TTML/changeProposal001

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Amendments to the set Attribute - CLOSED

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

Issues Addressed

Issue 165 - Animate multiple styles with 'set' element - Closed - [1].

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

None (that are not noted by Editorial Notes).

Edits applied

See Issues Addressed section above.

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