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Merged
palemieux merged 8 commits into from
Nov 14, 2017
Merged

Updated profile signaling and resolution to match TTML2 semantics #267

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dda2f98
Profile resolution now based on TTML2 profile semantics (#3)
palemieux Oct 21, 2017
d64eaff
Addressing review comments
palemieux Nov 8, 2017
5930eef
Further review comments
palemieux Nov 8, 2017
6e71e89
Rationalized document/interchange processing context
palemieux Nov 8, 2017
0dda444
Clarified mutually exclusive profile signaling
palemieux Nov 8, 2017
542859a
Accommodate optional EBU-TT-D profile signaling
palemieux Nov 9, 2017
8c1a1ea
Address feedback from 20171109
palemieux Nov 9, 2017
c91ee18
Fix grammatical nit
nigelmegitt Nov 14, 2017
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216 changes: 146 additions & 70 deletions imsc1/spec/ttml-ww-profiles.html
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Expand Up @@ -160,7 +160,9 @@ <h2>Terms and Definitions</h2>

<p><dfn>Default Region</dfn>. See Section 9.3.1 at [[!TTML2]].</p>

<p><dfn>Document Instance</dfn>. See Section 2.2 at [[!TTML2]].</p>
<p><dfn data-lt="Document Instance|Document Instances">Document Instance</dfn>. See Section 2.2 at [[!TTML2]].</p>

<p><dfn>Default Processor Profile</dfn>. As defined in [[!TTML2]].</p>

<p><dfn>Extension</dfn>. See Section 2.2 at [[!TTML2]].</p>

Expand All @@ -170,7 +172,9 @@ <h2>Terms and Definitions</h2>

<p><dfn>Document Interchange Context</dfn>. See Section 2.2 at [[!TTML2]].</p>

<p><dfn>Document Processing Context</dfn>. See Section 2.2 at [[!TTML2]].</p>
<p><dfn>Document Processing Context</dfn>. As defined in [[!TTML2]].</p>

<p><dfn>Effective Processor Profile</dfn>. As defined in [[!TTML2]].</p>

<p><dfn>Image Profile transformation processor</dfn>. A <a>transformation processor</a> that conforms to the <a>Image
Profile</a>.</p>
Expand All @@ -180,12 +184,16 @@ <h2>Terms and Definitions</h2>

<p><dfn>Linear White-Space</dfn>. See Section 2.3 at [[!TTML2]].</p>

<p><dfn>Override Content Profile</dfn>. As defined in [[!TTML2]].</p>

@nigelmegitt nigelmegitt Nov 8, 2017

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"Override Content Profile" is not defined in TTML2.

@palemieux palemieux Nov 8, 2017

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It is defined in https://github.com/w3c/ttml2/pull/468/files

@nigelmegitt nigelmegitt Nov 8, 2017

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Ah, thank you for the reminder.


<p><dfn>Processor</dfn>. Either a <a>Presentation processor</a> or a <a>Transformation processor</a>.</p>

<p><dfn>Presentation processor</dfn>. See Section 2.2 at [[!TTML2]].</p>

<p><dfn>Transformation processor</dfn>. See Section 2.2 at [[!TTML2]].</p>

<p><dfn data-lt="processor profile|processor profiles">Processor Profile</dfn>. As defined in [[!TTML2]].</p>

<p><dfn>Related Media Object</dfn>. See Section 2.2 at [[!TTML2]].</p>

<p><dfn>Related Video Object</dfn>. A <a>Related Media Object</a> that consists of a sequence of image frames, each a
Expand Down Expand Up @@ -318,23 +326,62 @@ <h3>Image Profile</h3>
<section id="profile-resolution">
<h3>Profile Resolution Semantics</h3>

<p>For the purpose of content processing, the determination of the resolved profile SHOULD take into account both the
signaled profile, as defined in <a href="#profile-signaling"></a>, and profile metadata, as designated by either (or both)
the <a>Document Interchange Context</a> or (and) the <a>Document Processing Context</a>, which MAY entail inspecting document
content.</p>
<section>
<h4>General</h4>

<p>The Profile Semantics specified in [[!TTML2]] apply.</p>

<p class="note">The default value of prohibited attributes, e.g. <code>ttp:contentProfileCombination</code>, applies.</p>

<p>If the resolved profile is not a profile supported by the <a>Processor</a> but is feasibly interoperable with the <a>Text
Profile</a>, then the resolved profile is the <a>Text Profile</a>; otherwise, if the resolved profile is not a profile
supported by the <a>Processor</a> but is feasibly interoperable with the <a>Image Profile</a>, then the resolved profile is
the <a>Image Profile</a>.</p>
<p>The <a>Text Profile</a> <a>processor profile</a> includes all of the features required by each of the following
<a>processor profiles</a>:</p>

<ul>
<li>[[ttml10-sdp-us]]</li>

<p>If the resolved profile is a profile supported by the <a>Processor</a>, then the <a>Processor</a> SHOULD process the
<a>Document Instance</a> according to the resolved profile. If the resolved profile is neither <a>Text Profile</a> nor
<a>Image Profile</a>, processing is outside the scope of this specification.</p>
<li>[[EBU-TT-D]]</li>

<li>[[ttml-imsc1.0.1]] Text Profile</li>
</ul>

<p>The <a>Image Profile</a> <a>processor profile</a> includes all of the features required by each of the following
<a>processor profiles</a>:</p>

<ul>
<li>[[ttml-imsc1.0.1]] Image Profile</li>
</ul>

<aside class="example">
The use of the <code>mimeType="application/mp4"</code> and <code>codecs="stpp.ttml.im1t"</code> attributes in a
[[MPEGDASH]] Manifest signals a track that consists of [[ttml-imsc1.0.1]] Text Profile documents. In this case the
Manifest is part of the <a>document interchange context</a>, and the <a>default processor profile</a> is extracted from
the <code>codecs</code> attribute and dereferenced via the [[ttml-profile-registry]].
</aside>
</section>

<p>If the resolved profile is undetermined or not supported by the <a>Processor</a>, then the <a>Processor</a> SHOULD
nevertheless process the <a>Document Instance</a> using one of its supported profiles, with a preference for the <a>Text
Profile</a> over the <a>Image Profile</a>; otherwise, processing MAY be aborted.</p>
<section>
<h4>Override</h4>

<p>If one or more <code>ebuttm:conformsToStandard</code> elements, as specified in [[!EBU-TT-D]], are set to any of the
following designators, then the <a>override content profile</a> SHALL be set to the profile associated with any one of the
matching designators:</p>

<ul>
<li>[[ttml-imsc1.0.1]] Text Profile Designator</li>

<li>[[ttml-imsc1.0.1]] Image Profile Designator</li>

<li>
<a>Image Profile</a> Designator
</li>

<li>
<a>Text Profile</a> Designator
</li>

<li><code>urn:ebu:tt:distribution:2014-01</code>, as specified in [[EBU-TT-D]]</li>
</ul>
</section>
</section>
</section>

Expand Down Expand Up @@ -1724,7 +1771,7 @@ <h2>Supported Features and Extensions</h2>
<tr>
<td><code>#version</code></td>

<td colspan="2">permitted</td>
<td colspan="2">prohibited</td>

@nigelmegitt nigelmegitt Nov 6, 2017

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This seems dangerous without also removing #version altogether from TTML2. What behaviour do you expect from a processor if the document does include ttp:version="2", say? It seems harsh to reject the document. I see the ednote below though.

@palemieux palemieux Nov 8, 2017

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Yes. This is a placeholder until the ttp:version semantics are clarified, or ttp:version is removed.

</tr>

<tr>
Expand Down Expand Up @@ -1866,6 +1913,9 @@ <h2>Supported Features and Extensions</h2>

<p class='note'>The <code>#linePadding</code> and <code>#multiRowAlign</code> features were erroneously not designated as
prohibited in the [[ttml-imsc1.0.1]] Image Profile.</p>

<p class="ednote">The disposition of <code>#version</code> may change upon clarification of its semantics -- see <a href=
"https://github.com/w3c/ttml2/issues/435">TTML2 issue #435</a>.</p>
</section>

<section id='common-constraints'>
Expand Down Expand Up @@ -2601,78 +2651,94 @@ <h4>itts:fillLineGap</h4>
<section id='profile-signaling'>
<h3>Profile Signaling</h3>

<section>
<section id="general-signaling">
<h4>General</h4>

<p>Unless one of the mutually exclusive scenarios specified in the following Sections apply, the
<code>ttp:contentProfiles</code> attribute SHALL be present on the <code>tt</code> element and include the designator of
the profile (either the <a>Text Profile</a> or <a>Image Profile</a>) to which the <a>Document Instance</a> conforms.</p>
<p>Unless one of the scenarios specified in Sections <a href="#imsc1-compat"></a>, <a href="#ebu-tt-d-compat"></a> or
<a href="#sdp-us-compat"></a> applies:</p>

<p class="note">The <code>ttp:contentProfiles</code> can include additional designators, beyond the Text Profile or Image
Profle designators.</p>
<ul>
<li>the <code>ttp:contentProfiles</code> attribute SHALL be present on the <code>tt</code> element and include the
profile designator (either <a>Text Profile</a> or <a>Image Profile</a>), corresponding to the profile to which the
<a>Document Instance</a> conforms;
</li>

<li>the <code>ttp:contentProfiles</code> attribute SHALL NOT simultaneously signal conformance to both <a>Image
Profile</a> and <a>Text Profile</a>;
</li>

<li>the <code>ttp:profile</code> attribute SHALL NOT be present; and</li>

<li>the <code>ttp:profile</code> element SHALL NOT be present.</li>
</ul>

<p class="note">The <code>ttp:contentProfiles</code> attribute can include additional designators, beyond those specified
herein.</p>

<p class="note">The scenarios specified in Sections <a href="#general-signaling"></a>, <a href="#imsc1-compat"></a>,
<a href="#ebu-tt-d-compat"></a> and <a href="#sdp-us-compat"></a> are intended to be mutually exclusive.</p>
</section>

<section>
<section id="imsc1-compat">
<h4>IMSC1 Compatibility</h4>

<p>If the <a>Document Instance</a> conforms to one of the profiles specified in [[ttml-imsc1.0.1]]:</p>
<p>If the <a>Document Instance</a> conforms to one of the profiles specified in [[ttml-imsc1.0.1]], and compatibility with
[[ttml-imsc1.0.1]] processors is desired:</p>

<ul>
<li>the <code>ttp:contentProfiles</code> attribute SHOULD be present on the <code>tt</code> element and include the
designator of the profile (either the <a>Text Profile</a> or <a>Image Profile</a>) to which the <a>Document Instance</a>
conforms;
<li>the <code>ttp:profile</code> attribute SHOULD be present on the <code>tt</code> element and SHALL be equal to the
designator of the [[ttml-imsc1.0.1]] profile to which the <a>Document Instance</a> conforms; and
</li>

<li>the <code>ttp:profile</code> attribute SHOULD be present on the <code>tt</code> element and equal to the designator
of the [[ttml-imsc1.0.1]] profiles to which the <a>Document Instance</a> conforms; and
</li>
<li>the <code>ttp:profile</code> element SHOULD NOT be present; and</li>

<li>the <code>ttp:profile</code> element SHOULD NOT be present.</li>
<li>the <code>ttp:contentProfiles</code> attribute SHOULD NOT be present.</li>
</ul>

<p class="note">If the <code>ttp:profile</code> attribute is not set as recommended above, the [[ttml-imsc1.0.1]] content
profile to which the <a>Document Instance</a> conforms is communicated through means outside the scope of this
specification, e.g. through the <a>document interchange context</a>.</p>

<p class="note">The use of the <code>ttp:contentProfiles</code> attribute is discouraged in this scenario to ease
differentiation between (i) <a>Document Instances</a> that are intended to be compatible with [[ttml-imsc1.0.1]]
processors, and (ii) <a>Document Instances</a> that are intended to require processors that conform to this specification
(in which case Section <a href="#general-signaling"></a> applies.)</p>
</section>

<section>
<section id="ebu-tt-d-compat">
<h4>EBU-TT-D Compatibility</h4>

<p>If the <a>Document Instance</a> conforms to both [[ttml-imsc1.0.1]] and [[EBU-TT-D]]:</p>
<p>If the <a>Document Instance</a> conforms to both [[ttml-imsc1.0.1]] and [[EBU-TT-D]], and compatibility with
[[EBU-TT-D]] processors is desired:</p>

<ul>
<li>neither the <code>ttp:profile</code> attribute nor the <code>ttp:profile</code> element are present;</li>

<li>the <code>ebuttm:conformsToStandard</code> element as specified in [[!EBU-TT-D]] and illustrated in <a href=
"#ebu-tt-d-interop"></a> SHOULD include:
<li>the <code>ttp:profile</code> attribute is not present;</li>

<ul>
<li>the designator of the [ttml-imsc1.0.1]] profile to which the <a>Document Instance</a> conforms;
</li>
<li>the <code>ttp:contentProfiles</code> attribute is not present;</li>

<li>the designator of the profile (either the <a>Text Profile</a> or <a>Image Profile</a>) to which the <a>Document
Instance</a> conforms;
</li>

<li>the URI <code>"urn:ebu:tt:distribution:2014-01"</code></li>
</ul>
</li>

<li>the <code>ttp:profile</code> and <code>ebuttm:conformsToStandard</code> elements SHALL NOT signal conformance to both
<a>Image Profile</a> and <a>Text Profile</a> in a given <a>Document Instance</a>.
<li>one <code>ebuttm:conformsToStandard</code> element, as specified in [[!EBU-TT-D]] and illustrated in <a href=
"#ebu-tt-d-interop"></a>, SHOULD be set to the [[ttml-imsc1.0.1]] profile designator corresponding to the profile to
which the <a>Document Instance</a> conforms;
</li>
</ul>

<p class="note">If <code>ebuttm:conformsToStandard</code> elements signal neither [[ttml-imsc1.0.1]] nor [[!EBU-TT-D]]
profile conformance, the <a>Document Instance</a> conforms is communicated through means outside the scope of this
specification, e.g. through the <a>document interchange context</a>.</p>
</section>

<section>
<section id="sdp-us-compat">
<h4>SDP-US Compatibility</h4>

<p>If the <a>Document Instance</a> conforms to both [[ttml-imsc1.0.1]] and [[ttml10-sdp-us]]:</p>
<p>If the <a>Document Instance</a> conforms to both [[ttml-imsc1.0.1]] and [[ttml10-sdp-us]], and compatibility with
[[ttml10-sdp-us]] processors is desired:</p>

<ul>
<li>the <code>ttp:contentProfiles</code> attribute SHOULD be present on the <code>tt</code> element and include the
designator of the profile (either the <a>Text Profile</a> or <a>Image Profile</a>) to which the <a>Document Instance</a>
conforms;
</li>
<li>the <code>ttp:profile</code> attribute is not present;</li>

<li>the <code>ttp:contentProfiles</code> attribute is not present;</li>

<li>the <code>ttp:profile</code> attribute is not present and the <code>ttp:profile</code> element is present, as
illustrated in <a href="#sdp-us-interop"></a>.
<li>the <code>ttp:profile</code> element is present, as illustrated in <a href="#sdp-us-interop"></a>.
</li>
</ul>
</section>
Expand Down Expand Up @@ -2829,11 +2895,6 @@ <h3>Profile Designator</h3>
</tr>
</tbody>
</table>

<p class='note'>As specified in <a href="#profile-signaling"></a>, the presence of the <code>ttp:profile</code> attribute is
not required by this profile. The profile designator specified above is intended to be generally used to signal conformance
of a <a>Document Instance</a> to the profile. The details of such signaling depends on the application, and can, for
instance, use metadata structures out-of-band of the <a>Document Instance</a>.</p>
</section>

<section id='recommended-char-sets'>
Expand Down Expand Up @@ -3001,11 +3062,6 @@ <h3>Profile Designator</h3>
</tr>
</tbody>
</table>

<p class='note'>As specified in <a href="#profile-signaling"></a>, the presence of the <code>ttp:profile</code> attribute is
not required by this profile. The profile designator specified above is intended to be generally used to signal conformance
of a <a>Document Instance</a> to the profile. The details of such signaling depends on the application, and can, for
instance, use metadata structures out-of-band of the <a>Document Instance</a>.</p>
</section>

<section>
Expand Down Expand Up @@ -4304,7 +4360,8 @@ <h3>SMPTE-TT (SMPTE ST 2052-1)</h3>

<li>when the designator <code>"http://www.smpte-ra.org/schemas/2052-1/2010/profiles/smpte-tt-full"</code> is used as a
value for <code>ttp:profile</code> element or attribute (see Section 5.8 at [[!SMPTE2052-1]]), Text Profile or Image
Profile is signaled by the Document Interchange Context and/or the Document Processing Context.</li>
Profile is signaled by the <a>Document Interchange Context</a> and/or the <a>Document Processing Context</a>.
</li>
</ul>

<p>The following is an example of a document that conforms to both Text Profile and [[!SMPTE2052-1]]:</p>
Expand Down Expand Up @@ -4417,6 +4474,25 @@ <h4>Reference to TTML2</h4>
<p>Replaced normative references to [[TTML1]] with normative references to [[TTML2]].</p>
</section>

<section class='appendix'>
<h4>Profile resolution semantics</h4>

<p>Section <a href="#profile-resolution"></a> is now based on [[TTML2]] Profile Semantics.</p>
</section>

<section class='appendix'>
<h4>Profile signaling</h4>

<p>Section <a href="#profile-signaling"></a> adds support for signaling of the profiles specified herein.</p>
</section>

<section class='appendix'>
<h4>Profile designators</h4>

<p>Profile designators introduced for each of the profiles specified herein. See Sections <a href=
"#text-profile-designator"></a> and <a href="#image-profile-designator"></a>.</p>
</section>

<section class='appendix'>
<h4>Added Features</h4>

Expand Down