WHATWG HTML specifies `kind="descriptions"` for `<track>` so authors can provide a script for audio descriptions for associated videos:
WHATWG HTML also provides parsing rules (including for making them extended audio descriptions):
The current WCAG advisory technique guides authors to use `<track>` with `kind="descriptions"` to provide a source for the browser to provide synthesized audio description:
A caveat is that the latest update from WebVTT CG Report suggests WHATWG HTML may have jumped the gun:
> The majority of the current version of this specification is dedicated to describing how to use WebVTT files for captioning or subtitling. There is minimal information about chapters and time-aligned metadata and nothing about video descriptions at this stage.
In other words, I would love to see this supported but if WHATWG HTML is punting to WebVTT and WebVTT has not fully specified it, then perhaps WebKitcan either:
1. take the lead and implement this, helping cement behaviors; or
2. push for clarity in WHATWG HTML using its outsized position of influence.