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Resolve definition of related media object region (#360). #534
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@@ -1380,6 +1380,34 @@ possible determinations of a <loc href="#terms-processor-profile">processor prof | |
<p>See definition of <loc href="#root-container-region-semantics-par">PAR</loc>.</p> | ||
</def> | ||
</gitem> | ||
<gitem id="terms-presentation-context"> | ||
<label>[presentation context]</label> | ||
<def> | ||
<p>See <loc href="#terms-presentation-processing-context">presentation processing context</loc>.</p> | ||
</def> | ||
</gitem> | ||
<gitem id="terms-presentation-processing-context"> | ||
<label>[presentation processing context]</label> | ||
<def> | ||
<p>A hypothetical display device on which the <loc href="#terms-root-container-region">root container region</loc> and a | ||
<loc href="#terms-related-media-object-region">related media object region</loc> are presented.</p> | ||
</def> | ||
</gitem> | ||
<gitem id="terms-presentation-context-coordinate-space"> | ||
<label>[presentation context coordinate space]</label> | ||
<def> | ||
<p>The coordinate space associated with the <loc href="#terms-presentation-context">presentation context</loc>.</p> | ||
<note role="clarification"> | ||
<p>For a given implementation of a <loc href="#terms-presentation-processor">presentation processor</loc>, | ||
it is possible that <emph>display pixels</emph> associated with <emph>logical pixels</emph> in the | ||
<loc href="#terms-document-coordinate-space">document coordinate space</loc> correspond exactly with | ||
<emph>presentation pixels</emph> in the <loc href="#terms-presentation-context-coordinate-space">presentation context coordinate space</loc>; | ||
however, such an exact correspondence need not apply, and, in particular, the (implementation defined) mapping between these coordinate spaces | ||
may be subject to a transformation of pixel aspect ratios, resolutions, color spaces, color sample depths, | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Probably need an "etc." on this list - I'm thinking of gamma and pixel layout for example, but the list probably isn't worth describing fully, even if that were possible. There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. agree, will add "etc" There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. fixed |
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and other implementation specific properties.</p> | ||
</note> | ||
</def> | ||
</gitem> | ||
<gitem id="terms-presentation-related-element"> | ||
<label>[presentation related element]</label> | ||
<def> | ||
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@@ -1480,15 +1508,8 @@ information, and with which that <loc href="#terms-document-instance">document i | |
<gitem id="terms-related-media-object-region"> | ||
<label>[related media object region]</label> | ||
<def> | ||
<p>When a non-null <loc href="#terms-related-media-object">related media object</loc> exists, the region of this media object, | ||
expressed in the coordinate system that applies to the <loc href="#terms-document-instance">document instance</loc> that is associated with the | ||
related media object.</p> | ||
<issue id="issue-ttml2-360"> | ||
<head>Update Definition of Related Media Object Region</head> | ||
<source><loc href="https://github.com/w3c/ttml2/issues/360">https://github.com/w3c/ttml2/issues/360</loc></source> | ||
<p>Untangle definition from use of document coordinate space.</p> | ||
</issue> | ||
<p></p> | ||
<p>A region of the <loc href="#terms-presentation-processing-context">presentation processing context</loc> where a non-null, visual | ||
<loc href="#terms-related-media-object">related media object</loc> is presented.</p> | ||
</def> | ||
</gitem> | ||
<gitem id="terms-relative-dimension"> | ||
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@@ -1501,7 +1522,7 @@ the applicable writing mode.</p> | |
<gitem id="terms-root-container-region"> | ||
<label>[root container region]</label> | ||
<def> | ||
<p>A unique, logical region that establishes a coordinate system into which | ||
<p>A unique, logical, rectangular region that establishes a coordinate system into which | ||
<loc href="#terms-content-region">content regions</loc> are placed and optionally clipped, | ||
about which see also <specref ref="root-container-region-semantics"/>.</p> | ||
</def> | ||
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@@ -5578,10 +5599,8 @@ that the <loc href="#terms-document-processing-context">document processing cont | |
</note> | ||
<note role="elaboration"> | ||
<p>If an author desires to signal the (storage or image) aspect ratio of the <loc href="#terms-root-container-region">root container region</loc> | ||
without specifying its resolution, then this may be accomplished by using metadata specified | ||
in an external namespace, such as <att>m708:aspectRatio</att> as defined in <bibref ref="smpte2052-11"/>, §5.4.4. | ||
This would permit, for example, the interchange of information that reflects | ||
the semantics of <bibref ref="cta708e"/> , §4.5 “Caption Service Metadata”, “ASPECT RATIO”.</p> | ||
without specifying its resolution, then this may be accomplished by using | ||
the <loc href="#parameter-attribute-displayAspectRatio"><att>ttp:displayAspectRato</att></loc> parameter attribute.</p> | ||
</note> | ||
<p>Except for the <att>tts:extent</att> attribute described above, an attribute in the TT Style Namespace should not | ||
be specified on the <el>tt</el> element unless it denotes an inheritable style property, in which case such inheritable style property is available | ||
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@@ -11678,8 +11697,7 @@ content rectangles (boxes) are coterminous.</p> | |
<p>If a horizontal or vertical position offset is specified by a <att>tts:position</att> attribute in the form of a scalar value | ||
on a <loc href="#document-structure-vocabulary-tt"><el>tt</el></loc> element, then that value must be expressed using pixel (<code>px</code>) units, | ||
in which case a pixel must be interpreted as a pixel in the | ||
<!-- FIXME <loc href="#terms-presentation-context-coordinate-space">presentation context coordinate space</loc>--> | ||
presentation context coordinate space | ||
<loc href="#terms-presentation-context-coordinate-space">presentation context coordinate space</loc> | ||
(and not a pixel in the <loc href="#terms-document-coordinate-space">document coordinate space</loc>).</p> | ||
<p>If a computed value of the property associated with this attribute is not supported, | ||
then a <loc href="#terms-presentation-processor">presentation processor</loc> must use the closest supported value.</p> | ||
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@@ -24013,7 +24031,7 @@ it requires support for the | |
<loc href="#document-structure-vocabulary-tt"><el>tt</el></loc> element or is inferred using other information as described below.</p> | ||
<note role="elaboration"> | ||
<p>The actual, physical presentation of the pixels of the root container may be subject to numerous transformations in | ||
aspect ratio, sample resolution, and color space subsequent to all defined TTML presentation processing. Such post-TTML | ||
aspect ratio, sample resolution, and color space subsequent to defined TTML presentation processing. Such post-TTML | ||
processing is wholly out of scope of this specification.</p> | ||
</note> | ||
</def> | ||
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@@ -24033,12 +24051,12 @@ it requires support for the | |
<item><p>if the value of the <loc href="#style-attribute-extent">tts:extent</loc> attribute consists of | ||
two pixel-valued <loc href="#style-value-length"><length></loc> expressions, the storage aspect ratio is considered | ||
to be specified and having a numeric value equal to the | ||
<loc href="#terms-width">width</loc> of the extent divided its <loc href="#terms-height">height</loc>;</p></item> | ||
<loc href="#terms-width">width</loc> of the extent divided by its <loc href="#terms-height">height</loc>;</p></item> | ||
<item><p>otherwise (the computed value is <code>contain</code>), | ||
the storage aspect ratio is considered to be unspecified and is inferred using other information described below.</p></item> | ||
</olist> | ||
<note role="elaboration"> | ||
<p>On its own, a logical pixel has no intrinsic aspect ratio; however, when mapped to a display pixel, it assumes the fixed aspect ratio | ||
<p>On its own, a logical pixel has no intrinsic aspect ratio; however, when mapped to a display pixel, it assumes the fixed value | ||
defined by the pixel aspect ratio of the root container as specified below.</p> | ||
</note> | ||
</def> | ||
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@@ -24056,7 +24074,7 @@ it requires support for the | |
</def> | ||
</gitem> | ||
</glist> | ||
<p>The following sub-sections specify how these aspect ratios are resolved according to which are specified in a document.</p> | ||
<p>The following sub-sections specify how these aspect ratios are resolved according to which (ratios) are specified in a document.</p> | ||
<div3 id="root-container-region-semantics-0-aspect-ratio"> | ||
<head>No Aspect Ratio</head> | ||
<p>If none of the three aspect ratios is specified, then the three aspect ratios are determined according to the following ordered steps:</p> | ||
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@@ -24126,7 +24144,7 @@ the number of columns signifies the resolution of the root container region on t | |
the number of rows signifies the resolution of the root container region on the <loc href="#terms-vertical-axis">vertical axis</loc>, where the | ||
former is defined to be the <loc href="#terms-width">width</loc> and the | ||
latter is defined to be the <loc href="#terms-height">height</loc> of the root container region, respectively, | ||
and where the collection of resolutions along both axes is referred to as the | ||
and where the collection of (these two) resolutions along both axes is referred to as the | ||
<emph>collective resolution</emph> (or <emph>spatial extent</emph>) of the root container region.</p> | ||
<p>If the value of the <loc href="#style-attribute-extent">tts:extent</loc> attribute | ||
is specified on the <loc href="#document-structure-vocabulary-tt"><el>tt</el></loc> element and consists of | ||
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@@ -24149,7 +24167,7 @@ in order to assign a logical resolution that preserves that same precision.</p> | |
<head>Coordinate Space</head> | ||
<p>The coordinate space of the root container region, also known as the <loc href="#terms-document-coordinate-space">document coordinate space</loc>, | ||
is an unbounded, two-dimensional plane on which a closed set of logical pixels are defined that take the form of a rectangle <emph>R</emph> such that | ||
the said pixels are interior to (inside of) <emph>R</emph>, and where the origin (position) of this coordinate space is coincident with the upper, | ||
the said pixels are interior to (inside of) the boundary of <emph>R</emph>, and where the origin (position) of this coordinate space is coincident with the upper, | ||
left-hand corner of <emph>R</emph>, and where positive pixels on the vertical axis extend downwards and positive pixels on the horizontal axis | ||
extend rightwards. | ||
Furthermore, the <loc href="#terms-width">width</loc> and <loc href="#terms-height">height</loc> of <emph>R</emph> is set to the | ||
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Why must there be a non-null related media object? It would be reasonable to have a visual presentation processing context used to present captions against an audio only related media object for example, which would therefore be absent from the presentation context, assuming the presentation context is visual.
Of course it is also possible to present a TTML document in a presentation context with no related media object at all.
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agreed, can allow non-visual or null RMOs
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fixed