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15:00:24 <trackbot> Meeting: Timed Text Working Group Teleconference
15:00:24 <trackbot> Date: 29 August 2019
15:00:38 <cyril> Agenda: https://github.com/w3c/ttwg/issues/57
15:00:39 <nigel> nigel has changed the topic to: TTWG weekly webex. Today 1500 UTC. Agenda for 2019-08-29: https://github.com/w3c/ttwg/issues/57
15:00:46 <cyril> Chair: Nigel
15:00:51 <cyril> Present: Cyril, Nigel, Gary
15:00:55 <nigel> Log: https://www.w3.org/2019/08/29-tt-irc
15:00:59 <cyril> Topic: this meeting
15:01:15 <atsushi> (will join after i18n WG call ends, sorry)
15:01:31 <cyril> Present+ Glenn, Andreas
15:02:20 <cyril> scribe: Cyril
15:03:14 <cyril> Present+ Pierre
15:03:33 <cyril> nigel: today I did not put any Webvtt topic
15:03:38 <cyril> ... do you need anything?
15:03:42 <cyril> gkatsev: no
15:03:55 <cyril> nigel: I pulled out 1 dusty IMSC issue
15:04:08 <cyril> ... I don't know if we can get anything on the charter
15:04:26 <cyril> ... TPAC planning, we should spend at least 10min at the end because it's coming up quickly
15:04:37 <cyril> ... is there any AOB?
15:04:52 <cyril> atai2: I would like to give an update on the 360 activity
15:05:07 <cyril> glenn: I added an agenda label on some TTML2 issues
15:05:22 <cyril> ... issue 950 and PR 1137
15:05:53 <cyril> Topic: support for font in IMSC
15:06:05 <nigel> github: https://github.com/w3c/imsc/pull/485
15:06:17 <cyril> nigel: this PR was opened 22 days ago
15:06:25 <cyril> ... there was some comment on it
15:06:57 <cyril> ... there was a comment about choosing the compatibility with font
15:07:04 <cyril> ... the reference to 14496-22
15:07:23 <glenn> q+
15:07:34 <cyril> pal: the reason I referenced 14496-22
15:07:47 <cyril> ... is because in an IMF forum this the reference that has been suggested
15:07:52 <cyril> ... this is a reference to Open Type
15:07:59 <cyril> ... that's the first that came to mind
15:08:13 <cyril> ... because that's what's used in existing applications of IMSC
15:08:19 <nigel> q+
15:08:21 <cyril> ... when downloadable fonts are used
15:08:49 <cyril> glenn: I don't like refering to a content type format specification directly
15:08:58 <cyril> ... we should be referring to MIME media type values
15:09:12 <cyril> ... and refer to the definitions, like font/off
15:09:33 <cyril> ... I would like to see it changed
15:09:47 <cyril> ... rather than referring to the ISO specification
15:10:00 <cyril> pal: I'm comfortable with that
15:10:18 <cyril> ... I want to use font/otf
15:10:28 <cyril> glenn: fine for me
15:10:30 <nigel> q?
15:10:33 <nigel> ack gl
15:10:39 <cyril> q+
15:10:52 <cyril> nigel: Open Type fonts can be wrapped into WOFF
15:11:06 <cyril> ... is it the intention that WOFF or WOFF2 are not permitted?
15:11:36 <cyril> pal: on practical experience, font/otf will work
15:11:40 <cyril> ... people have been using it
15:11:49 <cyril> ... so mandating support for it is not an issue
15:12:05 <cyril> ... there are some politics/drama about WOFF
15:12:14 <cyril> ... I don't know what it means exactly
15:12:28 <nigel> -> https://drafts.csswg.org/css-fonts-3/#src-desc CSS font-face src descriptor
15:12:39 <cyril> ... but I'm uncomfortable with adding WOFF
15:12:51 <cyril> glenn: WOFF can take multiple types of fonts than OTF
15:13:02 <cyril> ... you would have to restrict WOFF
15:13:17 <cyril> ... I think I agree with Pierre on this
15:14:00 <cyril> nigel: the font-face src property lists many types of possible font faces
15:14:13 <cyril> ... CSS would allow other options that are being prevented here
15:14:17 <cyril> ... including SVG fonts
15:14:33 <cyril> ... which is interesting for the use case that we are trying to support (icons)
15:14:43 <atsushi> present+
15:14:56 <cyril> cyril: I'm not sure there is widespread support for SVG fonts
15:15:04 <cyril> glenn: agree with Cyril
15:15:22 <cyril> ... unless there is a strong support for a given font format it is fine to limit it to OTF for now
15:15:26 <cyril> ... we can add more later
15:15:51 <cyril> pal: until there is concrete explanation of why WOFF is necessary, I suggest sticking with OTF for now
15:16:08 <cyril> nigel: so the proposal is to adopt initially only OTF
15:16:17 <cyril> ... do we have consensus?
15:17:11 <cyril> cyril: I agree
15:17:23 <cyril> nigel: no objection
15:17:41 <cyril> RESOLUTION: IMSC font support will initially only support OTF
15:17:53 <cyril> q?
15:17:56 <cyril> ack nigel
15:18:48 <cyril> cyril: I would like to make sure that we have the right restrictions on the different elements and attributes
15:19:01 <cyril> nigel: there are similar comments in the issue
15:19:22 <cyril> ... about how the font element sources are defined and there seems to be a bit of ambiguity
15:19:32 <cyril> ... is it ok to have no sources for the font element or more than one
15:19:44 <cyril> ... my reading was that you needed 1 and may have more than one
15:19:56 <cyril> ... glenn suggested to have an src attribute
15:20:21 <cyril> pal: the reason I went the children way was to enable alternatives
15:20:35 <cyril> ... it wasn't clear to me that you could use multiple font elements
15:20:51 <cyril> glenn: you cannot have multiple font elements with the same family name
15:21:04 <cyril> pal: that's my guess but it was not clear in the spec
15:21:31 <cyril> glenn: the font family attribute can be a list of font family
15:21:36 <cyril> cyril: exactly
15:22:13 <cyril> glenn: you could have different font elements, each with an src attribute, and call them font1, font2, font3 and use these values in the fontstyle attribute
15:22:28 <cyril> pal: I did consider that but thought it wasn't clear
15:22:37 <cyril> ... that's why I ended up were we are
15:22:44 <cyril> s/were/where/
15:23:07 <cyril> nigel: I agree that the most elegant way to have alternative is to use multiple source elements
15:23:16 <cyril> ... but having zero elements does not make sense
15:23:20 <cyril> glenn: I agree
15:23:29 <nigel> s/glenn/pal
15:23:29 <cyril> s/glenn/pal/
15:24:23 <cyril> pal: my proposal is to say that TTML2 requires one source element to be present if the src attribute is not specified
15:24:40 <cyril> cyril: what is the use case for specifying alternatives?
15:24:58 <cyril> pal: if one source is broken, you have a choice for another one
15:25:18 <cyril> ... or a backup online vs embedded in the multiplex
15:25:29 <cyril> glenn: also switching between different types
15:25:34 <nigel> i/cyril: what/nigel: that works for me, thank you, and a note in the IMSC spec pointing out that at least one is required would help.
15:26:47 <cyril> cyril: I would hate to have 2 ways to do the same thing
15:27:22 <cyril> nigel: it's not clear how the fall back algorithm works
15:27:42 <cyril> glenn: using the range attribute you may have multiple fonts
15:28:46 <nigel> s/how the fall back algorithm works/that the fall back algorithms are the same for alternate sources vs alternate fontFamily
15:28:51 <cyril> cyril: I'd like to keep it simple for the simple use case
15:30:00 <cyril> pal: the basic use case is a font element 2 children, one for the multiplex and one for the online version, no glyph subset, etc.
15:30:36 <cyril> cyril: not even sure that this is the basic use case for Netflix, it could be even simpler
15:31:15 <cyril> ... I'm not saying the Netflix use case should be the only use case
15:31:34 <cyril> glenn: we don't have enough information about the use cases but we need an initial proposal
15:32:18 <cyril> nigel: the main question is do we allow a single source (with src attribute) or multiple sources (children and no src)
15:32:30 <cyril> ... at the moment we don't support multiple formats
15:33:10 <cyril> ... but supporting multiple source elements seems future looking
15:33:25 <cyril> pal: I did not want to have support for src attribute and source elements
15:34:52 <cyril> cyril: what about data?
15:35:09 <cyril> pal: the term external resource excludes using data
15:35:18 <cyril> glenn: external means not in the document
15:35:25 <cyril> pal: right, so no data
15:35:48 <cyril> cyril: I'm confused with "Partially supported via <code>#embedded-data</code>"
15:36:28 <cyril> nigel: I made a similar comment in the thread
15:36:32 <cyril> ... and made some suggestion
15:38:19 <cyril> Topic: TTML2 issues
15:38:45 <nigel> Topic: Add #direction-version-2 feature designator. w3c/ttml2#1024
15:38:50 <nigel> github: https://github.com/w3c/ttml2/issues/1024
15:39:15 <cyril> nigel: this PR covers special inheritance semantics
15:39:28 <cyril> ... adding direction to p is not a change as this was in TTML1
15:40:08 <cyril> ... Pierre do you think the new feature designator is not needed
15:43:13 <cyril> pal: I don't think we need a new designator, because it was clear in XSL before
15:43:27 <cyril> ... to the extent that you have to look at XSL, and it is unambiguous
15:43:46 <cyril> cyril: are you saying this behavior applies to TTML1 already?
15:43:58 <cyril> pal: I think so and I think IMSC.js supports that
15:44:02 <nigel> -> https://www.w3.org/TR/2006/REC-xsl11-20061205/#direction XSL definition
15:44:59 <cyril> nigel: I can see your point Pierre
15:45:13 <cyril> ... you might argue that TTML2 might benefit from a note about that
15:45:45 <cyril> ... the XSL specification says it is a modification compared to the CSS specification
15:46:06 <cyril> glenn: in TTML1, it says that it is based on XSL 1.1
15:46:32 <cyril> pal: IMSC.js code mentions XSL
15:46:48 <cyril> ... so this was already specified in TTML1
15:47:01 <nigel> -> https://www.w3.org/TR/css-writing-modes-3/#principal-flow CSS 3 Writing Modes section on Principal Writing Mode.
15:47:06 <cyril> glenn: so it would be useful to add a note, saying it's not new and closing this issue
15:47:13 <nigel> +1
15:47:14 <cyril> nigel: I agree
15:49:32 <nigel> Topic: Constrain maximum value of @length on data element. ttml2#1023
15:49:38 <nigel> github: https://github.com/w3c/ttml2/issues/1023
15:50:36 <cyril> glenn: the only place where it might be useful to have a constraint is when you have base64 data
15:50:49 <cyril> ... you could have an infinitely long document
15:51:02 <cyril> ... so I was proposing to limit that to 4GB
15:51:20 <cyril> cyril: Isn't this an application-level constraint
15:51:24 <cyril> nigel: yes
15:51:46 <cyril> glenn: application can do that so probably no need to put a constraint in the spec
15:51:53 <cyril> ... there is a difference in code
15:52:11 <cyril> ... if you are writing a validator, you cannot use a 32 bit integer for the size
15:52:21 <cyril> nigel: I propose to close the issue with no change
15:52:26 <cyril> ... any objection
15:52:41 <cyril> RESOLUTION: we close issue 1023 with no change
15:53:26 <cyril> Topic: TPAC
15:53:41 <cyril> nigel: there is a proposed time at 9:30 am to have a joint meeting with CSS
15:53:51 <cyril> ... I've requested a meeting with the Chinese IG
15:53:54 <cyril> ... but had no response yet
15:54:26 <atsushi> +1
15:54:33 <cyril> ... if you have an issue with that 9:30 time, send me a message otherwise I'll reply that we agree
15:54:42 <cyril> ... the wiki page has had some updates with topics
15:54:48 <cyril> ... we need to look at the schedule
15:55:01 <cyril> ... the week before TPAC I'll be travelling
15:55:17 <cyril> ... so next week is the last time when we could discuss this
15:55:39 <cyril> cyril: should we have a 2h meeting next week
15:55:44 <cyril> nigel: yes
15:56:00 <cyril> pal: I'll be avaiable only for 2nd hour
15:56:16 <cyril> s/avaiable/available
15:56:25 <cyril> nigel: anything else on TPAC?
15:56:42 <cyril> pal: I've changed my schedule and will be attending the IG from Monday
15:57:02 <cyril> Topic: 360 subtitles
15:57:16 <cyril> atai2: I've drafted an explainer for this activity with requirements
15:57:21 <cyril> ... sent it to the incubator
15:57:28 <cyril> ... will be discussed on monday at TPAC
15:57:44 <cyril> nigel: if this is not on the wiki page of TPAC, please add it
15:58:07 <cyril> Topic: TTML2 issue 950
15:58:19 <cyril> glenn: my only point is that I added one more comment
15:58:22 <nigel> github: https://github.com/w3c/ttml2/issues/950
15:58:29 <cyril> ... we cannot remove the set element, my explanation is there
15:58:39 <cyril> ... I verified that the algorithm needs it
15:59:00 <nigel> Topic: Constrain ttp:profile's @use attribute (#1029). ttml2#1137
15:59:06 <nigel> github: https://github.com/w3c/ttml2/pull/1137
15:59:37 <cyril> glenn: the PR has been opened for 27 days, I need a review
15:59:42 <nigel> Topic: Fonts
16:00:03 <cyril> pal: I ran into a problem in practice and wanted to know if people had it
16:00:33 <cyril> ... in Digital Cinema subs, you can do manual kerning at the markup level, specifying positive/negative spacing
16:00:48 <cyril> glenn: letter spacing can be used for that, including negative
16:01:00 <cyril> pal: is there a reason to do that in the markup vs in the font?
16:01:14 <cyril> ... I've seen fonts with no embedded kerning at all
16:01:34 <cyril> glenn: many CJK fonts have fixed width for all glyphs and no kerning
16:01:41 <cyril> ... it's not unusual
16:02:03 <cyril> ... if it's an open type font you can use a gpos table
16:02:14 <cyril> ... to fine tune the position based on context
16:02:19 <cyril> ... it can be done in the fonts
16:02:31 <cyril> ... TTPE supports gpos and gsub
16:02:45 <cyril> pal: that's my understanding
16:02:58 <cyril> ... is there any reason why someone would not want to do it at the font level?
16:03:12 <cyril> glenn: lack of access to changing the font, IPR reasons for example
16:03:39 <cyril> pal: the font that I saw was a subset so the font had been modified, so the IPR argument does not hold
16:04:16 <cyril> nigel: glenn said you can put a single character in a span and apply letter spacing, where would the spacing apply: before or after?
16:04:32 <cyril> glenn: you'd have to put it around a pair of characters
16:04:44 <cyril> ... with some limitation that you cannot overlap the markup
16:06:15 <cyril> Topic: meeting close
16:06:41 <atai2> atai2 has left #tt
16:06:44 <cyril> rrsagent, pointer
16:06:44 <RRSAgent> See https://www.w3.org/2019/08/29-tt-irc#T16-06-44
16:07:00 <nigel> scribe: nigel
16:07:22 <nigel> Nigel: Thanks everyone, we're over time, so I'll adjourn now. 2 hour meeting next week so we'll begin an hour earlier. [adjourns meeting]
16:07:25 <nigel> rrsagent, make minutes
16:07:25 <RRSAgent> I have made the request to generate https://www.w3.org/2019/08/29-tt-minutes.html nigel
16:08:35 <nigel> s/adjourn now./adjourn now. Thank you Cyril for scribing.
16:30:35 <nigel> rrsagent, make minutes
16:30:35 <RRSAgent> I have made the request to generate https://www.w3.org/2019/08/29-tt-minutes.html nigel
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16:32:35 <nigel> rrsagent, make minutes
16:32:35 <RRSAgent> I have made the request to generate https://www.w3.org/2019/08/29-tt-minutes.html nigel
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