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Re: ISSUE-330 (Is Presented Region a synonym for temporally active region?): Is Presented Region a synonym for temporally active region? [TTML IMSC 1.0]

From: Nigel Megitt <nigel.megitt@bbc.co.uk>
Date: Wed, 13 Aug 2014 09:35:57 +0000
To: Pierre-Anthony Lemieux <pal@sandflow.com>
CC: Glenn Adams <glenn@skynav.com>, Timed Text Working Group <public-tt@w3.org>
Message-ID: <D010EB29.FAAA%nigel.megitt@bbc.co.uk>
Hi Pierre,

Iıve added a note to ISSUE-330, quoted here for convenience:

The updated text uses phrases such as Œearlier/later in the documentı -
this does not address my original concern, that the test for earlier and
later is not precisely enough defined. Do you mean to compare the byte
locations of the opening tag of the elements in the flattened document
structure, for example?

It is also unclear in the new wording (list item 2) how an ISD ³maps² to a
content element. An ISD is typically constructed from multiple elements
simultaneously. There seems to be an assumption that an ISD can only
relate to a single p, which is such a significant constraint that I wonder
if it was intended.

Take this example:

<p id="p1" begin="00:01:00" end="00:02:00">
[some stuff]
<p id="p2" begin="00:01:30" end="00:01:45">
[some other stuff]

We have here the following ISDs:
1. 00:01:00 containing p1
2. 00:01:30 containing p1 and p2
3. 00:01.45 containing p1
4. 00:02:00 containing nothing

Is this progressively decodable? Did the 3rd ISD above 'map' to p2? It
doesn't itself contain p2: it simply has its timing derived from p2.

Kind regards,


On 12/08/2014 15:51, "Pierre-Anthony Lemieux" <pal@sandflow.com> wrote:

>Addressed at https://dvcs.w3.org/hg/ttml/rev/ceaa219bfbcc .
>-- Pierre
>On Mon, Jul 28, 2014 at 5:55 PM, Nigel Megitt <nigel.megitt@bbc.co.uk>
>> Thanks for the clarification Glenn. I've added a note to ISSUE-330 which
>> I'll quote to save clicks:
>> "In that case it would make sense to define 'presented region' in terms
>>of a
>> 'temporally active region' that either contains visible content with
>>>0 or has showBackground="always" and a backgroundColour with opacity
>> Nigel
>> On 28/07/2014 16:41, "Glenn Adams" <glenn@skynav.com> wrote:
>> No, temporally active region and presented region are not synonymous.
>> Further, showBackground="whenActive" does not mean "when temporally
>> rather it means "when temporally active and has content selected into
>> As such it is a bit of a misnomer, but we adopted the name from SMIL and
>> repurposed it to our ends.
>> See my additional comments in Issues 314 and 330.
>> On Mon, Jul 28, 2014 at 6:56 AM, Timed Text Working Group Issue Tracker
>> <sysbot+tracker@w3.org> wrote:
>>> ISSUE-330 (Is Presented Region a synonym for temporally active
>>> Is Presented Region a synonym for temporally active region? [TTML IMSC
>>> http://www.w3.org/AudioVideo/TT/tracker/issues/330
>>> Raised by: Nigel Megitt
>>> On product: TTML IMSC 1.0
>>> This issue is related to Issue-314 and was generated as part of the
>>> resolution to Issue-313.
>>> TTML 1 SE §9.3.2 [1] uses the term "temporally active region" to define
>>> regions that are included in the construction of intermediate
>>> documents "for the purposes of performing presentation processing".
>>> Issue-314 covers the point that this term is not defined.
>>> [1] http://www.w3.org/TR/ttml1/#semantics-region-layout-step-1
>>> IMSC 1 editor's draft §4.6.1 [2] defines and uses the term "presented
>>> region" to define regions that may be presented at any moment, and in
>>> but one case references presented region with respect to an
>>> synchronic document.
>>> [2]
>>> It looks as though these two terms may be synonyms, or very closely
>>> related to each other. If this is the case then IMSC 1 should
>>>reference the
>>> defined term in TTML 1 SE (if need be, after the resolution to
>>> If it is not the case then the difference should be clarified making
>>> reference to the similar concept.
>>> For example, if the resolution to Issue-314 is to define temporally
>>> region in TTML 1 SE as any region that is either temporally active or
>>> content selected into it that is temporally active, or has
>>> showBackground="always", then Presented Region in IMSC 1 may be
>>>defined as:
>>>    any temporally active region which satisfies all of the following
>>> conditions...,
>>>    where those conditions include [those currently specified] and those
>>> noted additionally by Glenn in response to Issue-313 [3], i.e. the
>>>values of
>>> the attributes tts:display, tts:visibility, tts:extent and tts:opacity
>>> such that marks may be made by the region or its contents.
>>> [3] http://lists.w3.org/Archives/Public/public-tt/2014Jul/0036.html
>>> This issue created as per Action-308.
Received on Wednesday, 13 August 2014 09:36:28 UTC

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