- From: Nigel Megitt <nigel.megitt@bbc.co.uk>
- Date: Thu, 25 Jun 2020 16:49:24 +0000
- To: W3C Public TTWG <public-tt@w3.org>
- Message-ID: <1A1EC7D1-BD1C-4F7C-A0FE-76C7608BBD27@bbc.co.uk>
Thanks all for attending today's TTWG meeting. Minutes can be found in HTML format at https://www.w3.org/2020/06/25-tt-minutes.html
In text format:
[1]W3C
[1] https://www.w3.org/
Timed Text Working Group Teleconference
25 June 2020
[2]Previous meeting. [3]Agenda. [4]IRC log.
[2] https://www.w3.org/2020/06/18-tt-minutes.html
[3] https://github.com/w3c/ttwg/issues/123
[4] https://www.w3.org/2020/06/25-tt-irc
Attendees
Present
Andreas, Atsushi, Cyril, Gary, Nigel, Pierre
Regrets
-
Chair
Gary, Nigel
Scribe
nigel
Contents
1. [5]This meeting
2. [6]IMSC 1.2 PR changes
3. [7][WR/ARIB] Compatibility with ARIB-TTML / 5. Additional
style control imsc#550
4. [8]Incoming liaison from ARIB re IMSC 1.2 ttwg#116
5. [9]CSS font-matching algorithm may introduce fingerprinting
issues w3c/ttml2#1202 (PING review)
6. [10]AOB: TTML Profile Registry
7. [11]Virtual TPAC
8. [12]Meeting close
Meeting minutes
This meeting
Nigel: I hope we can finish off on the ARIB topics so we can
start preparing a response.
… Then there's TTML2 2nd Ed IR as a placeholder, and the PING
review on font-matching
… which I have something to report on, and is worth us
discussing.
… AOB?
group: [no other business]
Nigel: One from me - the TTML Profile Registry needs a small
amount of love
IMSC 1.2 PR changes
Nigel: Reminder re last week's agenda and minutes
Pierre: I've been waiting before processing them - I could do
them as they come in, either way.
Nigel: I suspect there won't be any other changes, so we can go
ahead.
Pierre: Okay, will do.
[WR/ARIB] Compatibility with ARIB-TTML / 5. Additional style control
imsc#550
github: [13]https://github.com/w3c/imsc/issues/550
[13] https://github.com/w3c/imsc/issues/550
Pierre: Can we come back to the character space question?
… If I'm not mistaken ARIB-TT letter spacing is to control the
space between individual
… letters, positive and negative. The TTML2 feature
tts:letterSpacing is intended to be applied
… to a sequence of characters to grow or shrink the space
between characters overall, rather
… than between individual characters. For that there is
tts:ipd, but that does not support
… negative values.
… We should confirm that ARIB's use of letter spacing is for
individual character pairs.
Nigel: Is there anything to stop you using TTML2
tts:letterSpacing and putting 2 characters
… in it though?
Pierre: Imagine you have 3 characters and you want to change
the spacing between each of
… the two pairs. You can't do that with tts:letterSpacing.
Nigel: This is bringing back nasty memories
Pierre: I'm fairly certain we concluded that we could not
support controlling negative
… spacing between pairs of letters independently.
… The reason I remember this is that the request came from
Digital Cinema originally
… where there is something like IPD that supports negative
values. I think that may have
… been introduced specifically to support the Japanese market.
Cyril: If you're nesting spans and changing the letterSpacing
at each span level would it
… disallow you from controlling the spacing between each pair?
Pierre: Right, but in a long sentence you end up with a
terrible hierarchical structure.
Cyril: I know!
Nigel: I don't remember the answer but I remember asking if
letterSpacing applies to the
… distance between the last character of the previous span and
the first character of the
… span with letterSpacing set, or conversely at the end.
Pierre: I'm still struggling to understand why the right
solution is not to handle bespoke
… spacing in the font itself.
Nigel: It's orthogonal though, you might want to change the
letter spacing for one instance
… of a word only, e.g. the word WAVE in the TTML2 example. You
can still do it on the font as well, for all uses.
Pierre: That would be the perfect use case, for artistic
purposes, where there is an exceptional
… reason, negative IPD could be really helpful. But the reality
might be that people would
… use it between every character, which is what I've seen in
digital cinema, which defeats
… the purpose entirely, in my mind.
Nigel: [wonders aloud about ipd or letterSpacing on empty
spans]
Pierre: ipd is really simple, that's done I think.
Cyril: What happens if you set an ipd that is smaller than the
calculated ipd? Does it limit
… the dimension?
Pierre: Say that again?
Cyril: Say you have a span, and you want to reduce the advance
on the last character.
… You add tts:ipd to that span whose value is less than the sum
of the advances of all the
… characters in that span.
Pierre: That depends on the font, right?
Cyril: Sure, yes.
… And if you combine letterSpacing and ipd?
Pierre: This might be a really good discussion to have with
ARIB, if they're willing to have a
… technical discussion.
Nigel: Let's log that and see if we can look at the other
attributes.
… They are border, marquee, ruby and text-shadow.
… We have some of these.
… We certainly have textShadow, but I haven't had chance to
check if it is the same.
… OK looking in the English translation, the ARIB version has
offset-x, offset-y, blur-radius and color.
… Checking TTML2, it is exactly the same.
Pierre: Good news, I guess.
Nigel: I think so.
… OK let's look at the next one...
… marquee is probably easy: I don't think we have that in
TTML2. It does what you would think,
… specifying text scrolling.
… I recall Glenn wondering if there was some use case for
animation where the same
… effect could be synthesised but I don't think he ever
demonstrated it.
… I see we have w3c/ttml3#2
Pierre: It would be good to see what effect they are looking
for.
Nigel: Agreed, and also to get some usage data.
… There are two more: border and ruby
… Looking at border.
… In ARIB, it is < border-style>, <border-width> and
<border-color>
… There are lots of styles, including double, groove, ridge,
inset, outset, dashed, dotted, none and hidden.
… In TTML2 we have none, dotted, dashed, solid and double.
… So for this one it looks like there may be a couple of styles
they have defined, but the
… overall syntax and semantics are similar. TTML2 has a
border-radius which ARIB does not
… have.
… Let's look at ruby:
… The ARIB ruby attribute is an xml:id of the content which is
subject to the ruby being
… defined, presumably in a span with the ruby attribute.
… This is a simpler model than in TTML2, but does not describe
alignment, position or reserved space.
Pierre: I'm fairly confident that TTML2 does a really good job
with ruby, modulo the hanging
… issues, the complex ones. Overall I think there should be no
deltas there.
Nigel: There are deltas, both in syntax and in functionality,
but on this one TTML2 has more functionality.
Pierre: I would think that TTML2 is a superset.
Nigel: The one thing we don't have is infinite levels of
nesting of ruby, in TTML2.
… ARIB's solution does support that.
Pierre: I think there's an issue for that. We might want to ask
if nested rubys are useful
… in subtitles and captions.
Nigel: Yes.
… I think we've iterated through all the ARIB attributes now.
… For this issue, I think we can describe the overlaps and gaps
in functionality but really
… what we're interested in asking ARIB is about the usage.
Pierre: Yes
SUMMARY: There are some overlaps and some gaps between the
ARIB-TT styling attributes and those in TTML2. We are
interested to know more about the usage, especially where there
are gaps in TTML2.
Incoming liaison from ARIB re IMSC 1.2 ttwg#116
github: [14]https://github.com/w3c/ttwg/issues/116
[14] https://github.com/w3c/ttwg/issues/116
Nigel: We have now concluded our run-through of all the points
made in the ARIB liaison,
… and I think I have the action now to collate the conclusions
from our discussions into
… proposed feedback to ARIB.
Pierre: Sounds great.
Atsushi: Great
Nigel: Okay, thank you, I'll pick that up.
SUMMARY: @nigelmegitt to collate discussions and questions and
propose a draft liaison message in response to ARIB.
CSS font-matching algorithm may introduce fingerprinting issues
w3c/ttml2#1202 (PING review)
github: [15]https://github.com/w3c/ttml2/issues/1202
[15] https://github.com/w3c/ttml2/issues/1202
Nigel: Some activity to report:
… 1. Sam got back to me earlier today or late yesterday
proposing times for a joint meeting.
… 2. Andreas proposed an alternative, stronger-sounding
wording, which Glenn thought
… could work modulo a couple of editorial tweaks.
… Sam proposed 1:45pm Eastern. That's a little late for me, he
suggested the earliest
… possible time would be 1:30pm Eastern, but next week might
work too.
… For a half hour call.
… I will respond to explore the options for a suitable time.
Possibly it will be next week.
… I will propose a doodle, since several people may want to
attend.
… Hopefully this will allow us to understand each others'
objectives and constraints and
… work towards a consensus solution.
… Thank you Andreas for your proposals too. They look good to
me also.
Andreas: No response to my comments, other than from Glenn.
Nigel: Good, let's hope that we have a path out of this.
SUMMARY: @nigelmegitt to respond to Sam regarding a joint
meeting, to try to arrange it.
AOB: TTML Profile Registry
Nigel: Sorry to nag on this (I did that by email too), but
[16]https://github.com/w3c/tt-profile-registry/pull/73
… is open and has been for over a month, to add a new short
code.
… If someone could please review and approve, that would be v
helpful.
… I am conscious that the Editor is not very active in the
group at the moment, so I am
… tempted to assign another Editor. I can do it myself but I
still need review input.
[16] https://github.com/w3c/tt-profile-registry/pull/73
Cyril: I can do the review.
Pierre: I'm happy to help. Recommend letting Mike and Glenn
know.
Nigel: Yes, absolutely.
Cyril: I've approved it, it's straightforward. It has all the
required elements for a registry change.
Nigel: Thank you.
… I also opened [17]https://github.com/w3c/tt-profile-registry/
issues/74 to add IMSC 1.2
… profiles as well.
… Can anyone see a reason not to add the IMSC 1.2 profiles now?
[17] https://github.com/w3c/tt-profile-registry/issues/74
Cyril: No, we don't expect IMSC 1.2 not to be published!
Nigel: No we don't.
Cyril: We just have to invent a new 4cc.
Nigel: There's a pattern, it's straightforward.
… Shall I go ahead and propose a pull request?
Cyril: Yes please go ahead.
Nigel: It's going to be im3t. And im3i? We haven't changed
anything in the image profile!
Cyril: If we have a new namespace we should have a new
identifier.
Pierre: Exactly, and we don't for Image.
Cyril: So it's just im3t then.
Nigel: Okay, that's clear, thank you.
… Just add im3i.
… But should we add IMSC 1.2 to the public specification list
for im2i?
Cyril: We could have two values in the public specification
section for im2i?
Nigel: Yes
Cyril: Why not?
Pierre: Yes, it can't hurt.
… The best way to be completely unambiguous is if we match each
of the 4ccs to a profile designator.
Cyril: It's already the case.
Pierre: Oh then just add a second reference.
Nigel: Perfect, I think that gives me everything I need to
know.
<atsushi> AOB+ W3C team is keen to support the Group moving
forward. And TPAC meeting this year is going virtual, some of
you already put comments, but we are interested in hearing from
you on how it can go (if you have any further
comment/suggestion).
Virtual TPAC
Atsushi: TPAC this year will be virtual, and W3 Team is keen to
get all comments and
… suggestions on the new virtual TPAC then they will be
appreciated.
… Not to worry if you don't have anything.
Pierre: I've sent comments to Philippe as requested.
… I let him know that one of the most important aspects could
be joint meetings.
… He also mentioned something that was not immediately obvious
to me, that might
… be of interest to the group. When I asked what the value of
the group meetings at TPAC
… since the groups can have meetings at any time, he pointed
out that at TPAC it is a good
… opportunity for guests to attend and observe.
… So we may still think it is useful to schedule an hour long
meeting to invite guests to
… attend. I don't think we should do 4 or 8 hours, but to
discuss where the group is up to
… would be useful.
… Also the opportunity for a joint meeting with CSS would be
really good. We should have
… that at least once a year.
Gary: The Media WG is planning to hold regular meetings unless
there are scheduled
… joint meetings during TPAC. They're not planning for a
regular TPAC style schedule.
Nigel: CSS reminds me there are some features we want that
probably nobody is implementing.
… If we want them then we should probably implement them!
Pierre: Yes, the poster-child for this is shear. As I
understand it there is a strong difference
… of opinion on even if shear should be permitted. It would be
good to make progress on
… that if we can. As far as I can tell it is a W3C internal
issue, getting the various groups
… to come to a resolution on this.
Atsushi: For that specific point, I think some discussion with
the EPUB3 WG would be helpful.
Pierre: Should we organise that for TPAC, or a different time?
I think nothing will happen
… in CSS unless we solve that specific issue.
Atsushi: I think talking with Koji Ishii separately might be
better.
Pierre: How can I help? The issue is well documented inside and
outside W3C.
Atsushi: There is a complex situation. Traditionally there was
no shear in Japanese typography
… and recently some are using it. For horizontal at least it is
natural to follow how US-ASCII
… or some other European characters are transformed, but there
is no standard way for
… vertical layout. Within the publishing community, there is
some mutual understanding of
… how it should be done, which side of Japanese characters
should shear.
… It was not common in Japanese typography so there was no
requirement in JIS standards.
… If we want to put this in CSS we may need to push information
into CSS WG from the
… digital publication side instead of traditional Japanese
typography.
Pierre: Yes, and that has been done. But the situation is that
it is used every day for
… subtitles in theaters. Not being permitted in print should
not mean it is not permitted
… in subtitles, since it is in use today.
Atsushi: My understanding is there is no standard way to shear.
Pierre: In cinema there is a standard way.
… A Japanese specialist has provided this in the JLReq repo,
but that has been ignored
… so far, which is unfortunate.
Atsushi: I will contact Koji Ishii about this.
… I had several comments from Japanese web designers that the
implementation of shearing
… for vertical text differs between browser implementations. So
many web designers are
… using images for these kinds of cases.
… There is a need from web designers also. I will write an
email to him.
Nigel: Conscious of time, we're 10 minutes over, if we need
proper agenda time for this
… please add it to next week's agenda.
Meeting close
Nigel: Thank you very much everyone, see you next week.
[adjourns meeting]
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Received on Thursday, 25 June 2020 16:49:41 UTC