- * open captions: text that is shown to everybody on-screen (aka subtitles).
- * closed captions: text that is shown to some viewers using some other method.
+ * The generally accepted definitions seem to be:
+ * - subtitles: text for an audience who doesn't speak the film's language
+ * - captions: text for a hearing-impaired audience
+ * - open: on-screen
+ * - closed: only visible by some audience members
+ *
+ * At the moment DoM supports open subtitles and closed captions.