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: 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: 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: 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 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.
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 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?
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]