ISSUE-338: inconsistent implicit duration of singleton span in sequential container
inconsistent implicit duration of singleton span in sequential container
- State:
- OPEN
- Product:
- TTML 1.0
- Raised by:
- Glenn Adams
- Opened on:
- 2014-08-26
- Description:
- The implicit duration of an anonymous span child of a sequential container is explicitly defined to be zero (section 10.4); however, the implicit duration of an explicit singleton (i.e., non-nested) span in the same context
Here is an example, where I ignore whitespace to aid in viewing. Given a fragment:
<p timeContainer="seq">
Foo
<span>Bar</span>
Baz
</p>
Generating anonymous spans to wrap text nodes:
<p timeContainer="seq">
<span xml:id="anon1">Foo</span>
<span>
<span xml:id="anon2">Bar</span>
</span>
<span xml:id="anon3">Baz</span>
</p>
Applying timing semantics as presently defined to resolve implicit duration:
<p timeContainer="seq" durImplicit="indefinite">
<span xml:id="anon1" durImplicit="0">Foo</span>
<span durImplicit="indefinite">
<span xml:id="anon2" durImplicit="indefinite">Bar</span>
</span>
<span xml:id="anon3" durImplicit="0">Baz</span>
</p>
Here, anon2 is assigned an indefinite implicit duration because its parent is an explicit span which defaults to 'par' time containment semantics. Since SMIL requires a seq container that contains an indefinite duration child to also be indefinite, then that indefinite propagates up the node tree.
This seems counterintuitive. I propose to resolve by a slight change in 10.4 from the current text:
"if the anonymous span's parent time container is a parallel time container, then the implicit duration is equivalent to the indefinite duration value as defined by [SMIL 2.1]; if the anonymous span's parent time container is a sequential time container, then the implicit duration is equivalent to zero"
to read:
"if the anonymous span's nearest explicit time container ancestor is a sequential time container, then the implicit duration is equivalent to zero; otherwise, it is equivalent to the indefinite duration value as defined by [SMIL 2.1]"
and add the following Note
"Note: An element is an explicit time container if it specifies a timeContainer attribute."
Reworking the above example with the new text, we get:
<p timeContainer="seq" durImplicit="0">
<span xml:id="anon1" durImplicit="0">Foo</span>
<span durImplicit="0">
<span xml:id="anon2" durImplicit="0">Bar</span>
</span>
<span xml:id="anon3" durImplicit="0">Baz</span>
</p>
The resolution of this issue also needs applied to TTML2.
- Related Actions Items:
- No related actions
- Related emails:
- {agenda} TTWG Meeting 4/9/2014 (from nigel.megitt@bbc.co.uk on 2014-09-03)
- ISSUE-338: inconsistent implicit duration of singleton span in sequential container [TTML 1.0] (from sysbot+tracker@w3.org on 2014-08-26)
Related notes:
Continuing the first sentence of the description:
"... is assigned indefinite, an apparent inconsistency."
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