Provide more accurate media kinds

index.bs

@@ -1082,8 +1082,10 @@ dictionary MediaMetadataInit {
 
 enum MediaKind {
   "advertisement",
-  "generic",
-  "pregeneric",
+  "closing-credits",
+  "cold-open-scene",
+  "opening-credits",
+  "post-credits-scene",
   "summary",
   ""
 };
@@ -1108,8 +1110,41 @@ enum MediaKind {
 
 <p>
   A {{MediaMetadata}} has an associated <dfn for="MediaMetadata">kind</dfn>,
-  which is a {{MediaKind}}.
+  which is a {{MediaKind}}, which can have one of the following value:
+  <ul>
+    <li>
+      <dfn enum-value for=MediaKind>advertisement</dfn>: the media content represents advertisments.
+    </li>
+    <li>
+      <dfn enum-value for=MediaKind>closing-credits</dfn>: the media content represents closing credits,
+      typically happening at the end of a video.
+    </li>
+    <li>
+      <dfn enum-value for=MediaKind>cold-open-scene</dfn>: the media content represents a cold open scene,
+      typically happening at the very beginning of a video, before opening credits.
+    </li>
+    <li>
+      <dfn enum-value for=MediaKind>opening-credits</dfn>: the media content represents opening credits
+      typically happening at the beginning of a video.
+    </li>
+    <li>
+      <dfn enum-value for=MediaKind>post-credits-scene</dfn>: the media content represents a post credits scene,
+      typically happening after the closing credits.
+    </li>
+    <li>
+      <dfn enum-value for=MediaKind>summary</dfn>: the media content represents a summary,
+      typically happening at the beginning of a TV serie episiode and summarizing past episodes.
+    </li>
+    <li>
+      the empty string: the default value of media content, it represents any other value of a part of media content.
+    </li>
+  </ul>
 </p>
+  "advertisement",
+  "credits",
+  "precredits",
+  "summary",
+  ""
 
 <p>
   A {{MediaMetadata}} has an associated sequence of <dfn