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Add MediaTranscripts to MediaMetadata (#370) #371

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ac4010f
Add MediaTranscripts to MediaMetadata (#370)
yrw-google Mar 25, 2026
f72e2e9
Update MediaTranscript to be a dictionary
yrw-google Apr 2, 2026
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279 changes: 277 additions & 2 deletions index.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -1090,6 +1090,7 @@ interface MediaMetadata {
attribute DOMString album;
attribute FrozenArray<object> artwork;
[SameObject] readonly attribute FrozenArray<ChapterInformation> chapterInfo;
[SameObject] readonly attribute FrozenArray<MediaTranscripts> transcripts;
};

dictionary MediaMetadataInit {
Expand All @@ -1098,6 +1099,7 @@ dictionary MediaMetadataInit {
DOMString album = "";
sequence<MediaImage> artwork = [];
sequence<ChapterInformationInit> chapterInfo = [];
sequence<MediaTranscriptsInit> transcripts = [];
};
</pre>

Expand Down Expand Up @@ -1131,6 +1133,11 @@ dictionary MediaMetadataInit {
chapter information</dfn>.
</p>

<p>
A {{MediaMetadata}} has an associated list of <dfn for="MediaMetadata">
transcripts</dfn>.
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</p>

<p>
A {{MediaMetadata}} is said to be an <dfn>empty metadata</dfn> if it is equal
to `null` or all the following conditions are true:
Expand All @@ -1143,6 +1150,7 @@ dictionary MediaMetadataInit {
is <code>0</code>.</li>
<li>Its <a for=MediaMetadata>chapter information</a> length is
<code>0</code>.</li>
<li>Its <a for=MediaMetadata>transcripts</a> length is <code>0</code>.</li>
</ul>

<p>
Expand Down Expand Up @@ -1185,6 +1193,19 @@ dictionary MediaMetadataInit {
to the result of [=Create a frozen array|creating a frozen array=] from
<var>chapters</var>.
</li>
<li>
Let <var>transcripts</var> be an empty list of type {{MediaTranscripts}}.
</li>
<li>
For each <var>entry</var> in <var>init</var>'s
{{MediaMetadataInit/transcripts}}, [=create a MediaTranscripts=] from
<var>entry</var> and append it to <var>transcripts</var>.
</li>
<li>
Set <var>metadata</var>'s <a for="MediaMetadata">transcripts</a>
to the result of [=Create a frozen array|creating a frozen array=] from
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<var>transcripts</var>.
</li>
<li>
Return <var>metadata</var>.
</li>
Expand Down Expand Up @@ -1319,10 +1340,29 @@ user agent MUST run the following steps:
</li>
</ol>

<p>
The <dfn attribute for="MediaMetadata">chapterInfo</dfn> attribute reflects
the {{MediaMetadata}}'s <a for=MediaMetadata>chapter information</a>.
On getting, it MUST return the {{MediaMetadata}}'s
<a for=MediaMetadata>chapter information</a>. On setting, it MUST set the
{{MediaMetadata}}'s <a for=MediaMetadata>chapter information</a> to the given
value.
</p>

<p>
The <dfn attribute for="MediaMetadata">transcripts</dfn> attribute reflects
the {{MediaMetadata}}'s <a for=MediaMetadata>transcripts</a>. On getting,
it MUST return the {{MediaMetadata}}'s <a for=MediaMetadata>transcripts</a>.
On setting, it MUST set the {{MediaMetadata}}'s
<a for=MediaMetadata>transcripts</a> to the given value.
</p>

<p>
When {{MediaMetadata}}'s <a for=MediaMetadata>title</a>, <a
for=MediaMetadata>artist</a>, <a for=MediaMetadata>album</a> or <a
for=MediaMetadata>artwork images</a> are modified, the user agent MUST run the
for=MediaMetadata>artist</a>, <a for=MediaMetadata>album</a>,
<a for=MediaMetadata>artwork images</a>,
<a for=MediaMetadata>chapter information</a> or
<a for=MediaMetadata>transcripts</a> are modified, the user agent MUST run the
following steps:
</p>
<ol>
Expand Down Expand Up @@ -1482,6 +1522,241 @@ used to specify the {{MediaImage}} object's <a>MIME type</a>. It is a hint as to
the media type of the image. The purpose of this attribute is to allow a user
agent to ignore images of media types it does not support.

<h2 id="the-media-transcripts-interface">The {{MediaTranscripts}} interface</h2>

<pre class="idl">
[Exposed=Window]
interface MediaTranscripts {
readonly attribute DOMString language;
[SameObject] readonly attribute FrozenArray&lt;MediaTranscript> transcripts;
};

dictionary MediaTranscriptsInit {
DOMString language = "en-US";
sequence&lt;MediaTranscript> transcripts = [];
};
</pre>

<p>
A {{MediaTranscripts}} object is a representation of transcripts for a
language, which can be used by user agents to provide transcription for the
media content.
</p>

<p>
A {{MediaTranscripts}} has an associated
<dfn for="MediaTranscripts">language</dfn> which is DOMString of a BCP 47
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language tag.
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</p>

<p>
A {{MediaTranscripts}} has an associated list of
<dfn for="MediaTranscripts">transcripts</dfn> for the language.
</p>

<p>
To <dfn>create a {{MediaTranscripts}}</dfn> with <var>init</var>, run the
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following steps:
</p>
<ol>
<li>
Let <var>transcripts</var> be a new {{MediaTranscripts}} object.
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</li>
<li>
If <var>init</var>'s {{MediaTranscripts/language}} is not a valid BCP 47
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language tag, throw a <a exception>TypeError</a> and abort these steps.
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</li>
<li>
Set <var>transcripts</var>'s {{MediaTranscripts/language}} to
<var>init</var>'s {{MediaTranscripts/language}}.
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</li>
<li>
Let <var>transcriptList</var> be an empty list of type {{MediaTranscript}}.
</li>
<li>
For each <var>entry</var> in <var>init</var>'s
{{MediaTranscriptsInit/transcripts}}, [=create a MediaTranscript=] from
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<var>entry</var> and append it to <var>transcriptList</var>.
</li>
<li>
Set <var>transcripts</var>'s <a for="MediaTranscripts">transcripts</a> to
the result of [=Create a frozen array|creating a frozen array=] from
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<var>transcriptList</var>.
</li>
<li>
Return <var>transcripts</var>.
</li>
</ol>

<p>
The <dfn attribute for="MediaTranscripts">language</dfn> attribute reflects
the {{MediaTranscripts}}'s <a for=MediaTranscripts>language</a>. On getting,
it MUST return the {{MediaTranscripts}}'s
<a for=MediaTranscripts>language</a>.
</p>

<p>
The <dfn attribute for="MediaTranscripts">transcripts</dfn> attribute
reflects the {{MediaTranscripts}}'s <a for="MediaTranscripts">transcripts</a>.
On getting, it MUST return the {{MediaTranscripts}}'s
<a for=MediaTranscripts>transcripts</a>.
</p>

<h2 id="the-media-transcript-interface">The {{MediaTranscript}} interface</h2>

<pre class="idl">
enum MediaTranscriptType {
"subtitles",
"captions",
"descriptions",
"metadata",
};

[Exposed=Window]
interface MediaTranscript {
readonly attribute MediaTranscriptType type;
readonly attribute DOMString speaker;
readonly attribute double startTime;
readonly attribute double endTime;
readonly attribute DOMString text;
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};

dictionary MediaTranscriptInit {
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MediaTranscriptType type = "subtitles";
DOMString speaker = "";
double startTime = 0;
double endTime = 0;
DOMString text = "";
};
</pre>

<p>
A {{MediaTranscript}} object is a representation of a single piece of
transcript information.
</p>

<p>
A {{MediaTranscript}} has an associated <dfn for="MediaTranscript">type</dfn>
which is an enum of {{MediaTranscriptType}} to indicate the purpose of the
transcript. {{MediaTranscriptType}} can have one of the following values:
</p>
<ul>
<li>
<dfn enum-value for=MediaTranscriptType>subtitles</dfn>: transcription or
translation of the dialogue, suitable for when the sound is available but
not understood by the users.
</li>
<li>
<dfn enum-value for=MediaTranscriptType>captions</dfn>: transcription or
translation of the dialogue, sound effects, musical cues, and other
relevant audio information, suitable for when the soundtrack is unavailable.
</li>
<li>
<dfn enum-value for=MediaTranscriptType>descriptions</dfn>: textual
descriptions of the video component of the media, intended for audio
synthesis when the visual component is unavailable.
</li>
<li>
<dfn enum-value for=MediaTranscriptType>metadata</dfn>: information intended
for use from scripts and usually not visible to the users.
</li>
</ul>

<p>
A {{MediaTranscript}} has an associated
<dfn for="MediaTranscript">speaker</dfn> which is a DOMString of the name or
character identifier for the speaker.
</p>

<p>
A {{MediaTranscript}} has an associated
<dfn for="MediaTranscript">startTime</dfn> which is double.
</p>

<p>
A {{MediaTranscript}} has an associated
<dfn for="MediaTranscript">endTime</dfn> which is double.
</p>

<p>
A {{MediaTranscript}} has an associated <dfn for="MediaTranscript">text</dfn>
which is a DOMString of content for the transcript.
</p>

<p>
To <dfn>create a {{MediaTranscript}}</dfn> with <var>init</var>, run the
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following steps:
</p>
<ol>
<li>
Let <var>transcript</var> be a new {{MediaTranscript}} object.
</li>
<li>
Set <var>transcript</var>'s {{MediaTranscript/type}} to <var>init</var>'s
{{MediaTranscript/type}}.
</li>
<li>
Set <var>transcript</var>'s {{MediaTranscript/speaker}} to <var>init</var>'s
{{MediaTranscript/speaker}}.
</li>
<li>
If <var>init</var>'s {{MediaTranscript/startTime}} is negative, throw a
<a exception>TypeError</a> and abort these steps.
</li>
<li>
Set <var>transcript</var>'s {{MediaTranscript/startTime}} to
<var>init</var>'s {{MediaTranscript/startTime}}.
</li>
<li>
If <var>init</var>'s {{MediaTranscript/endTime}} is negative or smaller than
<var>init</var>'s {{MediaTranscript/startTime}}, throw a
<a exception>TypeError</a> and abort these steps.
</li>
<li>
Set <var>transcript</var>'s {{MediaTranscript/endTime}} to <var>init</var>'s
{{MediaTranscript/endTime}}.
</li>
<li>
Set <var>transcript</var>'s {{MediaTranscript/text}} to <var>init</var>'s
{{MediaTranscript/text}}.
</li>
<li>
Return <var>transcript</var>.
</li>
</ol>

<p>
The <dfn attribute for="MediaTranscript">type</dfn> attribute reflects
the {{MediaTranscript}}'s <a for=MediaTranscript>type</a>. On getting,
it MUST return the {{MediaTranscript}}'s <a for=MediaTranscript>type</a>.
</p>

<p>
The <dfn attribute for="MediaTranscript">speaker</dfn> attribute reflects
the {{MediaTranscript}}'s <a for=MediaTranscript>speaker</a>. On getting,
it MUST return the {{MediaTranscript}}'s <a for=MediaTranscript>speaker</a>.
</p>

<p>
The <dfn attribute for="MediaTranscript">startTime</dfn> attribute reflects
the {{MediaTranscript}}'s <a for=MediaTranscript>startTime</a> in seconds.
On getting, it MUST return the {{MediaTranscript}}'s
<a for=MediaTranscript>startTime</a>.
</p>

<p>
The <dfn attribute for="MediaTranscript">endTime</dfn> attribute reflects
the {{MediaTranscript}}'s <a for=MediaTranscript>endTime</a> in seconds.
On getting, it MUST return the {{MediaTranscript}}'s
<a for=MediaTranscript>endTime</a>.
</p>

<p>
The <dfn attribute for="MediaTranscript">text</dfn> attribute reflects
the {{MediaTranscript}}'s <a for=MediaTranscript>text</a>. On getting,
it MUST return the {{MediaTranscript}}'s <a for=MediaTranscript>text</a>.
</p>

<h2 id="the-mediapositionstate-dictionary">The {{MediaPositionState}}
dictionary</h2>

Expand Down
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