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Add syntax of codecs parameter #78

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merged 5 commits into from
Sep 16, 2020
Merged

Add syntax of codecs parameter #78

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20d7bed
Add syntax of codecs parameter
nigelmegitt Sep 2, 2020
99619ca
Add note about MP4 codecs parameter
nigelmegitt Sep 2, 2020
f3cf734
Address review comments
nigelmegitt Sep 3, 2020
54b66e6
Prohibit `"."` from `element`
nigelmegitt Sep 3, 2020
a88760d
Add concrete example note
nigelmegitt Sep 3, 2020
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79 changes: 68 additions & 11 deletions index.html
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Original file line number Diff line number Diff line change
Expand Up @@ -105,6 +105,23 @@
// !!!! IMPORTANT !!!! MAKE THE ABOVE BLINK IN YOUR HEAD
};
</script>
<style>
table.coldividers td + td { border-left:1px solid gray; text-align: center;}
table.syntax { border: 0px solid black; width: 85%; border-collapse: collapse }
table.syntax caption { font-weight: bold; text-align: left; padding-bottom: 0.5em }
table.syntax th { border: 0px solid black; text-align: left }
table.syntax td { border: 0px solid black }
table.syntax div { background-color: #ffffc8 }
div.exampleInner { background-color: #d5dee3;
border-top-width: 4px;
border-top-style: double;
border-top-color: #d3d3d3;
border-bottom-width: 4px;
border-bottom-style: double;
border-bottom-color: #d3d3d3;
padding: 4px; margin: 0em }

</style>
</head>
<body>
<section id="abstract">
Expand All @@ -123,8 +140,9 @@ <h2>Abstract</h2>
of inline profile definitions) is not considered to be an identifiable,
shared profile definition, but rather, a private profile definition
scoped to the document instance in which it is defined.</p>
</section>
<section id="sotd"></section>

</section> <!-- abstract -->
<section id="sotd"></section> <!-- sotd -->
<section id="purpose" class="informative">
<h2>Purpose</h2>
<p>This document serves two purposes: (1) to define the Media Type
Expand Down Expand Up @@ -152,7 +170,35 @@ <h2>Purpose</h2>
specifications) actually used in the resource.</p>
</div>
<p>Applications using the entries in this registry are encouraged to support
values of the <code>codecs</code> parameter that
the <code>codecs</code> parameter.</p>
<p>The <code>codecs</code> parameter value syntax is defined as
<code>codecs-parameter-value</code> as follows,
expressed using the syntax expression conventions defined by §2.3 of [[TTML2-1e]].</p>
<table class="syntax">
<tbody>
<tr>
<td>
<div class="exampleInner">
<pre class="nohighlight">
identifier
: element // element defined by [RFC6381]
// where "+", "|" and "." are prohibited characters
// ("." is reserved as a hierarchy delimiter in [RFC6381])

and-group
: identifier ["+" identifier]* // no linear white-space is implied or permitted
// between each token

codecs-parameter-value
: and-group ["|" and-group]* // no linear white-space is implied or permitted
// between each token
</pre>
</div>
</td>
</tr>
</tbody>
</table>
<p>The <code>codecs</code> parameter may
employ either (or both) of two combination operators, <code>+</code> (AND) and <code>|</code> (OR), which may be
used to specify, respectively, that all processor profiles apply
(simultaneously) or that any processor profile of a list of profiles may
Expand All @@ -171,14 +217,25 @@ <h2>Purpose</h2>
both operators in a <code>codecs</code> value expression will
need to process such combination semantics as a higher level
protocol outside the scope of [[TTML2-1e]] semantics.</p>
<p class="note">The example <code>A+B|C+D|E</code> specifies that a TTML processor that implements
<p class="note">The example <code>A+B|C+D|E</code> specifies that a TTML processor that implements
any one of the <code>A+B</code> or <code>C+D</code> or <code>E</code> processor profiles satisfies
the requirements to fetch and begin decode/processing of a TTML
document, where <code>X+Y</code> means that both <code>X</code> and <code>Y</code> processor profiles must be
supported, and <code>X|Y</code> means that either <code>X</code> or <code>Y</code> processor profile must be
supported.</p>
<p></p>
</section>
<p class="note">For example,
the <code>codecs</code> string for specifying either a TTML processor that supports
[[IMSC1.0.1]] Text Profile or one that supports [[EBU-TT-D-1]]
would be `"im1t|etd1"`.
The <code>codecs</code> string for specifying a TTML processor that supports
the union of sets of required features of both
[[IMSC1.0.1]] Text Profile and [[EBU-TT-D-1]]
would be `"im1t+etd1"`.</p>
<p class="note">Another <code>codecs</code> parameter is defined by
[[RFC6381]] for application/mp4 (ISO BMFF) and
extended for TTML by [[iso14496-30]].</p>
<p></p>
</section> <!-- purpose -->
<section id="mediatype" class="normative">
<h2>Media Type Registration</h2>
<p>This section defines the media type "application/ttml+xml",
Expand Down Expand Up @@ -363,7 +420,7 @@ <h2>Media Type Registration</h2>
<p>The W3C has change control over this specification.</p>
</dd>
</dl>
</section>
</section> <!-- mediatype -->
<section id="Registration_Entry_Requirements_and_Update_Process" class="normative">
<h2>Registration Entry Requirements and Update Process</h2>
<ol>
Expand All @@ -372,7 +429,7 @@ <h2>Registration Entry Requirements and Update Process</h2>
this registry. An identifier must conform with
the <code>element</code> non-terminal of [[!RFC6381]]
and, furthermore, may not contain any of the characters in the regular
expression character class <code>[+|]</code>.</p>
expression character class <code>[+|.]</code>.</p>
<div class="note">
<p>As a consequence of the above syntactic constraints,
the value space of the <code>codecs</code> parameter described
Expand Down Expand Up @@ -405,7 +462,7 @@ <h2>Registration Entry Requirements and Update Process</h2>
deleted, there is no intent to re-use deleted profile
values. That is, the intent is that profile entries are
"stable".</p>
</section>
</section> <!-- Registration_Entry_Requirements_and_Update_Process -->
<section id="registry" class="normative">
<h2>Registry</h2>
<p>This section is the registry of short form profile
Expand Down Expand Up @@ -658,7 +715,7 @@ <h2>Profile designator and specifications</h2>
</tr>
</tbody>
</table>
</section>
</section>
</section> <!-- registry-profile-designator-specifications -->
</section> <!-- registry -->
</body>
</html>