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Merge pull request #534 from w3c/issue-0360-related-media-object-region
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Resolve definition of related media object region (#360).
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@skynavga
skynavga committed Jan 15, 2018
2 parents 31ebfbc + ddeb265 commit 18011f0
Showing 1 changed file with 40 additions and 22 deletions.
62 changes: 40 additions & 22 deletions spec/ttml2.xml
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Expand Up @@ -1384,6 +1384,34 @@ 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,
and other implementation specific properties.</p>
</note>
</def>
</gitem>
<gitem id="terms-presentation-related-element">
<label>[presentation related element]</label>
<def>
Expand Down Expand Up @@ -1484,15 +1512,8 @@ 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">
Expand All @@ -1505,7 +1526,7 @@ 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>
Expand Down Expand Up @@ -5575,10 +5596,8 @@ 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"/>, &sect;5.4.4.
This would permit, for example, the interchange of information that reflects
the semantics of <bibref ref="cta708e"/> , &sect;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
Expand Down Expand Up @@ -11553,8 +11572,7 @@ 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>
Expand Down Expand Up @@ -23322,7 +23340,7 @@ 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>
Expand All @@ -23342,12 +23360,12 @@ 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">&lt;length&gt;</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>
Expand All @@ -23365,7 +23383,7 @@ 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>
Expand Down Expand Up @@ -23434,7 +23452,7 @@ 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
Expand All @@ -23457,7 +23475,7 @@ 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
Expand Down

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