See also: IRC log
<scribe> scribe: nigel
Nigel: For today we have some updates on IMSC and some TTML issues. Any other business?
group: [no other business]
Nigel: Next week I will not be available, and nobody has offered to Chair. Any volunteers?
Andreas: I may also not be able to attend next week.
Nigel: If anyone does want to
Chair next week's meeting please let me know by Tuesday
... at the latest and I will be able to assist with any queries
etc.
... Otherwise the default position may be that we do not hold a
meeting.
Nigel: My update is that after
publishing the WD for Wide Review Thierry sent the
horizontal
... review and internal dependency review messages out to other
W3 groups.
Thierry: I have sent the
questionnaire to the group and that is holding back the request
to
... TAG. That's the only one that is pending.
Nigel: Thank you. And I sent all
the external liaisons. It turns out that DLNA is no
longer
... operating, so I could not send to them. I got several
responses back from people saying
... they had received it and would provide feedback.
... Thierry sent that questionnaire out on 24th March. Any
queries on that now?
Thierry: I reused the wording
from TTML. Probably what may be missing is stuff about
the
... use of images in IMSC1.
Nigel: I see that the answer to 3.6 needs editing to remove audio and condition for example.
Thierry: Ok
Nigel: If you make those edits
then we can approve the updated text by email. I think
the
... remaining responses are uncontroversial.
Thierry: I will do that right now.
Nigel: We had one issue raised on IMSC this week that is of some interest:
https://github.com/w3c/imsc/issues/224
Nigel: This is about whitespace handling.
Glenn: The issue here is that the
wording of XSL-FO makes it hard for me to determine if
... the intent is to fully translate all whitespace that is XML
whitespace into 0x20 space characters.
Nigel: I had the same issue, I
wasn't sure exactly what it was trying to say or if there is
some
... order of precedence in applying the various rules.
Glenn: The problematic part is
whether or not collapse semantics apply, and it seems
like
... you can read it that for the first character in a sequence
of whitespace, if it is not a space,
... then you might not collapse it. I do not think that is the
intent and I do not know of any
... implementation that does not translate tab in that context
into space, so I think implementations
... should collapse it.
Nigel: I think my colleague Chris
(who raised the issue) has an implementation that seems
... to have this behaviour of retaining the first tab, and
seems to obey the letter of the
... specification rather than the intent.
Glenn: I think the Antenna House
and FOP implementations do it differently, so the
question
... is I guess what we really want to happen. If we want that
tab to be normalised to space
... then we need to fix up our spec. My suggestion is to add
language to TTML1 and TTML2
... to have that effect. Even if we do not translate it into
space there is certainly no suggestion
... that it be translated into an alignment or some spaces.
Nigel: Even if no alignment and no spaces a tab would be expected to have some inline width.
Glenn: Usually a tab character is
not in a font and is mapped to zero width. It has no
... inherent width semantics.
... Probably any fonts that do have a tab character map it to
zero width or to the space glyph.
Andreas: I have a question
regarding Chris's original question. He asked on the basis
of
... Example 7 of IMSC 1.0.1?
Nigel: Yes.
Andreas: So actually we did not provide the source for the example?
Nigel: Yes, we do.
... The way the spec is structured the example is an XML
document that is imported by the
... HTML and then formatted. So the tabs are really there.
Glenn: We should fix the example.
https://www.w3.org/TR/ttml-imsc1.0.1/#itts-fillLineGap
Nigel: Yes I agree and Pierre has indicated he agrees with that, on the issue.
Glenn: I agree with Andreas
however, that said, I think we should remove the tabs.
... There's another property called whitespace-treatment
...
Nigel: There are 4 properties defined by TTML1:
https://www.w3.org/TR/ttml1/#content-attribute-space
Glenn: If you look at §7.16.8 in XSL 1.1 on whitespace treatment:
<glenn> https://www.w3.org/TR/xsl/#white-space-treatment
Nigel: Since we use
suppress-at-line-break=auto that means only U+0020 is
suppressed,
... and everything else is retained.
Glenn: Correct.
... Under §1.2.1 under paging and scrolling it talks about
splitting things like whitespace
... into separate properties for greater control. The intent
was to derive those properties
... from CSS2, in this case the CSS2 property called
"whitespace". So to follow the implementation
... path of other implementations we probably want to go and
look at CSS2 whitespace.
<glenn> https://www.w3.org/TR/REC-CSS2/cover.html#minitoc
Glenn: The initial value of
whitespace is "normal" which directs user agents to
... "collapse sequences of whitespace, and break lines as
necessary to fill line boxes"
... and does not make a distinction between different kinds of
whitespace.
Nigel: If you follow the link it defines whitespace as:
-> "Only the characters "space" (Unicode code 32), "tab" (9), "line feed" (10), "carriage return" (13), and "form feed" (12) can occur in whitespace. "
Glenn: Exactly. These are the
same as XML whitespace. It looks like there's a bug in XSL-FO
here.
... I wonder if this was updated in a later version of
XSL-FO.
... Perhaps Steve Zilles would be a good person to ask about
this.
Andreas: I think we could also contact Tony Graham who is at Antenna House.
Glenn: We should certainly contact Steve as he is still active in W3C whereas Tony is not.
Nigel: Which should we do first, contact Steve or create the issues on TTML?
Glenn: I will create the issues
and link them to the IMSC issue from Chris and articulate
... the problem as I see it and then we can use that as
reference material in an email to
... Steve and Tony.
... I know both Steve and Tony so I can ask them. Since I chair
the Apache group on FOP
... I have a link there too.
Nigel: Okay, that's a plan, thank
you.
... I will add a note to the issue.
https://github.com/w3c/imsc/issues/224#issuecomment-290434056
https://github.com/w3c/ttml2/issues/233
Nigel: This raised some eyebrows,
since there was already a pull request that Pierre had
... opened on request.
Glenn: I always edit pull
requests before applying them to add my imprimatur and
make
... sure they are consistent.
<tm> using PR is not 10 yeras of process ...
Nigel: From a process point of
view, we had https://github.com/w3c/ttml2/pull/283
which
... the Group requested from Pierre to resolve the issue he
raised, which was closed without
... any communication and it was not obvious why. The branch
for the pull request could
... easily have been modified in place rather than closing and
opening a new one, which
... would have been less work and would have made the
provenance clearer.
Glenn: One thing here was that
the branch was not properly named and had things in
... which were not done in the right way. There was no
intention to raise tensions.
Andreas: This is an interesting
discussion - things like GitHub have changed the way that
... groups can collaborate on specification texts. I think we
appreciate that the Editor here
... has a different view maybe. We as a Group should decide on
what the process is that
... we use, and also recall that proposals and changes can be
made onto the pull requests.
Nigel: By the way you can rename a branch if that is the issue.
Glenn: It is not so
straightforward because the pull request doesn't get modified.
It is okay
... to do it locally before pushing to the remote, but when
pushing to the remote things
... get locked in.
... The only substantive point on this particular issue is the
name. I've stated my opinion
... on that. I don't think adding length to the name has any
improvement. That's my opinion.
Nigel: The name needs to reflect
the scope of application, which is much narrower than it
... is specified at the moment, and appears to apply to all HDR
content rather than
... just those HDR schemes that require it.
... This also needs to be reflected in the specification text,
which likewise needs
... to be narrowed to schemes such as PQ HDR.
Glenn: Looking at the original
proposal, that referred to images, which I took out.
... I took "image" to refer to the content on which it is
composited rather than a referenced
... PNG or JPEG image in an <image> element. Is that not
right?
Nigel: No that's correct I think it is about the video images, for example.
Glenn: Pierre used the term
"target image" and I changed it to "target medium" - I
found
... ways to eliminate the use of "image".
... The other thing is that the example has the unexplained
value 2.4 so I added "where the
... exponent of 2.4 is the gamma correction applied by the
EOTF". I may have been wrong
... in that but that was my interpretation.
... Just below the syntax box there is an equation that uses
the term "normalized" which
... I assume meant application of the gamma of 2.4.
Nigel: That's the root of the
problem - there is another scheme for HDR that does not
use
... the luminance gain approach at all but uses a different
approach varying the gamma.
<glenn> https://en.wikipedia.org/wiki/Gamma_correction
Andreas: I have to drop off now. Thank you.
Nigel: By specifying
tts:luminance and using this kind of wording it looks as though
we are
... promoting one particular scheme for HDR, which is not what
we should be doing at all.
Glenn: I was not aware of that context.
<tm> OK bye
Thierry: [drops off call]
Glenn: I did not make any other
changes here.
... Actually I did fix another change which was an error - he
had an integer type but in the
... examples used non-integer numbers so I changed to a
non-negative real number.
... I also added continuous animation support. Any numerical
value I make continuous.
Nigel: By the way the other
colour space that is often used is BT.2020 - we currently
only
... refer to BT2100 in Appendix P. So there needs to be some
work here to make this
... more neutral.
Glenn: Please note that people
file new issues on the text rather than piling comments
on
... to the original issue. We can always point back to the
original issue.
Nigel: Can I just check - are
there other branches with work in progress on them that
... are not yet complete and might be worth review?
Glenn: I have about 10,
particularly Audio Description. I'm hoping we do not slide too
far
... beyond the end of the month. The other one that is higher
up on my list is the one that
... came up last week regarding Andreas's pull request on
TTML1.
Nigel: I see that just Glenn and I remain on the call so we should probably close!
Glenn: I will take a look at Andreas's pull request and may need to make some changes to it.
Nigel: If you can edit the branch
that is the source of the pull request that will be
better.
... Even if you commit directly to that branch.
Glenn: Okay I will give that a go.
Nigel: Ok thanks, see you in a couple of weeks. [adjourns meeting]