266724 2023-12-20 12:45:24 -0800 AX: Feature request: Support WebVTT-based synthesized audio description in video 2026-02-02 10:42:05 -0800 1 1 1 Unclassified WebKit Accessibility Safari 17 All All RESOLVED FIXED InRadar P2 Normal --- 1 aroselli eric.carlson andresg_22 eric.carlson webkit-bug-importer oldest_to_newest 2001151 0 aroselli 2023-12-20 12:45:24 -0800 WHATWG HTML specifies `kind="descriptions"` for `<track>` so authors can provide a script for audio descriptions for associated videos: https://html.spec.whatwg.org/multipage/media.html#attr-track-kind-keyword-descriptions WHATWG HTML also provides parsing rules (including for making them extended audio descriptions): https://html.spec.whatwg.org/multipage/media.html#playing-the-media-resource 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: https://www.w3.org/WAI/WCAG22/Techniques/html/H96 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. https://w3c.github.io/webvtt/#introduction 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. 2001153 1 webkit-bug-importer 2023-12-20 12:45:33 -0800 <rdar://problem/119949632> 2085938 2 eric.carlson 2025-01-08 17:29:06 -0800 WebKit added experimental support for Standard and Extended Audio Descriptions in 254266@main (332cd88dafc8) and 254502@main (c2f7594742ab). 2086108 3 aroselli 2025-01-09 07:46:43 -0800 Thanks, Eric. I am copying over the instructions you added to a related WHATWG discussion (https://github.com/whatwg/html/issues/10866#issuecomment-2578996539), partly so I can track this in one place: > WebKit has experimental support for both Standard and Extended Audio Descriptions. It uses the text to speech engine to render cues from a WebVTT track who's kind is descriptions. > When Extended AD is enabled, playback is automatically paused if it takes longer to speak a cue's text than the cue's specified duration. If playback is paused, it is automatically resumed when the utterance finishes. > When only Standard AD is enabled, playback is not automatically paused even if the text to speech engine has not finished speaking the cue text after the cue's end time. > These features are not enabled by default yet, but you can try them by selecting Settings from the "Safari" menu, selecting the Feature Flags pane, typing "description" in the Search box, and checking one or both features. Using Safari 18.2 on macOS 15.2 I did the following: 1. Safari > Settings... 2. chose "Featured Flags" 3. checked "Audio descriptions for video - Extended" 4. checked "Audio descriptions for video - Standard" 5. Visited the video at this anchor: https://adrianroselli.com/2023/12/ad-support-in-html-video.html#Synthesized 6. Played the video. 7. Heard no synthesized AD. I closed and opened Safari. I rebooted my Mac. I reloaded the page. I tried with only one of the two options checked (and vice versa). So either the feature does not work or my code is broken. Do you have a sample page posted somewhere that works so I can try it? 2086125 4 eric.carlson 2025-01-09 08:50:38 -0800 My apologies, I forgot one important step - you need to enable Audio Descriptions in system preferences: - Open System Settings - Open the Accessibility panel - Click on "Audio Descriptions" - Toggle the "Play audio descriptions when available" button 2086192 5 aroselli 2025-01-09 14:37:07 -0800 I have enabled those settings and confirm it works. Thank you! I see this feature has existed for over 2 years (a year before I filed this issues). When will this feature move out of experimental? 2087418 6 eric.carlson 2025-01-15 05:23:54 -0800 Pull request: https://github.com/WebKit/WebKit/pull/39076 2177221 7 ews-feeder 2026-02-02 10:42:03 -0800 Committed 306643@main (fb031eee9437): <https://commits.webkit.org/306643@main> Reviewed commits have been landed. Closing PR #39076 and removing active labels.