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Re: ISSUE-313 (Presented Region is informative only): Presented Region section is informative only [TTML IMSC 1.0]

From: Nigel Megitt <nigel.megitt@bbc.co.uk>
Date: Mon, 21 Jul 2014 16:44:31 +0000
To: Glenn Adams <glenn@skynav.com>
CC: Pierre-Anthony Lemieux <pal@sandflow.com>, Timed Text Working Group <public-tt@w3.org>
Message-ID: <CFF3016C.2059B%nigel.megitt@bbc.co.uk>
However I note that we haven't resolved whether there is any substantive
difference between 'presented region' in IMSC 1 and 'temporally active
region' in TTML 1 SE. If they are synonymous and as a result of Issue-314
we add an erratum to TTML 1 SE to define "temporally active region" then
we should modify IMSC 1 to use that term in place of "presented region".

I think they are not synonymous since a temporally active region may not produce any renderable pixels (i.e., not be presented) for a number of reasons, including:

  *
  *   extent is zero in some dimension
  *   origin is such that region doesn't intersect with root container region
  *   display is none

  *   visible is hidden
  *   opacity is 1

These are good considerations from the current wording however I'm not sure that the intention was to make them different  Pierre, perhaps IMSC should include these factors in the definition of presented region, additionally?

Kind regards,

Nigel


On 21/07/2014 17:39, "Glenn Adams" <glenn@skynav.com<mailto:glenn@skynav.com>> wrote:




On Mon, Jul 21, 2014 at 4:08 AM, Nigel Megitt <nigel.megitt@bbc.co.uk<mailto:nigel.megitt@bbc.co.uk>> wrote:
Hi Pierre,

s/A presented region is a region that satisfies all of the following
conditions are true:/A presented region is a region that satisfies all of
the following conditions:

Then this is acceptable to me to close Issue-313, as discussed.

However I note that we haven't resolved whether there is any substantive
difference between 'presented region' in IMSC 1 and 'temporally active
region' in TTML 1 SE. If they are synonymous and as a result of Issue-314
we add an erratum to TTML 1 SE to define "temporally active region" then
we should modify IMSC 1 to use that term in place of "presented region".

I think they are not synonymous since a temporally active region may not produce any renderable pixels (i.e., not be presented) for a number of reasons, including:

  *
  *   extent is zero in some dimension
  *   origin is such that region doesn't intersect with root container region
  *   display is none

  *   visible is hidden
  *   opacity is 1

These are good considerations from the current wording however I'm not sure that the intention was to make them different  Pierre, perhaps IMSC should include these factors in the definition of presented region, additionally?


Also, I note from 2.3 in [1] that it is both a requirement to define
terms and a good practice ("Good Practice 9" also in [1]) to consolidate
the definitions in a glossary section. I will raise a separate issue that
IMSC 1 needs to meet the requirements of this document and as far as
possible also the good practices.

Kind regards,

Nigel

[1] QA Framework: Specification Guidelines
http://www.w3.org/TR/qaframe-spec/#define-terms-section



On 20/07/2014 23:03, "Pierre-Anthony Lemieux" <pal@sandflow.com<mailto:pal@sandflow.com>> wrote:

>Hi Nigel,
>
>Please indicate whether the text at [1] resolves your comment per your
>suggestion at [2].
>
>[1]
>https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml-ww-profiles/ttml-ww-profiles
>.html#presented-region
>[2] http://www.w3.org/AudioVideo/TT/tracker/issues/313
>
>Thanks,
>
>-- Pierre
>
>On Wed, May 21, 2014 at 6:03 AM, Timed Text Working Group Issue
>Tracker <sysbot+tracker@w3.org<mailto:sysbot%2Btracker@w3.org>> wrote:
>> ISSUE-313 (Presented Region is informative only): Presented Region
>>section is informative only [TTML IMSC 1.0]
>>
>> http://www.w3.org/AudioVideo/TT/tracker/issues/313
>>
>> Raised by: Nigel Megitt
>> On product: TTML IMSC 1.0
>>
>> The definition of Presented Region [1] appears intended to add no
>>information relative to what is in TTML1SE. I suggest making it
>>informative rather than normative.
>>
>> However it does differ in that in TTML1SE temporally active regions
>>with opacity=0 will be included in the intermediate synchronic document
>>construction. Note that TTML1SE does not actually define "temporally
>>active" directly as used in 9.3.2 Intermediate Synchronic Document
>>Construction (though it may be implied by reference to SMIL semantics).
>>Therefore another solution to this issue would therefore be to rephrase
>>in terms of a localised definition of "temporally active" as applied to
>>regions.
>>
>> For example:
>>
>> A region, as defined in [TTML1], is considered temporally active if all
>>of the following conditions are true:
>> ...
>>
>> Arguably this should be captured in an errata to TTML1SE and not needed
>>in IMSC 1.0 at all.
>>
>> [1] http://www.w3.org/TR/ttml-imsc1/#presented-region
>> [2] http://www.w3.org/TR/ttml1/#semantics-region-layout-step-1
>>
>>
>>
Received on Monday, 21 July 2014 16:45:03 UTC

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