IRC log of tt on 2020-05-28

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Meeting: Timed Text Working Group Teleconference
15:01:00 [nigel]
scribe: nigel
15:01:03 [nigel]
Agenda: https://github.com/w3c/ttwg/issues/117
15:01:12 [nigel]
Previous meeting: https://www.w3.org/2020/05/21-tt-minutes.html
15:01:20 [atsushi]
present+
15:01:25 [nigel]
Present: Vladimir, Nigel, Atsushi
15:01:48 [nigel]
Chair: Nigel
15:02:04 [nigel]
Present+ Pierre
15:02:43 [nigel]
Present+ Andreas
15:03:03 [nigel]
Present+ Gary
15:04:07 [Vladimir]
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15:04:17 [Vladimir]
present+
15:04:27 [nigel]
Topic: This meeting
15:05:03 [nigel]
Nigel: Today we have some IMSC topics: PR transition, vNext requirements window,
15:05:27 [nigel]
.. and ARIB issues. We also have a placeholder for TTML2 IR but I don't think there's
15:05:29 [nigel]
.. much to discuss there.
15:05:43 [nigel]
.. AOB or points to remind the Chair to make sure get covered?
15:06:14 [nigel]
Pierre: Admin: can we talk about the pull requests that are updating links on the published Rec.?
15:06:28 [nigel]
.. They say the PR is not for release. Can we take 5 minutes on this.
15:06:29 [cyril]
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Nigel: Right, on IMSC?
15:06:42 [nigel]
Pierre: Yes, old IMSC, 1.0.1, 1.1
15:06:48 [nigel]
Present+ Cyril
15:07:23 [nigel]
Topic: IMSC 1.2 CfC to request transition to PR
15:07:33 [nigel]
Nigel: Reminder that the CfC is open until 5th June.
15:07:46 [nigel]
-> https://lists.w3.org/Archives/Public/public-tt/2020May/0033.html CfC to request transition of IMSC 1.2 to PR
15:08:04 [nigel]
-> https://github.com/w3c/transitions/issues/245 Draft transition request
15:08:17 [nigel]
Nigel: Anything to raise on this topic?
15:08:41 [nigel]
Topic: IMSC vNext requirements window
15:08:59 [nigel]
Nigel: 2 current drivers for this (so far):
15:09:15 [nigel]
.. 1. Netflix requirements provided by Cyril a few weeks back
15:09:19 [nigel]
.. 2. ARIB liaison
15:09:25 [nigel]
.. Of course there may be other requirements.
15:09:43 [nigel]
.. Historically we have opened a window for people to register new requirements,
15:09:54 [atai]
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15:09:55 [nigel]
.. and I propose doing the same thing again. The question is the time window for
15:09:58 [nigel]
.. doing this.
15:10:05 [nigel]
.. Any proposals?
15:10:42 [nigel]
Pierre: It would help if we as a community try to guess what the scope would be.
15:10:50 [nigel]
.. It's hard before calling for requirements, but it would help on the timing.
15:11:01 [nigel]
.. We have contributions from Disney and Netflix that are very specific.
15:11:13 [nigel]
.. We have ARIB which are very specific too and potentially the changes will be more significant.
15:11:17 [nigel]
.. Do we foresee anything else?
15:11:33 [nigel]
Nigel: I don't think I'm aware of any right now.
15:12:26 [nigel]
.. Something else that's relevant is that CSS is working on Ruby stuff at the moment
15:12:34 [nigel]
.. so we potentially have a sync point with their work.
15:12:43 [atsushi]
(sorry for delay of my email on these, Nigel)
15:13:31 [nigel]
.. It feels that there may be a need to get agreement with multiple parties who might
15:13:36 [nigel]
.. take a while to respond.
15:13:41 [nigel]
Pierre: That's my feeling too.
15:13:54 [nigel]
.. We could adopt a new more flexible process where we could issue regular snapshots
15:14:06 [nigel]
.. and address issues as they come up, and decide to go to Rec or not Rec based on
15:14:11 [nigel]
.. how much we have.
15:14:28 [nigel]
.. If we do the traditional process for Rec like we did with IMSC 1.2 then it will be many months.
15:14:45 [nigel]
.. Question for Netflix is how urgent the fontShear work is for Rec publication.
15:14:57 [nigel]
Cyril: Good question, I would say the sooner the better because I want to avoid divergence
15:15:03 [nigel]
.. between actual implementation and content deployed.
15:15:14 [nigel]
.. But alignment with CSS is important, at the same time.
15:15:36 [nigel]
Pierre: Thinking out loud, a more iterative process is not incompatible with the idea of
15:15:45 [nigel]
.. a requirements window for establishing the scope of what we are doing.
15:15:50 [nigel]
.. We could freeze them now!
15:15:51 [atsushi]
q+ just a comment on font shear in Japanese
15:16:03 [nigel]
Nigel: Not sure that's wise!
15:16:15 [nigel]
Pierre: I'm saying a short period, give people 2 months rather than 6.
15:16:19 [nigel]
ack ats
15:16:39 [nigel]
Atsushi: Comment on font shear. In i18n JLREQ task force we discussed font shear in
15:16:57 [nigel]
.. Japanese. But our knowledge was that font shear is not used in Japanese typography
15:17:08 [nigel]
.. so the TF decided not to state any requirement for font shear in JLREQ.
15:17:29 [nigel]
.. There is a common way to share font in Japanese typography used for publishing,
15:17:41 [nigel]
.. but we haven't had mutual agreement to state something to CSS WG yet. Just for information.
15:18:13 [nigel]
Cyril: That's interesting because it is exactly the opposite of the conversation I had with
15:18:29 [nigel]
.. the CSS WG member from Google who is from Japan. Koji Ishi maybe. The way we want
15:18:42 [nigel]
.. to do shearing in general is exactly the way it is done in Japanese typography so we
15:18:45 [nigel]
.. probably need to resolve that.
15:18:59 [nigel]
Atsushi: I think he mentioned the common way that font shear is done in recent Japanese
15:19:12 [nigel]
.. books. For input to CSS WG we may need to state something from some sort of
15:19:26 [nigel]
.. Japanese group. We failed to get to agreement in the JLREQ TF. To have some statement
15:19:44 [nigel]
.. we have to get input from a digital publishing group in Japan. I think I need to go back
15:19:56 [nigel]
.. to W3C Keio with this to complete the coordination.
15:20:39 [nigel]
Nigel: Another question about a requirements gathering phase is how we make it known
15:20:57 [nigel]
.. to the world. For example liaisons, as we have done previously, or a W3 blog post etc
15:21:08 [nigel]
.. It seems that some folk have come to us without any need for this.
15:22:10 [nigel]
.. Can we say now that the requirements window is open, and think about the closing date
15:22:18 [nigel]
.. and comms for it in the next few days?
15:23:01 [nigel]
PROPOSAL: The window for new requirements for future versions of IMSC after 1.2 is now open.
15:23:10 [nigel]
Nigel: Any objections?
15:23:18 [atsushi]
+1
15:23:21 [nigel]
Cyril: no
15:23:24 [nigel]
Pierre: Sounds good to me
15:23:27 [nigel]
RESOLUTION: The window for new requirements for future versions of IMSC after 1.2 is now open.
15:23:41 [atsushi]
(+1 means go ahead w/ no objection)
15:23:42 [nigel]
Nigel: Thank you.
15:24:52 [nigel]
Topic: [WR/ARIB] Mixture of text and image w3c/imsc#543
15:24:57 [nigel]
github: https://github.com/w3c/imsc/issues/543
15:26:22 [nigel]
Vladimir: Just for clarification, can we clarify exactly what they mean by inline graphics?
15:26:26 [nigel]
.. I'm not sure what they really mean.
15:27:37 [nigel]
Nigel: I understand it to be the kind of requirement where a company logo is inserted as
15:27:41 [nigel]
.. a graphic inline with text.
15:27:54 [nigel]
Vladimir: If someone wants to use a PUA code point in a user defined font for this, then
15:28:10 [nigel]
.. there is nothing we can do to stop them. I would say that would be a pretty unobjectionable
15:28:23 [nigel]
.. use of PUA codes because that's exactly what they're for. It's not going to hinder text
15:28:34 [cyril]
this IMSC requirement has an example https://github.com/w3c/tt-reqs/issues/15
15:28:40 [nigel]
.. processing or editing or search. I think that is not really a concern.
15:28:41 [nigel]
q+
15:29:00 [nigel]
.. My concern was about GSUB substitution when you need to select the right form.
15:29:14 [nigel]
.. Anything that would be used to avoid doing standard processing for truly text content.
15:29:27 [nigel]
.. If they want to simplify things by missing some functionality I would say that's a bad idea.
15:30:33 [cyril]
q+
15:30:43 [nigel]
.. They say that if GSUB is used before IVS is used then, it sounds like they want to simplify
15:30:56 [nigel]
.. by avoiding the need to do it. I think they just want to use PUA to see something they
15:31:07 [nigel]
.. want to be displayed. I would say that is a bad idea. It might work in a closed system
15:31:19 [nigel]
.. where the Timed Text is authored in the same environment but as soon as you attempt
15:31:33 [nigel]
.. to make it something more interoperable then you can't expect everyone to do it the same way.
15:32:01 [nigel]
Nigel: I wanted to note that PUA use can impact text processing, for example if a company
15:32:15 [nigel]
.. name is being substituted for its logo, then you might reasonably want to do things like
15:32:23 [nigel]
.. Text to Speech of the text,
15:32:29 [nigel]
.. Searching by text name,
15:32:42 [nigel]
.. all before any substitution. If PUA is used that really will break those use cases.
15:33:31 [nigel]
.. I think that is why we got to the point of using GSUB as a good idea before.
15:33:45 [nigel]
Vladimir: I absolutely agree with this. I don't think that PUA should be used in place of
15:33:52 [nigel]
.. a company name, because the implementation will break.
15:34:03 [nigel]
q+ Pierre
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pal has joined #tt
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ack n
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Cyril: I agree with what Vlad said. I talked to my Netflix experts and they are of the same
15:34:37 [nigel]
.. opinion that we should avoid PUA as much as possible for all the reasons that were
15:34:49 [nigel]
.. explained. I am wondering how ARIB got the notion that we require GSUB, because I
15:34:59 [nigel]
.. don't think it is mentioned in the spec. Secondly maybe we should add something but
15:35:11 [nigel]
s/but
15:35:25 [nigel]
.. to limit the complexity of the implementation. I don't know if we can, for example limit
15:35:41 [Vladimir]
q+
15:35:42 [nigel]
.. the font functionality required for IMSC. Are there profiles for this? I don't know.
15:35:52 [nigel]
ack v
15:36:05 [nigel]
Vladimir: Any attempt to do something to simplify implementation to let them off the hook
15:36:18 [nigel]
.. of a specific standardised feature, I think is not a good idea, because that feature may
15:36:26 [nigel]
.. manifest itself elsewhere that we cannot predict.
15:36:46 [nigel]
.. If normal text comes in and implementations drop a standardised case then
15:36:56 [nigel]
.. preprocessing would be needed. The short answer: I don't think it's a good idea to
15:37:06 [nigel]
.. simplify implementations if it goes against the standardised feature set.
15:37:12 [nigel]
ack Pier
15:37:25 [nigel]
Pierre: I think what we should do is get actual samples. It just occurred to me that there
15:37:36 [nigel]
.. are no examples of what they are trying to do. We should try to see how this works
15:37:48 [nigel]
.. in practice. We had a long thread on what we wanted to do with GSUB and we should
15:37:56 [nigel]
.. try it and assess how well supported and how easy it is.
15:38:09 [nigel]
.. We're at the point where we need to try it before we come up with a solution.
15:38:20 [nigel]
.. I would actually go back to ARIB and request a sample.
15:38:28 [nigel]
Nigel: That's a really good idea
15:38:40 [nigel]
Cyril: Are there tools that allow us to easily create fonts with a GSUB substitution?
15:38:59 [nigel]
Vladimir: Any font tool - most of them allow substitutions. You write your own rules as
15:39:13 [nigel]
.. a code entry, to substitute a sequence of glyphs. You don't know what those glyphs
15:39:36 [nigel]
.. represent. You just set a rule. Any sequence of input can be substituted. For example
15:39:44 [nigel]
.. a company name substituted by a logo is perfectly possible.
15:40:03 [nigel]
.. For example the Zapfino font, on most Macs I think, has a substitution entry that
15:40:16 [nigel]
.. substitutes the name of the font for the ligature. They do it just to showcase it.
15:40:26 [nigel]
.. You can substitute a ligature or anything else.
15:40:46 [nigel]
Nigel: That's an input sequence of code points?
15:40:55 [nigel]
Vladimir: The input is a sequence of unicode text points.
15:41:14 [nigel]
.. Then map those to glyph ids.
15:41:23 [nigel]
.. Then most of the time the substitution rules apply to those glyph ids
15:41:35 [nigel]
.. Then you have character codes, and depending on location and many other rules, the
15:41:42 [nigel]
.. base glyph can be substituted by something else.
15:41:59 [nigel]
.. For example in Arabic, a positional variant; for Japanese, a variation sequence definition.
15:42:17 [nigel]
.. If you have a ligature for example for a sequence of glyphs, that is applied to the glyph
15:42:22 [atai]
q+
15:42:25 [nigel]
.. id sequence mapped from the character codes.
15:42:47 [nigel]
.. You end up as part of this process as one code point entry mapped to a glyph that is
15:42:54 [pal]
q-
15:42:55 [nigel]
.. one of a number of possibilities.
15:42:58 [nigel]
ack c
15:43:00 [nigel]
ack at
15:43:14 [nigel]
Andreas: A question re GSUB and PUA. Regarding the concerns that Nigel mentioned
15:43:26 [nigel]
.. for example using text for a screen reader, where is the difference between GSUB and
15:43:33 [nigel]
.. the use of PUAs? Both are not very accessible.
15:43:50 [nigel]
Vladimir: It's exactly opposite. Your accessibility is defined by the code point sequence.
15:44:02 [nigel]
.. Then your Unicode sequence does not change and is used by the screen reader.
15:44:15 [nigel]
.. The font level modifications will only affect visible display, not the content itself.
15:44:24 [nigel]
.. That is why this is probably the only accessible way of doing things.
15:44:25 [atai]
q+
15:44:47 [nigel]
.. If you move visualisation decisions upstream and simply use a PUA code point to map
15:45:00 [nigel]
.. to a particular glyph, then you break accessibility, because now your screen reader has
15:45:04 [nigel]
.. no idea what that is.
15:45:05 [nigel]
ack at
15:45:19 [nigel]
Andreas: And there is no requirement that the mapping of the glyphs that people will read
15:45:29 [nigel]
.. will go with what is specified by the code points.
15:45:43 [nigel]
Vladimir: Exactly, which is why PUA should be avoided unless there is something that has
15:45:51 [nigel]
.. no meaning for somebody who cannot see the text.
15:46:05 [cyril]
Zapfino example: data:text/html,<div%20style="font:%2048px%20Zapfino">Zapfino<br>Zapfin%20o
15:46:16 [nigel]
.. If you have "company name, logo" where logo is a PUA then that's fine if the screen reader
15:46:28 [nigel]
.. ignores the PUA but if the company name is omitted then it will not be accessible.
15:47:05 [nigel]
Nigel: This reminds me of presentation-scheme based fallback options, and I think we
15:47:12 [nigel]
.. should avoid those if we possibly can.
15:47:33 [nigel]
Vladimir: Yes exactly, and that is the basis of the Unicode choice to let font engines
15:47:46 [nigel]
.. do substitutions where needed so that they only affect visual presentation.
15:47:57 [nigel]
Cyril: I asked my font expert if there is a limit to the length of the substitution, and he
15:48:05 [nigel]
.. told me it can be very long, like 30 glyphs. Is there a limit?
15:48:13 [nigel]
Vladimir: I don't think so, only practical limitations.
15:48:27 [nigel]
.. Substitution tables can define a chain of substitutions and it is only limited by
15:48:34 [nigel]
.. complexity and how far a font designer wants to go.
15:48:42 [nigel]
q?
15:49:00 [nigel]
Cyril: Vladimir you were asking for an example. Earlier on IRC I posted a link to one of the
15:49:13 [nigel]
.. requirements that we have. Nigel showed an example of the Twitter logo inline with the
15:49:15 [nigel]
.. text.
15:49:19 [nigel]
Nigel: Thanks for digging that out!
15:49:29 [nigel]
Cyril: It's w3c/tt-reqs#15
15:49:37 [nigel]
Pierre: That's the issue that led to the current situation in IMSC and TTML.
15:49:50 [nigel]
.. It would be good to get input from ARIB with sample text and corresponding render.
15:50:05 [nigel]
Vladimir: Yes, for example if someone wants to define the logo as a PUA code in additoin
15:50:14 [nigel]
.. to the name Twitter, then that would be fine.
15:50:28 [nigel]
.. But if you drop the name and only use the PUA for the logo, it breaks accessibility.
15:50:41 [nigel]
.. Better to do it as a font substitution, for visual presentation.
15:50:52 [nigel]
.. As far as content sequences are concerned the name Twitter is still there.
15:51:06 [nigel]
Cyril: Also graceful degradation, in case the font engine doesn't support substitution.
15:51:19 [nigel]
Vladimir: I agree. Any time substitution fails you see the original unsubstituted text.
15:51:53 [nigel]
.. For company names that's fine. For Devanagari almost everything is a substitution, so
15:51:56 [nigel]
.. the presentation would fail.
15:52:13 [nigel]
Cyril: I'm trying to get back to the ARIB issue and understand what exactly they wanted.
15:52:29 [nigel]
.. They end by saying to consider that PUA is a simple implementation and a clear indication
15:52:36 [nigel]
.. on the use of GSUB would be helpful.
15:52:50 [nigel]
.. On the first point I think we disagree with them. We don't want to recommend it.
15:53:02 [nigel]
Pierre: I can't even conclude that without seeing what they want to do and making sure
15:53:05 [nigel]
.. that we can do it.
15:53:07 [Vladimir]
q+
15:53:20 [nigel]
Cyril: I agree that would be useful. I wonder if we should say that PUA is not recommended.
15:53:38 [nigel]
Pierre: Imagine they come back with a PUA example where we can't give a better alternative.
15:53:57 [nigel]
Cyril: You would want to say at this stage we cannot ...
15:54:03 [nigel]
Pierre: I would like to get a solid example.
15:54:10 [nigel]
Cyril: Yes, okay that's good.
15:54:19 [nigel]
Pierre: If they cannot produce an example that also informs us a lot.
15:54:37 [nigel]
Vladimir: 2 final comments. One on what was just discussed. I don't think we can do anything
15:54:49 [nigel]
.. to stop them using PUA codes. If someone decides to use it we cannot prevent it.
15:55:16 [nigel]
.. On the substitution side, trying to define something in the TTML spec, all we can say
15:55:27 [nigel]
.. is we expect font engines to be conformant with the OFF standard.
15:55:41 [nigel]
.. If they support the standard then that's not a concern.
15:55:52 [nigel]
Cyril: I don't think we want to explain how substitution works in general, but maybe
15:56:07 [nigel]
.. an example of how to use substitution to explain how it can be used to produce
15:56:12 [nigel]
.. inline graphics could be useful in TTML.
15:56:29 [nigel]
Vladimir: That would be fine [assuming that the spec is stuck to]
15:56:32 [nigel]
Cyril: I agree.
15:57:28 [nigel]
SUMMARY: TTWG to request ARIB for examples, and consider adding a substitution example to IMSC or TTML.
15:57:40 [nigel]
Nigel: I think I heard no proposals for substantive language about support for particular
15:57:41 [nigel]
.. features.
15:57:54 [nigel]
Cyril: I think Pierre [who left a moment ago] was saying we should wait for examples first.
15:57:59 [Vladimir]
just an illustration to my previously used example: https://www.myfonts.com/fonts/linotype/zapfino-extra/
15:58:27 [nigel]
Cyril: The action is to request this from ARIB as part of a general response?
15:58:28 [Vladimir]
the whole name is substituted with the glyph that represents the font name
15:58:40 [nigel]
Nigel: I would prefer to wait until we have covered the other ARIB issues but if it is going to
15:58:45 [nigel]
.. be many weeks then I would prefer to do it sooner.
15:58:50 [nigel]
Cyril: Yes that makes sense.
15:59:18 [cyril]
data:text/html,<div%20style="font:%2048px%20Zapfino">Zapfino<br>Zapfin%20o
16:00:02 [nigel]
Topic: Meeting close
16:00:31 [nigel]
Nigel: Thanks everyone. We're out of time so I'll adjourn now.
16:00:45 [nigel]
.. We didn't manage to get to Pierre's AOB point, so hopefully we can cover that off-line.
16:00:48 [nigel]
.. [adjourns meeting]
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Chair+ Gary
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zakim, end meeting
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As of this point the attendees have been Vladimir, Nigel, Atsushi, Pierre, Andreas, Gary, Cyril
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RRSAgent, please draft minutes v2
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I have made the request to generate https://www.w3.org/2020/05/28-tt-minutes.html Zakim
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I am happy to have been of service, nigel; please remember to excuse RRSAgent. Goodbye
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16:15:59 [github-bot]
#tt (18 lines buffered on "Meeting close")
16:16:00 [github-bot]
no GitHub URL to comment on
16:16:06 [nigel]
github-bot, end topic
16:16:10 [nigel]
github-bot, status
16:16:10 [github-bot]
nigel, This is wgmeeting_github_ircbot version 0.3.8, compiled from b9408f2deaad9c21743302005be9c892f2611f44, which is probably in the repository at https://github.com/dbaron/wgmeeting-github-ircbot/
16:16:10 [github-bot]
I currently have data for the following channels:
16:16:10 [github-bot]
#tt (no topic data buffered)
16:16:25 [nigel]
rrsagent, excuse us
16:16:25 [RRSAgent]
I see no action items