W3C home > Mailing lists > Public > public-tt@w3.org > December 2008

RE: beginEnd002: par timeContainer and child with no duration

From: Geoff Freed <geoff_freed@wgbh.org>
Date: Tue, 16 Dec 2008 06:49:29 -0500
To: "Glenn A. Adams" <gadams@xfsi.com>, "public-tt@w3.org" <public-tt@w3.org>
Cc: Sean Hayes <Sean.Hayes@microsoft.com>
Message-id: <E36081A12A13F146AC32D7724B0E8912060C331394@EXCHCCR.wgbh.org>


well, granted it's not the strongest of cases and would, as others have pointed out, lead to ambiguous timing situations, but i wanted to float the proposal anyhow.  ccplayer's behavior with regards to captions having begin with no dur or end may be problematic in the test cases, however.

onward...

g.

________________________________________
From: Glenn A. Adams [gadams@xfsi.com]
Sent: Monday, December 15, 2008 10:29 PM
To: Silvia Pfeiffer; Geoff Freed
Cc: Sean Hayes; public-tt@w3.org
Subject: RE: beginEnd002: par timeContainer and child with no duration

I also agree with Silvia, and would oppose the change suggested by
Geoff. The proposed change would be a significant departure from SMIL
timing semantics, which we have tried to maintain.

Geoff, a better way for you to express what you want would be:

<div timeContainer="seq">
<p dur='1s'>This test counts from 0 to 10 in 10 seconds.<br/>0</p>
<p dur='1s'>This test counts from 0 to 10 in 10 seconds.<br/>1</p>
<p dur='1s'>This test counts from 0 to 10 in 10 seconds.<br/>2</p>
<p dur='1s'>This test counts from 0 to 10 in 10 seconds.<br/>3</p>
...
<p dur='1s'>This test counts from 0 to 10 in 10 seconds.<br/>10</p>
<p end='10s'>This test is over.</p>
</div>

G.

> -----Original Message-----
> From: public-tt-request@w3.org [mailto:public-tt-request@w3.org] On
Behalf Of Silvia
> Pfeiffer
> Sent: Tuesday, December 16, 2008 9:41 AM
> To: Geoff Freed
> Cc: Sean Hayes; public-tt@w3.org
> Subject: Re: beginEnd002: par timeContainer and child with no duration
>
>
> 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 11:55:50 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 2 November 2009 22:41:39 GMT