Re: [ttml2] All ISDs must end, but not all TTML documents must end

Please consider the semantics of ``ttp:mediaDuration`` as may impact this
issue.

https://w3c.github.io/ttml2/spec/ttml2.html#parameter-attribute-mediaDuration

On Tue, Nov 7, 2017 at 1:09 PM, Nigel Megitt via GitHub <sysbot+gh@w3.org>
wrote:

> nigelmegitt has just created a new issue for https://github.com/w3c/ttml2:
>
> == All ISDs must end, but not all TTML documents must end ==
> It is possible to construct a TTML document with an ISD that has an
> indefinite end time but it is not possible to express this in an isd:isd
> document, because the end attribute on the root element is required and
> <timeExpression> does not permit a value equivalent to the SMIL keyword
> "indefinite" - I will raise that as a separate issue.
>
> For example what ISD should be created for a TTML document with no `begin`
> or `end` attributes present at all?:
>
> ```xml
> <tt>
> <head/>
> <body>
> <div>
> <p>some text that is visible from 0s forever</p>
> </div>
> </body>
> </tt>
> ```
>
> I propose:
>
> * Make the `isd:isd/@end` attribute optional, so that its absence means
> "no end time".
> * Add a note that the restriction on `isd:sequence` that prevents
> overlapping ISDs means that an ISD with no `end` attribute must be the
> final ISD in the sequence.
>
>
>
> Please view or discuss this issue at https://github.com/w3c/ttml2/i
> ssues/484 using your GitHub account
>
>

Received on Tuesday, 7 November 2017 20:16:44 UTC