TTML/changeProposal001

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Amendments to the set Attribute - OPEN

  • Owner: Jerry Smith.
  • Started: April 18, 2012.

Issues to be addressed

Issue 165 - done

Summary

When using the set element to model pop on type captioning, it is typical to need to change a number of styles at once; for example position, extent and display. Currently this requires one set element for each attribute. Furthermore it is often the case that a number of these style groups are repeated. In addition it is common to discover the need for such animation during caption generation when making the text container. Currently this requires duplicating the timing using <set> elements on the region, this is inefficient both for authoring and subsequent rendering as the timing tree is effectively doubled.

The proposal is to update <set> to allow:

  • more than one style attribute to be animated simultaneously.

<set begin='00:00:09.000' end='00:00:09.500' s:origin='10% 20%' s:display='auto' />

  • animating a whole block of styles using a style reference:

<set begin='00:00:09.000' end='00:00:09.500' style='animationStyles01' />

  • to animate a referenced element (adopted from SMIL
   <p region="region1" begin='00:00:09.000' end='00:00:09.500'>
      <set targetElement="region1" s:origin='10% 20%' s:extent='80% 20%' />
      Caption Text in moved region
    </p>

Edits awaiting application

Animation attributes

Add a new class to table: Table 5 – Attribute Vocabulary

Animation Attributes targetElement

global replace

Any animation elements specified by children in the Animation.class element group apply semantically to the xxx element.

with

Any animation elements specified by children in the Animation.class element group apply semantically to the parent element unless overriden using a targetElement attribute


Rewrite 11.1.1 As follows

11.1.1 set

The set element is used as a child element of a content element or a region element in order to express a discrete change of one or more style parameter values that applies over some time interval either on the parent element, or alternately on some element referenced using the targetElement attribute.

The set element accepts as its children zero or more elements in the Metadata.class element group.

XML Representation – Element Information Item: set

<set
  begin = <timeExpression>
  dur = <timeExpression>
  end = <timeExpression>
  xml:id = ID
  xml:lang = string
  xml:space = (default|preserve)
  targetElement = IDREF
  style = IDREFS
  {any attribute in TT Style namespace}
  {any attribute not in default or any TT namespace}>
  Content: Metadata.class*
</set>

rewrite 11.2 Animation Attribute Vocabulary

This section defines the following basic animation attributes for use with Animation.class elements:

11.2.1 targetElement

11.2.1 targetElement The targetElement attribute specifies the target element to be animated. The attribute value must be the value of an XML identifier attribute of an element (i.e. an "IDREF") within the host document. If this attribute is omitted the target element is the parent element of the set. If the target element is not temporally active during the animation period no animated change is made.

The simultaneous use of the style attributes and inline styles is permitted, the values of the Specified Style Set of the set element is applied to the like attributes of the target element during the animated period

Update 8.2.1 style section

Add <set> to the enumerated list.

Schemas

Update schemas as appropriate.

Add Feature D.1.1.1 #animation-target

A TTML transformation processor supports the #animation-target feature if it recognizes and is capable of transforming the following vocabulary defined by 11.2.1 targetElement:

targetElement A TTML presentation processor supports the #animation-target feature if it implements presentation semantic support for the same vocabulary enumerated above.

Add Feature D.1.1.2 #animation-block

A TTML transformation processor supports the #animation-block feature if it recognizes and is capable of transforming the following vocabulary defined by 8 Styling: when present on the set element:

style

A TTML presentation processor supports the #animation-block feature if it implements presentation semantic support for the same vocabulary enumerated above.

Edits applied

Impact

  • Allows the set element to be used more effectively during caption authoring, especially during translation from linear formats such as CEA 608.
  • Some Authors have attempted to animate origin position and extent using style attributes directly on the content elements. This is a formal way of obtaining the expected behaviour, but avoiding the erroneous content.
  • Improves efficiency by minimising the number of active timing elements


References

SMIL animation