No warning for `tts:origin` and `tts:extent` attributes on `<p>` elements

[marcushaas-bbc]

Given the XML fragment:

<p begin="00:00:35:21" end="00:00:38:15" region="pop1" style="basic" tts:origin="39.59% 80.13%" tts:extent="20.82% 9.87%">Some cubes of ice,</p>
<p begin="00:00:35:21" end="00:00:38:15" region="pop2" style="basic" tts:origin="39.59% 80.13%" tts:extent="20.82% 9.87%">a set of dice</p>

where two different lines of text are specified to be displayed at the same time, the playback effect is that the second subtitle is displayed over the first, ie the second subtitle overlaps the first, usually obscuring it entirely.

The validator does signal there is a general problem without giving the location (unless the -collate_more_than option is set), in this case:

Fail,ebuttd_overlapping_region_constraint,12 locations,Elements overlap spatially and temporally

The XML specifies these lines are to be displayed in different regions ("pop1", "pop2"), but in this example those regions have no positioning attributes, only styling:

<layout>
            <region xml:id="pop1" tts:backgroundColor="transparent" tts:showBackground="whenActive"/>
            <region xml:id="pop2" tts:backgroundColor="transparent" tts:showBackground="whenActive"/>
            <region xml:id="pop3" tts:backgroundColor="transparent" tts:showBackground="whenActive"/>
            <region xml:id="pop4" tts:backgroundColor="transparent" tts:showBackground="whenActive"
</layout>

The validator warns of this:

Fail,ebuttd_region_attributes_constraint,region element xml:id pop1,Required style attribute {http://www.w3.org/ns/ttml#styling}origin missing from region element
Fail,ebuttd_region_attributes_constraint,region element xml:id pop1,Required style attribute {http://www.w3.org/ns/ttml#styling}extent missing from region element

Positioning data is presented in the XML as tts:origin and tts:extent attributes on the <p> elements, but this is invalid in EBU-TT-D and is not flagged by the validator.

XML file:

p07y898m-a0b5f41e-f4d2-45a5-9f27-f5f166ff4803.xml

Validator file:

p07y898m-a0b5f41e-f4d2-45a5-9f27-f5f166ff4803.csv

[nigelmegitt]

The core issue I see here is that the tts:origin and tts:extent attributes should not be on <p> elements in EBU-TT-D, but this isn't picked up.