{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "$id": "https://readium.org/webpub-manifest/schema/extensions/epub/metadata.schema.json",
  "title": "EPUB Profile - Metadata",
  "type": "object",
  "properties": {
    "mediaOverlay": {
      "type": "object",
      "properties": {
        "activeClass": {
          "description": "Author-defined CSS class name to apply to the currently-playing EPUB Content Document element.",
          "type": "string"
        },
        "playbackActiveClass": {
          "description": "Author-defined CSS class name to apply to the EPUB Content Document's document element when playback is active.",
          "type": "string"
        }
      }
    }
  }
}