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Re: beginEnd002: par timeContainer and child with no duration

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Tue, 16 Dec 2008 12:40:31 +1100
Message-ID: <2c0e02830812151740o4ba9061dkb9a26e7f20cf660a@mail.gmail.com>
To: "Geoff Freed" <geoff_freed@wgbh.org>
Cc: "Sean Hayes" <Sean.Hayes@microsoft.com>, "public-tt@w3.org" <public-tt@w3.org>

On Tue, Dec 16, 2008 at 11:51 AM, Geoff Freed <geoff_freed@wgbh.org> wrote:
>
>
> 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.

I respectfully disagree.

To me, upon first reading the first example, it was clear that this
would add a new caption every second, but not remove any of the ones
before. This is a very convenient way of specifying a default end
value of "this last until the video ends whenever it ends". The best
means to support this is by not giving an end value and therefore
allowing it to last "forever". And it allows to have overlapping timed
text that lasts until the end.

I think that if you wanted a text removed at a certain time, you'd
have to provide an end time. Otherwise you are open to all sorts of
misunderstandings. For example, what would you do with a specification
like this:

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

Would the third one appear at all?

Best Regards,
Silvia.
Received on Tuesday, 16 December 2008 01:41:19 GMT

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