more after we're done
   with IMSC 1 here.
   ... I've pushed the grammar change now.

   close issue-375

   <trackbot> Closed issue-375.

   nigel: Great, now we have only one open issue.

   pal: So it sounds like the overhead for a second CR is low
   based on tmichel's input.

   tmichel: Yes, let's not say that these are substantial changes.

   pal: Yes. Some of them are normative provisions. Are they
   extensive or substantially affect the overall scope...

   glenn: Historically in this group our criteria has been: does
   it change the syntax in any way? If yes, it's substantive.
   ... If it significantly alters the compliance rules then we've
   also considered it substantive.

   nigel: What does that mean?

   glenn: There's some subjectivity in the word "significantly",
   which is a group choice.

   pal: So let's review the changes and determine that.

   glenn: We've also got some changes under the wire by saying
   that they fix a mistake, or haven't been implemented etc.





   pal: §6.6 Removal of frame rate relationship with related
   video object. One of the issues here is that you can't
   ... realistically test this without some video. In other words
   the impact is nil because we couldn't test this anyway.
   ... Any implementations that enforce the old language are still
   compliant. So the practical impact of this
   ... change is practically nil.

   tmichel: the exact wording in the W3C process defines
   substantive in

     [32] http://www.w3.org/2014/Process-20140801/#substantive-change

   glenn: In the past we have not considered the 3rd bullet in
   point 3 above to be substantive.

   tmichel: This is the new process though.

   pal: By the letter here any change that affects a normative
   provision falls into point 3.

   tai: What's the consequence if some changes are substantive?

   tmichel: In that case we need to have a director call.

   nigel: Even if we have some substantive changes I'm happy to
   take the Director through them.
   ... This specific change to §6.6 falls under the third bullet
   in point 3, so it does affect conformance;
   ... therefore under the new process it does count as
   ... The next one is in §6.7.1.

   pal: Again this is relaxing a constraint that used to bind a
   value in the TTML with an external object.
   ... The first change in this section is in the same category as
   the previous one we just discussed.

   nigel: Right, so this is classed as substantive.

   pal: The next one, removing the conformance regarding
   aspectRatio and extent is substantive for sure
   ... because it removes an enforceable check in the document.

   nigel: The third change in this section is the removal of a

   pal: That one is editorial by definition.

   nigel: The next change is in §7.4. This changes the initial
   value of tts:displayAlign.

   pal: That would affect presentation, i.e. processor behaviour.

   nigel: This is also classed as substantive.
   ... Next one is the same for textAlign.
   ... This is also classed as substantive.
   ... The next one is the set of changes to linePadding and

   pal: I think they have to be substantive because they clarify
   the situation relative to the previous version.

   nigel: Agreed.

   pal: I'd like the group believe that they are extensive enough
   to warrant doing wide review again for example.
   ... In my opinion the answer is no, but maybe we can have a
   group consensus to take to the Director.

   nigel: This is also classed as substantive.
   ... That was the last change.
   ... On the point about wide review, some of the changes are
   relative to SMPTE-TT so arguably we should
   ... give them the chance to respond.
   ... Just sending to SMPTE is narrow review though not wide
   ... My view is that this doesn't need wide review. One of the
   changes was in response to the previous
   ... wide review.

   pal: Yes, that arrived beyond the feedback deadline and we
   chose to defer knowing that we might have other
   ... changes.

   nigel: When we've completed the one remaining open action I'll
   raise a proposal in a future meeting to request
   ... transition to CR for the updated ED.

Steps for exiting CR for IMSC 1

   pal: Thierry, what are the steps for exiting, once we've
   published CR2?

   tmichel: First we have to publish CR2!
   ... We have to organise the request and the Director's call
   because there are substantive changes.

   pal: I will come back with a proposal for closing the last
   remaining issue.

   nigel: In the CR we have exit criteria, which are just about
   implementation. For CR2 we will need a new 'earliest
   ... date'?

   tmichel: Yes, at least 4 weeks beyond CR2 publication.

   nigel: So I think the steps are: 1) Complete the implementation
   report to meet the criteria, 2) request transition to PR.

   pal: And we have actions from earlier to help with 1.
   ... On the timeline, we will hopefully do CR2 in April, and
   probably not make PR in June. While that's going
   ... on we can start drafting IMSC 2.
   ... The only thing that will be tough is that SMPTE wanted IMSC
   1 to reach Rec in July so they can reference it.

   nigel: That's still possible.

   pal: True.

   nigel: If SMPTE has that goal and can encourage implementations
   then that will help them.

   pal: The plan for IMSC 2 is to base it on IMSC 1 and add any
   TTML 2 features such as Ruby or SMPTE requested
   ... features that people want.

   nigel: [5 minute break]

WebVTT FPWD Feedback handling

   Loretta: How do the CG and the WG work together?

   nigel: For Rec track stuff that has to come from the WG and
   feedback to go back to the WG.
   ... If there are any technical changes to the spec needed then
   it would be bad if the CG isn't happy with them.

   Courtney: It can be tricky to get consensus from the CG.

   tmichel: The WG has done a wide review. We received comments
   from i18n and CSS WG. We're expecting
   ... review from accessibility. That will close the debate on
   the wide review, as it will represent feedback from
   ... all the groups we have dependencies with.
   ... The only group missing is HTML and I'm expecting a
   statement that they're satisfied.

   nigel: I want to explore that some more - for IMSC 1 we took
   the view that wide review goes beyond just
   ... W3C group dependencies and to the wider world.

   tmichel: That's even better if we can demonstrate that review,
   but it's not essential.

   nigel: I was expecting more. For example to include the
   liaisons with external groups.

   tai: David Singer did post on the EBU group asking for wide
   review. That group hasn't provided any formal feedback.

   nigel: As a statement of fact, I don't believe there has been
   any feedback from any external group. I don't have
   ... visibility of any other requests David may have made.


     [33] http://www.w3.org/2014/Process-20140801/#doc-reviews

   nigel: We had a conversation by email about the process for
   responding and collecting wide review dispositions.



     [34] https://lists.w3.org/Archives/Public/public-tt/2015Apr/0006.html

   Loretta: who has the action to take that forward?

   tai: I think Dave offered to do it, on April 2.

   nigel: That email,

   .html says he doesn't
   ... see a problem with doing it, but that's not the same as
   taking the action, right?
   ... He offered to do bridging, and my follow-up was attempting
   to isolate where the bridging is needed.

     [35] https://lists.w3.org/Archives/Public/public-tt/2015Apr/0003.html

   Courtney: I think what he means is he's asked Silvia to do it.
   ... There's another email thread about CSS WG feedback, where a
   more concise version of it.
   ... We should have an ETA and know who is writing the
   dispositions document we discussed last week.

   Loretta: presumably the CG is blocking that?

   tmichel: The bridging also includes acceptance by this group of
   any proposals made by the CG.

   pal: In the case of IMSC 1 step 1 was to document every
   comment, which tmichel did. Then a proposed
   ... response was created and the commenter accepted or not and
   we discussed it. That's exactly what's
   ... required by the Director. The first step would be to
   document every comment received.

   tai: The working model between CG and WG is new as tmichel
   noted last week.

   nigel: I agree on both tai's and pal's points and don't think
   they're exclusive.

   pal: So the issues could be in the bug tracker.

   Loretta: Can we tag that they're comments so we can formally
   collate them?

   pal: There's also the recurring issue of IP - if the CG creates
   new IP in the course of responding to the comments,
   ... how do we ensure that the IP meets the requirements of W3C,
   in a continuous way?

   nigel: If there's a spec change made by a CG member who is not
   a WG member then the IP needs to be cleared
   ... on a case by case basis.

   Courtney: Is this only what's in the spec?

   tmichel: Only the spec changes need to be cleared.

   Courtney: If the IP question is based on versions of the

   pal: Then you might want to do another clearance call.

   tmichel: This is so complicated! I've been tracking people from
   the CG that have been active contributors and
   ... some never responded and are listed in the acknowledgement
   section as active contributors.

   Courtney: Part of the problem is that it's taken so long that
   people may have moved on.
   ... It sounds like we need to talk to Dave and maybe Silvia and
   get clarity on what everyone needs to be produced
   ... and a date for when it will be done and who is doing it.
   Let's get a schedule and then work to it.

   tmichel: Now it's in the tracker the CG should make proposals
   for the comment, as a first step IMO. The
   ... second step is for the TTWG to approve them.

   Courtney: We don't need to do that piecemeal for every comment.

   nigel: Part of the problem is we didn't set a review feedback
   end date on the FPWD of WebVTT so when do we stop?

   Courtney: We can get a specific date for accessibility review.

   tmichel: I'll do that.

   Courtney: Then we have to make a decision point - do we have
   wide review?

   nigel: We should check the process too on that. I have
   reservations on this. Let's review the process and charter.
   ... The process wants the charter's dependencies specifically
   to have been contacted. I don't think there's
   ... any archived evidence of Dave emailing them all, just the
   W3C groups in 3.1 of the charter. 3.2 and 3.3
   ... seem to be missing. The general public has been told, due
   to publication on the W3C homepage.
   ... In terms of appropriate times, the end date for feedback
   was not clear on the FPWD.
   ... One way to proceed here is to issue a second WD and a
   specific call for wide review with an end date
   ... and process any feedback from that, having solicited from
   all the dependencies on the charter.

   tmichel: That would be a good way to proceed.

   Courtney: I think that sounds like a good set of next steps for
   getting the wide review done. What's next after
   ... that?

   tmichel: Then we move to CR.

   nigel: Part of the CR is to specify exit criteria, which must
   include implementation experience.

   tmichel: In the pipe we also have issues regarding styling for
   example, such as inline or external stylesheets.
   ... Do we want to have those resolved in the current version or
   a later version?

   Courtney: IMO we should defer to a later version.

   Loretta: I would really like it in this version.

   Courtney: Then we have to get implementations. I see the value
   of having it in there but we don't have
   ... consensus on the design.

   Loretta: To my mind the conversation on this happens in the CG,
   and I think I saw a consensus emerging.

   Courtney: It's been quiet in the CG for the last 6 weeks.

   tmichel: Even if we went to CR for the current version I don't
   think there's evidence of implementation for
   ... the whole spec.

   Courtney: I don't agree. We've been supporting this in Apple
   since last fall in two separate implementations.
   ... In addition Google has an implementation.

   Loretta: It's not complete yet. The parsers and encoders
   support it, but Chrome does not. It doesn't do regions.
   ... What counts as an implementation?

   nigel: We can choose that in the CR exit criteria. We have some

   tmichel: We also need test suites. In my experience browser
   implementations don't implement a lot of features
   ... completely.

   tai: This is the same conversation as we had for IMSC, and we
   decided that we don't need single implementations
   ... that pass all the tests, just that every test is passed by
   at least two implementations.
   ... Silvia has started on the test suite in git.

   Courtney: We've been working on the tests too but don't have
   anything to share yet.
   ... So first we get evidence of wide review then we define the
   exit criteria, which could be passing tests in a
   ... test suite?

   nigel: Yes.

   Courtney: Going back to the inline styling question, because
   I'm interested in getting to a published version
   ... as soon as possible.

   nigel: Thinking about the existing CSSWG response, and other
   potential responses, in my opinion it's quite
   ... high risk to omit inline styling and require styling from a
   host HTML page.

   Loretta: I support the desire to get to Rec quickly.
   ... Previously the issue with inline styling was about syntax -
   the CG didn't agree it.

   Courtney: I think the action there is to contact David and
   Silvia and get a status on that.

   pal: Whatever decision they make, if there's a formal comment
   made then this group has to approve the response
   ... and the commenter's response to that may be positive or

   tai: So the WG has to approve the edit and that the comment has
   been addressed. Do we have the expertise
   ... on the spec to state that?

   nigel: My understanding is that we can't proceed without the
   expertise but that we have enough members
   ... from the CG like Silvia, Dave, Courtney, Loretta and Philip
   that we do have enough expertise.

   Courtney: So we have a 4 step process:
   ... 1. Get feedback.
   ... 2. Someone from the CG writes a proposed response.
   ... 3. The WG reviews the response and maybe edits.
   ... 4. Get the response form the original commenter.

   nigel: Step 2 is interesting - ideally I'd prefer for an
   individual who is a member of both the CG and WG and
   ... can be representative of the CG, so that at least we have
   some WG backing for the responses immediately.

   Courtney: I agree with that. I'm happy to talk to Dave about
   that - he may already have someone in mind to do that.

   nigel: I want to record the actions - can I just check it makes
   sense to put them in the WG tracker? They're
   ... WG actions.

   tai: Makes sense.

   Courtney: We're at a hand-over point between CG and WG.

   tmichel: Does it make sense to use the dispositions tracker for

   nigel: I would defer that until we know who is doing it.

   Loretta: have other groups used different tools?

   tmichel: You can do whatever you want. You can produce an Excel
   document or an HTML page that describes it
   ... You do need links to the archive for reference. The
   dispositions tool tracks the process steps.

   Loretta: In practice does everyone use it?

   tmichel: no.

   glenn: people use github and a variety of tools.

   nigel: Let's record the actions.

   <scribe> ACTION: Courtney Determine who is responsible for
   putting together the dispositions of comments document and get
   a schedule from them. [recorded in

   <trackbot> Created ACTION-394 - Determine who is responsible
   for putting together the dispositions of comments document and
   get a schedule from them. [on Courtney Kennedy - due

   <scribe> ACTION: tmichel Chase the accessibility WG for a date
   for getting WebVTT feedback [recorded in

   <trackbot> Created ACTION-395 - Chase the accessibility wg for
   a date for getting webvtt feedback [on Thierry Michel - due

   Courtney: if our response to comments is to change the spec do
   we have to redo the request for wide review?

   tmichel: If you publish a new WD then you only need to ask for
   comments on the delta.
   ... If we publish a new WD for wide review we should send an
   email to the groups on the charter and
   ... make sure it's archived. If Dave did that before then the
   emails are not on the archive.

   nigel: For IMSC 1 we sent to all the charter dependency groups
   and the W3C external liaisons filtered by
   ... interest area, BCCing the member-tt list so they were

   <scribe> ACTION: dsinger produce evidence of request for wide
   review for WebVTT, for the archive [recorded in

   <trackbot> Created ACTION-396 - Produce evidence of request for
   wide review for webvtt, for the archive [on David Singer - due

   nigel: So we're deferring the decision on a second WD dependent
   on the disposition of comments.
   ... Are the region semantics in WebVTT stable?

   Loretta: I think that's at risk. Philip doesn't like the way
   it's specced currently. AFAIK it's only implemented in
   ... Apple's players. It's not in Chrome, IE, Firefox or Opera.

   Courtney: Why is it at risk?

   nigel: I'm asking because I couldn't identify a resolution or
   consensus in the CG about the syntax and semantics.

   tmichel: The WG has published it so it is a consensus in that

   Loretta: If it's not implemented widely then that won't do us
   any favours.

   tmichel: What about the ::past and ::future pseudo-classes? I
   couldn't see support for that on any browser.

   tai: From reading the spec I'm unsure in general how much CSS
   feature support is required.

   nigel: While we're listing things we're curious about, what
   about the red box in §6.1 of the FPWD, which
   ... looks incomplete? We can't go to CR with that there, right?

   Courtney: It's not like that in the latest ED.

   nigel: In that case there have been changes.

   Loretta: There will be an action if we want to take a new
   snapshot. Someone needs to do a diff.

   nigel: That's an Editor's job.

   Loretta: Someone needs to understand what has changed in the ED
   to establish the diffs. The changes may
   ... be unrelated to comments.

   nigel: I've filed bug #28464
   [39]https://www.w3.org/Bugs/Public/show_bug.cgi?id=28464 for

     [39] https://www.w3.org/Bugs/Public/show_bug.cgi?id=28464

   tmichel: Does WebVTT do ruby support?

   Courtney: Yes it supports ruby but not to the extent that's in

   nigel: One of my key points is to make sure that there's
   alignment between new features in TTML and WebVTT.
   ... If the WebVTT Ruby implementation blocks future extension
   to get to the support level of TTML2 then
   ... we should file a bug.

   tmichel: Who decides?

   nigel: That's a WG decision.

   Courtney: We can use that as a criterion for evaluating new
   feature proposals.

   nigel: +1

   tmichel: Another thing that has been discussed is if the CSS
   feature list should be a whitelist or a blacklist.
   ... Dave, Nigel and I had different views of what the current
   wording means, and ought to mean.

   Courtney: Can CSS support profiles?

   glenn: No it does not, and there's no standard way to tell if a
   feature is implemented. There are some heuristics
   ... and javascript libraries like modernizr that can be used to
   mitigate those issues.
   ... One of the things I do is to set a value to something other
   than its initial value and then read its computed
   ... value. It's not a guarantee that the feature is
   implemented, but it's a good hint if you can't even get that

   nigel: Let's adjourn for lunch!

   group: Strong agreement!

WebVTT <--> TTML Mapping

   Courtney: We don't have too much to discuss with the group yet,
   but want to let you know about our plan.
   ... We discussed this in Geneva and I've been unable to make
   much progress since then. We want more
   ... structure around this so we can get it done. Andreas and I
   are working on a timeline and an outline for
   ... a document. We welcome help from anyone who wants to
   contribute text. Andreas and I will divide it up
   ... otherwise but if anyone else wants to help that would be

   nigel: What will that look like?

   Courtney: We haven't finalised anything. But let's think about
   the approach. Glenn brought this up in
   ... Geneva, that mapping from TTML to WebVTT directly isn't the
   way to go, instead to go from ISD to WebVTT.
   ... What we thought we could do is to map from IMSC to WebVTT.

   glenn: There is a spec for the ISD format in TTML2, but the
   mapping semantics need to be inferred from the
   ... rest of the spec but it's not perfect yet. A tool I've been
   working on, open source, based on TTX (TT transformer)
   ... will take an arbitrary TTML document and spit out a
   sequence of ISDs. So that's an examplar of what the
   ... semantics should be, but they're not written in detail in
   the spec.

   Courtney: If our goal was to write sample code we could use
   that but our task is to write a document.

   glenn: What that tool does is to flatten out the timeline and
   create a document for each interval during which
   ... no changes occur, and also flattens out the styles into the
   ISD documents. So a lot of the complexity in TTML
   ... disappears in that domain, and then it's easier to do a
   translation into some target format. If you don't do that
   ... but focus on IMSC you still have to deal with the
   complexity of the styling system.

   Courtney: Does IMSC require sequential timelines?

   pal: No, not unless you have progressivelyDecodable set.

   Courtney: My feeling is that its easier to start with a subset
   of TTML and then extend it later.

   tai: It makes sense to start with IMSC because it simplifies
   things, has a similar target usage, to WebVTT, and
   ... we might even start with a first draft based on something
   even more restricted to support the most
   ... commonly used features. Then we can add more as it is
   needed. From a formal perspective for an algorithm
   ... I think it may be the way to go to use ISDs, but it makes
   sense in the document to tackle certain features
   ... like position, timing, style, explain how it works in each
   spec, and then at least readers will understand the
   ... context and how it works. Even if any algorithm specified
   isn't used at least readers will be able to make
   ... their own. I think we made a good start in Geneva that is
   well minuted.
   ... Another thing we started is to work on the test files that
   we have that need to be built up for WebVTT. All
   ... these features can best be described using examples. The
   missing test files for WebVTT could also be
   ... generated.

   Courtney: I think we're going to do some more work on this next
   week (me and Andreas). In our conference
   ... call in 2 weeks we should have an outline and a schedule
   that we can share and discuss. We could circulate
   ... it on email too.

   nigel: It might make sense to use Mercurial to store it and
   allow it to be shared, or some other versioning tool.

   tai: That's publicly visible right?

   nigel: yes.

   Courtney: It would be good to have versioning.

   tai: I think it's important to do a first draft and then take
   it step by step.

   Courtney: I wanted to know if anyone wanted to contribute

   Loretta: Speak to me about this - I'll see what I can do.

   Courtney: It will also be good for developing the test suite.

   Loretta, tai, Courtney: discusses actual plans for getting
   together to work on this.

   nigel: Are there any particular inputs that you need e.g. in
   terms of expertise, understanding etc.

   Courtney: I think we may need to call on Glenn for TTML
   expertise and Silvia for WebVTT!

   glenn: One of these days someone will ask me to output WebVTT
   from my tool, and then I'll have to learn it!

   Courtney: Are you available to do that?

   glenn: Yes. The tool is all Java and is open source.
   ... There's another project called the TTV Timed Text
   Validator. TTX is the transformer layer on top of that.
   ... So this new timed text presentation engine is a layer on
   top of TTX, so it validates the TTML input,
   ... translates it into ISDs and then formats them.

   tai: Is there a place where we collate implementations?

   glenn: It would be a good idea to add that to the wiki.

   nigel: Sounds good to me.
   ... though we wouldn't necessarily endorse them.

   tai: It's good to let people know about this activity on the
   mappings in case people are also working on it.

   Loretta: Probably good to make some progress before raising
   expectations that we then discover we can't meet.

   nigel: Have you looked at the idea of picking the features that
   are easiest to match, even if they're from TTML2
   ... like the tts:position attribute?

   tai: I think we should start with TTML1 because it's more

   Courtney: We can certainly look at some low hanging fruit.

   nigel: An outcome of this work might be to identify subsets of
   the two specs that easily map to each other,
   ... and also any small additions to one spec or the other that
   would make the mapping much easier. We should
   ... capture those as outputs of the work if possible.

   tai: That would help with a more general desire to align the

   nigel: Knowing where the semantic overlap lies would be useful.

   glenn: Sure, where there are things like ruby, let's make sure
   they align semantically.

   nigel: I'm just saying if observations like that are made then
   we should capture them.

   tai: If there are possibilities of making mapping easier, like
   in TTML2 to map the semantics to CSS then in
   ... the long run that will make it easier.

   nigel: Looking at our charter, there are other documents that
   we could be working on, like the Note on live,
   ... and the mapping of 608/708 to WebVTT. Where's that last one
   up to?

   Courtney: Silvia wrote a second draft of that.

   nigel: Has Silvia done that in the CG - if it's in our charter
   I'd hope to publish it from here.

   Courtney: It's on the CG at the moment.




   nigel: I see there's quite a lot of work there - great!

   Courtney: Yes, and it's been updated recently.

   tai: She also proposed a mechanism for putting inline styles
   into VTT.

   Loretta: I don't think that's in the WebVTT spec yet. Certainly
   the original syntax for inline styles was never
   ... adopted into the VTT spec.

   tai: So a new proposal might overwrite this?

   Loretta: Sure if a new syntax is adopted then that document
   should be updated to include it.

   nigel: Thanks for making progress on the WebVTT TTML mapping
   document - it'll be good to make some
   ... progress there.
   ... Do you have a longer term schedule in mind?

   Courtney: We're hoping for something in time for the Sapporo
   face to face but it's too early to commit to a
   ... schedule until we've started working on it.

   tai: Also we might size the task to fit a particular timescale,
   at least for a first iteration.
   ... One last comment: is there an idea to have a common
   telephone conference where the WebVTT and TTML
   ... communities can come together? Would that be of use?

   Courtney: I think, speaking for myself, in the past it's been
   tough for Silvia because she's in Australia. So
   ... finding a good time could be difficult. A standing meeting
   might not have much support but we can
   ... schedule specific reviews as we need them.

   tai: That would be good to have.

   Loretta: We're ideally located to make finding meeting times
   maximally difficult!

   Courtney: Some working groups rotate it.

   pal: My suggestion is make sure there's a really clear agenda
   if you want people to get up in the middle of the night.

   nigel: Here in a meeting of 7 members and 1 observer,
   approximately half the members here today have an
   ... interest in WebVTT, so we're already doing it.

   Loretta: Of course not all the skills are here though!



   <trackbot> action-379 -- Nigel Megitt to Obtain png images for
   #linepadding and #multirowalign test cases. -- due 2015-03-19


     [41] http://www.w3.org/AudioVideo/TT/tracker/actions/379

   nigel: I did those PNGs but now they need fixing.
   ... But that's captured in Action-391, so I'll close this one.

   close action-379

   <trackbot> Closed action-379.


   <trackbot> action-381 -- Pierre-Anthony Lemieux to Prepare new
   list of changes to imsc 1 since cr1. -- due 2015-03-26 --


     [42] http://www.w3.org/AudioVideo/TT/tracker/actions/381

   pal: The next step is to close the outstanding issue and then
   prepare CR2.

   close action-381

   <trackbot> Closed action-381.

   nigel: I think we need a new date for the SOTD and a summary of
   differences since CR1.

   <scribe> ACTION: pal Prepare CR2 transition version (after
   closing one remaining issue on IMSC 1) [recorded in

   <trackbot> Created ACTION-397 - Prepare cr2 transition version
   (after closing one remaining issue on imsc 1) [on
   Pierre-Anthony Lemieux - due 2015-04-17].

   nigel: We also have two overdue actions, action-365 and
   action-378 which we can't complete either of yet.

   pal: That's right. Do we want to make the request to SMPTE as
   part of the wide review request on the next WD
   ... of TTML2?

   nigel: We could, I'm not sure. No particular reason to wait
   that I know of.

   pal: Okay, well that's ongoing.


   nigel: I don't believe we have any pending review issues - no
   we don't.


   <trackbot> issue-382 -- Require a computed non-indefinite begin
   time -- open


     [44] http://www.w3.org/AudioVideo/TT/tracker/issues/382

   pal: So just to confirm, if I list the TTML1 features, there's
   a #timing feature.

   glenn: That's a very generic feature.

   pal: Okay, so there's no granularity to build on.

   glenn: By the way the process for coming up with the features
   was subjective, and we used it to drive our
   ... tests. You're supposed to test features, but very few specs
   list features. So we took the approach of creating
   ... more fine grained features.

Sapporo TPAC F2F

   nigel: Looking at the survey results there's already enough
   backing for a meeting to say there's consensus
   ... to hold a meeting in Sapporo.
   ... There's a clear preference for the Monday and Tuesday and
   no objections to that, so it's clear that we
   ... should prefer those days.
   ... In terms of joint meetings, someone has suggested CSS-WG,
   and another suggestion is HTML WG.

   glenn: This is going to be difficult unless we make it short
   and extremely focused, like a single specific question
   ... to answer. Otherwise it will be a waste of time.

   nigel: My question is, what do people want to do there?

   glenn: Bert Bos has made comments on WebVTT. He might be
   interested in the line balancing algorithms.

   pal: I mistakenly hit the button for HTML WG and am going to
   unclick it.

   tai: We mentioned over lunch that working with HTML to
   understand how TTML TextTrackCues can work.

   glenn: We have a spec I wrote called the TTML API Level 1 and
   Level 2 (two specs) that try to define some
   ... things on top of the TextTrackCue interface that somewhat
   mirror the WebVTTCue. But there are lots of
   ... issues getting browser vendors to implement them. Microsoft
   and Opera might have an interest but
   ... Google, Apple and Mozilla don't seem to be interested. But
   my position is that it would be a pretty good
   ... way to go to use Javascript to populate a set of HTMLCues.
   Then you could transform into HTML on the
   ... server and feed it using Ajax and HXR to populate it, or
   have client side javascript that translates the TTML
   ... file locally, though that would probably be more
   complicated and less efficient than doing it on the server.
   ... That approach would allow either browser based HTML
   rendering or create a fragment containing SVG with
   ... a pre-rendered version of the cue. It turns out that inside
   the implementation in Webkit and Blink the
   ... same approach is used, to convert WebVTT to HTML and use

   pal: If this group has a consensus view that would be a good
   reason to meet with the HTML WG.

   glenn: The most likely answers are either 1) no or 2) write
   that as an extension spec and bring it to the HTML WG.
   ... There are various reasons for doing that - it's easier not
   to touch the HTML5 spec. Creating extensions is
   ... easier, so that's how I would approach it. If that's the
   likely response then we could organise our inputs to
   ... feed their expectations.

   pal: There'd be value in saying how to do it, though we don't
   have a volunteer for how to do that yet.

   glenn: The whole area of text cues in HTML5 is problematic in
   terms of testing and interoperability because
   ... they used a subjective process for getting to Rec. Those
   areas were marked as at risk during the CR process.
   ... Instead of addressing that they just published anyway.

   tai: But it's in the Rec?

   glenn: It is, so its final. The question is what comes next.
   The formal way that the HTML WG has decreed is that
   ... if you want to do something that doesn't fix 5.0 or add
   features for 6 then bring it as an extension.

   nigel: How does that approach interact with the WebVTT TTML
   mapping work?

   Loretta: It's orthogonal.

   glenn: +1
   ... You can say that the lack of a TTMLCue is a motivator for
   the mapping work, because you could use the
   ... mapping as a playback mechanism. I think its worth
   proposing a more generic cue proposal to the group
   ... at some point.

   nigel: That sounds like a great idea; so far we have nobody
   wanting to volunteer to work on that.
   ... Just to test the view of the group, do we have consensus
   that an HTMLCue would be a good way to do it?

   tai: +1

   pal: +1

   glenn: The good thing is that with a generic cue type then you
   can use any input format as long as you have
   ... javascript to create it. I already have a fairly complete
   proposal from Opera proposing a way to do this in
   ... blink.

   tai: But that's not public.

   glenn: Eric Lindstrom who was at our meeting in Geneva wrote

   pal: Could we bring that document to the group for review and
   take it to HTML WG?

   glenn: It's blink specific so it would need to be made more
   ... Maybe we could ask Eric if he wants to take this forward.

   tai: I can contact Eric if you give me an action.

   <scribe> ACTION: atai2 Contact Erik Lindstrom re HTMLCue
   [recorded in

   <trackbot> Created ACTION-398 - Contact erik lindstrom re
   htmlcue [on Andreas Tai - due 2015-04-17].

   glenn: Opera has membership of this group via Philip

   nigel: We do have consensus here that this is a good way to go,
   i.e. to propose to HTML WG HTMLCue as an extension
   ... That's everything from the survey results that I need for
   my response to the organisers. That doesn't
   ... close the survey - any new or amended responses will still
   be taken into account.
   ... But it does mean we will go ahead with a Monday and Tuesday
   ... Is there anything that we want to cover in that meeting?

   tai: We should reserve some time for the mapping, regardless of
   what state we're in.

   pal: Hopefully we'll be done with IMSC 1 but if not we should
   address any blockers. We should also work on
   ... a 1st draft of IMSC 2, that should exist at that time. The
   hope is that IMSC 2 is simpler as a document
   ... than IMSC 1 because all the features will be a subset of

   glenn: You will probably want an informative section mapping
   IMSC 1 features into IMSC 2 if they're no longer
   ... present in IMSC 2. I imagine you might want to say
   something about migration, continuing use of old content etc.

   nigel: For TTML2 maybe we should be targeting implementation

   glenn: I definitely hope we'll be in CR by then.

   pal: When will you be able to show implementations of your

   glenn: The TTPE presentation tool I've been writing should be
   available at end of June. Probably end of August
   ... to finalise the arabic, hebrew and bidi additions to it.

   pal: That will remove a huge risk to TTML2.

   glenn: I'm hoping to be able to get a lot of the new features
   into it as well. So we can have at least one
   ... system to pass tests. I'm also adding support to the TTML
   Validator to validate the new constructs.
   ... So in a sense we could point to the Validator as one
   implementation and the presentation engine as the
   ... other implementation even though one is built on the other.

   nigel: There is a question the Director will ask about who
   wrote the implementations. In this case we could have
   ... an answer which is that the spec and both implementations
   were written by the same individual. I don't think
   ... that he'd be that happy with that!

   tai: A quick question about what TTPE does: from the
   documentation I'm not clear what the outputs are?

   glenn: [draws on the whiteboard] There are 3 layers: TTV, TTX
   and TTPE. Generic TTML files can feed into
   ... TTV - TTML1 or TTML2. It validates every feature of TTML1
   and Iâm enhancing it as I go to support TTML2
   ... features. TTX converts into ISDs in a sequence which
   consists of multiple instances of an ISD.
   ... TTPE then does two things: layout and then rendering. It
   takes the ISDs and creates an area tree which
   ... is very similar to what's in XSL-FO, or a box tree in CSS
   terms. It has things like block areas, line areas,
   ... glyph areas, space areas that fill the lines up. The
   rendering process then turns that into the chosen output
   ... format (specified on the command line) - one of XML for
   debug, SVG or PNG. I've also specced out renderers
   ... for html and vtt that I and the other engineers working on
   this haven't built yet. They just take the area
   ... tree as the input and then write out whatever is needed to
   create the same visual output as is specified.
   ... It's very easy for SVG. TTV and TTX are both in the TTV
   project in github. TTPE is a separate project.

   pal: When that implementation is available, that removes a huge
   risk for TTML2 because there's at least one
   ... baseline implementation for features. So it's hard for me
   to imagine not being able to enter CR in August.

   Loretta: It looks like there's a lot of input for the TTML to
   WebVTT mapping there.

   glenn: The question is how to map from the area tree to WebVTT.
   It's hard to work out how to do the positioning in WebVTT.
   ... Since WebVTT doesn't have pixel positioning I may have to
   use the regions feature to do the layout.
   ... One of the things about the mapping is that you can lose
   information without losing everything. At the basic
   ... level I could pull the text out of the area tree and blast
   it into a WebVTT cue. That would lose a lot of information!
   ... It's a question how to include positioning properly.

   Courtney: Another item for the F2F in Sapporo should be the
   WebVTT progress.

   dakim: Do you think the ruby stuff is important for WebVTT v1?

   Courtney: I think it's less important than inline styling, and
   also we need to figure out how to do it in terms
   ... of the design. A lot of what we need is already in CSS so
   maybe if you do inline styling in CSS maybe you
   ... get all the ruby functionality you need.

   dakim: I've got a bug open with Philip that you can't annotate
   the rt tag.

   Courtney: If that's a minor change to the spec then we could
   consider adding that. I want to balance the features
   ... against getting to a spec as quickly as possible.

   nigel: Obviously that's a consensus issue for the group.

   Loretta: the call is when it's needed not whether it's needed.

TTML2 topics continued

   pal: I'd like to ask about ttp:contentProfiles "any"
   ... I'd like to walk through the positioning of images in TTML2

   dakim: I'm wondering why people would use extent and origin on
   content elements to define inline regions instead of just ipd
   and bpd

   nigel: For ttp:contentProfiles what sense does "any" make?

   glenn: I see what you mean - I can't see why an author would
   claim conformance with at least one of but not
   ... all of a set of content profiles.


   <trackbot> issue-386 -- There's no apparent use case for the
   "any" term in ttp:contentProfiles -- raised


     [46] http://www.w3.org/AudioVideo/TT/tracker/issues/386

   reopen issue-386

   <trackbot> Re-opened issue-386.

   nigel: The next point was also raised by pal: the positioning
   of images in TTML2

   pal: How do you position images?

   glenn: If it's a background image then use the background
   position properties. If it's a non-background image
   ... then you can treat it like a block or inline area so the
   rules apply, like ipd and bpd. Extent and origin do
   ... not apply to content elements - they create regions.
   ... There are two ways to do it - you can put a background
   image on a region. That's intended to support
   ... non-content images. For content images e.g. with rasterised
   text in them one should not use the
   ... backgroundImage mechanism but instead use image like in
   html. Put it in a block context e.g. as a child
   ... of a div or in a p. So if you put a span with an ipd and
   bpd then it's now an inline block with an image in it.
   ... If you want to do fine positioning you have to use spans
   with ipd and bpd.

   pal: So if I wanted an image 80% from the top and 20% from the
   left of the viewport.

   glenn: I'd create a region and define its position using the
   position attribute or origin. Then I'd put a div in it
   ... with a single image inside that div. That would be the
   easiest way to position it.
   ... If that's the only content in the region it would position
   it. You can also use ipd and bpd.

   nigel: Have we got scaling semantics for images if we use ipd
   and bpd?

   glenn: I thought so - I don't believe there's an issue.


   <trackbot> issue-387 -- Consider applying ipd or bpd to content
   images -- raised


     [47] http://www.w3.org/AudioVideo/TT/tracker/issues/387

   reopen issue-387

   <trackbot> Re-opened issue-387.

   pal: When I read the document the simple option wasn't obvious.

   glenn: By the way displayAlign and textAlign would apply to it.
   ... I think you may also be permitted to put an image in a body
   without a div.
   ... No, body has to have div in it, div can have embedded class
   like image or other divs or ps.

   nigel: The last point to raise is that content elements can
   have style attributes extent, position, origin, ipd and bpd all
   ... simultaneously. I think the semantics are clear but some
   readers of the documents will find it hard to
   ... understand. It may be useful to add non-normative examples
   or text to explain this scenario.

   glenn: That's a feature of languages as they get bigger. I have
   an issue already to add recommendation text
   ... to say that style attributes should not be put on content
   elements where they do not apply and can not be
   ... inherited from.

   nigel: It might also be useful to include an example document
   or non-normative text somewhere to remove
   ... or reduce the likelihood of confusion there.
   ... The last question I have is where we're up to on the CSS
   semantics mappings?

   glenn: I have a proposal out for mapping to html that will
   generate that, but I don't have the resource to do that
   ... at the moment.

   tai: Didn't you have some draft material for that?

   glenn: jdsmith picked up some work from Sean re change proposal
   5 but that needs further attention.


     [48] https://www.w3.org/wiki/TTML/changeProposal005

   glenn: When we started this work there was an idea that someone
   could create a Javascript shim that would
   ... generate HTML/CSS.
   ... CP5 needs to be carefully reviewed because the time
   evaluation algorithm wouldn't work. It also attempts
   ... to specify some algorithms on how to resolve styles. We
   already have some normative language on
   ... style resolution in the spec. My plan was to take that
   information and also timing rules and wrote them
   ... into the spec in a readable fashion in the context of an
   ISD sequence then it would eliminate talking about
   ... style and timing resolution in the context of an HTML

   nigel: I was expecting equivalence notes under the style
   attributes to say what the equivalent CSS semantics
   ... are to the already stated XSL semantics. I think CP5 is
   something different and much more complex.

   glenn: I'm not sure how useful that would be.

   nigel: I think it would be extremely useful.

   glenn: In § and §, when we originally talked
   about a CSS mapping the intent was to define
   ... two subsections of § one based on XSL-FO and the
   other on CSS. That means taking part of the
   ... material from CP5 and formally doing it in a way that is
   congruous with the XSL-FO.

   tai: I understood this activity to be as Glenn described, but
   even just additional notes as nigel described would
   ... have a big impact on readability, especially if the CSS
   semantic is first.

   glenn: I'd be happy to put the CSS equivalents first.

   tai: People don't know how close the features already are to
   CSS so it would make the document much more
   ... accessible.

   glenn: It would be insufficient just to create an equivalence
   table for each style attribute. We'd also have to do an
   ... algorithm in §

   nigel: I agree with that.

   glenn: Nobody has been pushing me to do this much!
   ... I won't be confident about the algorithm until I've seen it
   in code though. I'd be happy to use CP5
   ... as a starting point at least though.

   nigel: I think that's all on this and everything I had on the
   queue to deal with. In terms of your spreadsheet
   ... glenn did you have any remaining technical questions?

   glenn: I don't think so - I have a pretty good idea on most of
   the remaining things and I will come to the group
   ... if there are any other questions. For example on disparity
   if there's anything unclear in the issue.
   ... I'd like a response from SMPTE to know that they'll be
   satisfied with what we've proposed.

   nigel: pal has the action to draft that. Good to know that
   there's a pressing need for that.

   glenn: I'd like to draft some of the members to do some work
   particularly on the examples and images of
   ... examples.
   ... I have about 25 entries that have to do with creating
   example source content or images or both. I could do
   ... it but my time would be better spent creating technical
   solutions. There's also an annex Q about a CEA708
   ... mapping that it would be useful to have someone look at.

   pal: Just point to RP2052-11 which already does it.

   glenn: Does that point to SMPTE additions to TTML?

   pal: I doubt it - it doesn't use image. I'm just offering an
   easy way to do that.

   glenn: I don't know if that's going to be sufficient - it needs
   to be reviewed.

   pal: I don't think we need that section - if nobody volunteers
   to write it we can remove it.

   glenn: We've added 6 metadata items preceded with cea708 and
   others preceded cea608. I have a note to
   ... elaborate those with reference to 608 and 708. If someone
   could sign up for doing some of the related
   ... work items that would be useful.
   ... In the end with TTML1 where we did this everyone had a role
   bringing some spec text in.

   nigel: Okay, I appreciate the request and think that's a really
   good idea. It's not necessarily a good moment
   ... to start assigning tasks now, but let's think about that
   and how to take it forward.

   glenn: I reserve the right to ensure consistency of language
   and edit contributions.

   nigel: Okay, we have the spreadsheet available (see yesterday's
   minutes) - everyone have a look at that and if
   ... you want to contribute something contact me or glenn and
   let's share out those tasks.

   glenn: nigel you raised issues on appendix L.

   nigel: I've done the work to guess the new values for the
   conformance column against requirements - it's in the issue.

   glenn: In Appendix M the element derivation needs to be updated
   for the new properties.
   ... It would be useful to have a list of elements and
   attributes to add or change on the tables in M.
   ... By the way you could edit the source document itself if
   you're set up to run ant, and I could help you set
   ... up your build environment so you can run the authoring
   tools. We have an old process for generating the
   ... spec using an XSLT-based translation process with a DTD.
   The language we write the spec in is governed by
   ... XMLSpec that came out of the XML WG.
   ... There's a stylesheet too.

   nigel: Okay, that's interesting - let me know if you're
   interested in setting that up.

Meeting ending!

   nigel: Thanks to netflix for sponsoring this meeting, and to
   Glenn for buying lunch.

   glenn: And thanks to Netflix for sponsoring that lunch.

   nigel: I think we've had a really productive two days, so
   thanks everyone for attending and contributing.

   tai: And thanks for chairing and scribing too!

   nigel: Thanks!
   ... We've done all our goals for this meeting and also handled
   issues or at least come up with action plans.
   ... So well done everyone!
   ... [adjourns meeting]

Summary of Action Items

   [NEW] ACTION: atai2 Contact Erik Lindstrom re HTMLCue [recorded
   in [49]http://www.w3.org/2015/04/10-tt-minutes.html#action12]
   [NEW] ACTION: Courtney Determine who is responsible for putting
   together the dispositions of comments document and get a
   schedule from them. [recorded in
   [NEW] ACTION: dsinger produce evidence of request for wide
   review for WebVTT, for the archive [recorded in
   [NEW] ACTION: nigel Send pal details of implementation and
   tests passed so he can create a table in the implementation
   report [recorded in
   [NEW] ACTION: nigel Update the multiRowAlign and linePadding
   PNGs to match the TTML [recorded in
   [NEW] ACTION: nigel Update the multiRowAlign and linePadding
   TTML files to have shorter lines of text [recorded in
   [NEW] ACTION: pal Collate list of potential implementors of
   IMSC 1. [recorded in
   [NEW] ACTION: pal Prepare CR2 transition version (after closing
   one remaining issue on IMSC 1) [recorded in
   [NEW] ACTION: pal tweak the examples with multiple regions so
   that they appear in a more intuitive order. [recorded in
   [NEW] ACTION: tai Check with EBU group if we can have a
   combined event at IBC with EBU group and IMSC/W3C [recorded in
   [NEW] ACTION: tmichel Chase the accessibility WG for a date for
   getting WebVTT feedback [recorded in
   [NEW] ACTION: tmichel Start preparing the IMSC 1 Implementation
   report form. [recorded in

Summary of Resolutions

   [End of minutes]

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    $Date: 2015/04/20 18:24:09 $

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Received on Wednesday, 22 April 2015 12:28:29 UTC

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