Add clipBegin and clipEnd parameter attributes #486
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#483 Semantics defined but ISD generation algorithm not updated yet because there’s an issue note there saying that it needs to be revised for other reasons. I’ve added a similar note for #483 to include the ISD pruning/truncation/extension semantics when that is done. Also added to schemas and regenerated ED.
clipEnd should not be called clipBegin where it isn't supposed to be.
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What problem is this intended to solve? It is not clear from #483 |
| <p>When revising, also include truncation/pruning/extension to deal with the | ||
| <loc href="#parameter-attribute-clipBegin">ttp:clipBegin</loc> and | ||
| <loc href="#parameter-attribute-clipEnd">ttp:clipEnd</loc> semantics.</p> | ||
| </issue> |
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clipBegin and clipEnd should be authorial hints only and not affect processing. More specifically, it is not clear why they need to affect processing since the application already controls presentation of the document, including starting and stopping presentation/processing at timeline locations outside of ISD boundaries.
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I disagree. This needs to be normative and to affect processing. It has no effect when the attributes are absent, so it has no backward compatibility issue.
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You have simply not motivated at all whatsoever why the processing model needs to be modified. The TTWG really needs to stop modifying TTML2 unless necessary.
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Yes, I have, at https://github.com/w3c/ttml2/issues/483#issuecomment-345283633 perhaps you did not spot that?
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@palemieux ping?
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@nigelmegitt Thanks for the reminder. See additional thoughts in the ticket. For the record, you have not (yet) convinced me that creating additional ISDs is necessary.
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Why would one want to author a document and then say that only part of the document applies? Clip begin and end sound a lot like query parameters one might find on an HTTP request on a media resource where one is asking the server to deliver a segment from a larger resource. It doesn't make sense to me to put such parameters into the larger resource, which is what you are asking for here.
@skynavga They're nothing to do with query parameters. See the issue for the use case and motivation - in summary it's about the ability for a document author to define the temporal period during which the document defines behaviour. If the parameter attribute names seem misleading, could you please propose alternative names? |
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In order to make progress on TTML2, in the absence of a clear consensus, I'm closing this pull request, which can be reopened or moved to another repo if we want to pick it up again in the future. |
Closes #483.
Semantics defined but ISD generation algorithm not updated yet
because there’s an issue note there saying that it needs to be revised
for other reasons. I’ve added a similar note for #483 to include the
ISD pruning/truncation/extension semantics when that is done.
Also added to schemas and regenerated ED.