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RE: beginEnd002: par timeContainer and child with no duration

From: John Birch <john.birch@screen.subtitling.com>
Date: Tue, 16 Dec 2008 09:38:17 -0000
Message-ID: <4476B296B92A4741A49B0BD017590700AA7A2D@sss-uk-ex-02.screen.subtitling.local>
To: "Geoff Freed" <geoff_freed@wgbh.org>, "Sean Hayes" <Sean.Hayes@microsoft.com>, <public-tt@w3.org>

Geoff wrote 

"...i would lobby for changing the spec, if it's not a big pain, to
permit this behavior not only because it's less work, but also because
caption vendors will probably expect to be able to do things this
way...."

Actually, the concept of 'no end time' causes no end (sic) of problems
in the captioning / subtitling world !
All professional subtitle file formats I am aware of include an end time
for all subtitles.
Even back to back presentation is coded with a start and end time for
each presented subtitle.
(In fact it is typical to include a 3, 4 or 5 frame gap between
subtitles in order to force a visible redraw on the screen.)

The concept of 'no end time' seems (as an outside observer) primarily
related to US caption practices... Perhaps it is in part related to the
roll-on caption style. In the US caption system the viewer has
considerably more control over the size and shape of the region and more
importantly the way the region is cleared, than in any other form of
broadcast captioning.

Many early set-top boxes for the DVB subtitling standards did not honour
end timing, instead anticipating that a following subtitle or clear down
would restore the intended presentation. Unfortunately they also omitted
to clear the subtitle duispaly on changing channels, and further assumed
that subtit;e display would continmue during advert breaks. Of course,
translation subtitles are rarely required during ad breaks (as these are
locally produced or localised) so often these early set-top boxes would
leave a subtitle hanging over the entire ad break (or until an internal
timeout). Needless to say the advertisers on those channels were very
vocal about resolving that issue ;-)

So, yes please, let's have a very clear statement of timing intent,
without implicit or assumed durations. After all, the conversion between
a 'no end time' and a precisely timed form of a presentation is
something that could be trivially automated?

Regards,

John

John Birch | Screen Subtitling Systems Ltd | Strategic Partnerships Manager
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-----Original Message-----
From: public-tt-request@w3.org [mailto:public-tt-request@w3.org] On
Behalf Of Geoff Freed
Sent: 16 December 2008 00:52
To: Sean Hayes; public-tt@w3.org
Subject: RE: beginEnd002: par timeContainer and child with no duration



i agree with sean's explanation, as this is the expected behavior
according to dfxp now.  however, when we built ccplayer we implemented
things a bit differently-- that is, a caption that has a begin time but
no end time or dur will display until the next caption displays.  at
that time, the first caption will erase just before the next caption
appears.  so in the case of this:

      <p begin='1s'>This test counts from 0 to 10 in 10
seconds.<br/>1</p>
      <p begin='2s'>This test counts from 0 to 10 in 10
seconds.<br/>2</p>
      <p begin='3s'>This test counts from 0 to 10 in 10
seconds.<br/>3</p>

the first caption appears at 1s and is displayed until 2s, at which time
it erases and the second caption displays.  at 3s, the second caption
erases and the third caption displays.  etc., etc.  in dfxp terms, that
equals this:

      <p begin='1s' end='2s'>This test counts from 0 to 10 in 10
seconds.<br/>1</p>
      <p begin='2s' end='3s'>This test counts from 0 to 10 in 10
seconds.<br/>2</p>
      <p begin='3s' end='4s'>This test counts from 0 to 10 in 10
seconds.<br/>3</p>


we did things this way because caption software has not always depended
on end times to erase captions when the captions are timed to appear
sequentially without pause.

doing things the first way means less coding, which is convenient.  i
would lobby for changing the spec, if it's not a big pain, to permit
this behavior not only because it's less work, but also because caption
vendors will probably expect to be able to do things this way.

geoff




________________________________________
From: public-tt-request@w3.org [public-tt-request@w3.org] On Behalf Of
Sean Hayes [Sean.Hayes@microsoft.com]
Sent: Monday, December 15, 2008 5:26 PM
To: public-tt@w3.org
Subject: RE: beginEnd002: par timeContainer and child with no duration

Slight update. The last p (the test is over) is removed at 20s. The
other p's remain however.

Sean Hayes
Media Accessibility Strategist
Accessibility Business Unit
Microsoft

Office:  +44 118 909 5867,
Mobile: +44 7875 091385


-----Original Message-----
From: public-tt-request@w3.org [mailto:public-tt-request@w3.org] On
Behalf Of Sean Hayes
Sent: 15 December 2008 22:17
To: Philippe Le Hegaret; public-tt@w3.org
Subject: RE: beginEnd002: par timeContainer and child with no duration


Assuming the document is surrounded by the appropriate verbiage, then I
believe it is conforming. (NB SMIL explicitly disallows 0s, but it is
allowed in our spec). Under a seq default for body no output would be
produced, assuming we are changing body to be par, then the expected
output is shown below.
BTW I'm almost done writing a whole bunch of tests for timing and
animation, should be posting these in a few days.

This output is not particularly self explanatory. Each p, being in a par
context has indefinite duration. Each one has an onset time one second
later than its predecessor.

The expected behaviour is

at time 00:00:00
This test counts from 0 to 10 in 10 seconds.
0

at time 00:00:01
This test counts from 0 to 10 in 10 seconds.
0
This test counts from 0 to 10 in 10 seconds.
1

at time 00:00:02
This test counts from 0 to 10 in 10 seconds.
0
This test counts from 0 to 10 in 10 seconds.
1
This test counts from 0 to 10 in 10 seconds.
2

at time 00:00:03
This test counts from 0 to 10 in 10 seconds.
0
This test counts from 0 to 10 in 10 seconds.
1
This test counts from 0 to 10 in 10 seconds.
2
This test counts from 0 to 10 in 10 seconds.
3

And so on until

at time 00:00:10

This test counts from 0 to 10 in 10 seconds.
0
This test counts from 0 to 10 in 10 seconds.
1
This test counts from 0 to 10 in 10 seconds.
2
This test counts from 0 to 10 in 10 seconds.
3
This test counts from 0 to 10 in 10 seconds.
4
This test counts from 0 to 10 in 10 seconds.
5
This test counts from 0 to 10 in 10 seconds.
6
This test counts from 0 to 10 in 10 seconds.
7
This test counts from 0 to 10 in 10 seconds.
8
This test counts from 0 to 10 in 10 seconds.
9
This test counts from 0 to 10 in 10 seconds.
10


at time 00:00:11

This test counts from 0 to 10 in 10 seconds.
0
This test counts from 0 to 10 in 10 seconds.
1
This test counts from 0 to 10 in 10 seconds.
2
This test counts from 0 to 10 in 10 seconds.
3
This test counts from 0 to 10 in 10 seconds.
4
This test counts from 0 to 10 in 10 seconds.
5
This test counts from 0 to 10 in 10 seconds.
6
This test counts from 0 to 10 in 10 seconds.
7
This test counts from 0 to 10 in 10 seconds.
8
This test counts from 0 to 10 in 10 seconds.
9
This test counts from 0 to 10 in 10 seconds.
10

This test is over.


This then remains onscreen until the outer tt ends (controlled by
external forces).


Sean Hayes
Media Accessibility Strategist
Accessibility Business Unit
Microsoft

Office:  +44 118 909 5867,
Mobile: +44 7875 091385


-----Original Message-----
From: public-tt-request@w3.org [mailto:public-tt-request@w3.org] On
Behalf Of Philippe Le Hegaret
Sent: 15 December 2008 21:44
To: public-tt@w3.org
Subject: beginEnd002: par timeContainer and child with no duration


We currently have the test beginEnd002 as follows:
[[
  <body>
    <div>
      <p begin='0s'>This test counts from 0 to 10 in 10
seconds.<br/>0</p>
      <p begin='1s'>This test counts from 0 to 10 in 10
seconds.<br/>1</p>
      <p begin='2s'>This test counts from 0 to 10 in 10
seconds.<br/>2</p>
      <p begin='3s'>This test counts from 0 to 10 in 10
seconds.<br/>3</p>
      <p begin='4s'>This test counts from 0 to 10 in 10
seconds.<br/>4</p>
      <p begin='5s'>This test counts from 0 to 10 in 10
seconds.<br/>5</p>
      <p begin='6s'>This test counts from 0 to 10 in 10
seconds.<br/>6</p>
      <p begin='7s'>This test counts from 0 to 10 in 10
seconds.<br/>7</p>
      <p begin='8s'>This test counts from 0 to 10 in 10
seconds.<br/>8</p>
      <p begin='9s'>This test counts from 0 to 10 in 10
seconds.<br/>9</p>
      <p begin='10s'>This test counts from 0 to 10 in 10
seconds.<br/>10</p>
      <p begin='11s' end='20s'>This test is over.</p>
    </div>
  </body>
]]

What is the expected behavior?

1- give up because the document is not conforming

2- only shows the last paragraph from 11 to 20 because the other
paragraphs have unresolved durations (that's the behavior of JW FLV
Media Player)

3- all paragraphs will end at 20 (and begin at their respective times)
because at least one of the children has a resolved duration

4- the first 11 paragraphs will show for one second each and the last
paragraph will show from 11 to 20 (that's what ccPlayer and Adobe are
doing)


Philippe










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Received on Tuesday, 16 December 2008 09:39:00 GMT

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