This technique relates to:
- Success Criterion 1.2.1: Audio-only and Video-only (Prerecorded) (Advisory)
- Success Criterion 1.2.3: Audio Description or Media Alternative (Prerecorded) (Advisory)
- Success Criterion 1.2.5: Audio Description (Prerecorded) (Advisory)
- Success Criterion 1.2.7: Extended Audio Description (Prerecorded) (Advisory)
The objective of this technique is to use the HTML5
track element to specify a descriptions timed text track for a
video element. Audio description timed text tracks contain textual descriptions of the
video component of the media resource, intended for audio synthesis when the visual
component is obscured, unavailable, or not usable. The user agent makes the cues available
to the user in a non-visual fashion, for instance, by synthesizing them into speech.
src attribute of the
track element is an URL providing the text track data.
The audio description cues must fit into the gaps available in the audio component of the media resource. If there is not enough time to synthesize the description text in the track cue's time interval, user agents may truncate the speech. This limits the amount of supplementary information that can be added.
User agents may also support extended audio descriptions by halting the video until the description has been completely synthesized, then restarting the video.
Example 1: Audio description in one language
video element for a video in the English language. The audio descriptions are provided
in the WebVTT format.
<video poster="myvideo.png" controls> <source src="myvideo.mp4" srclang="en" type="video/mp4"> <track src="myvideo_en.vtt" kind="descriptions" srclang="en" label="English"> </video>
Example 2: Audio description in multiple languages
video element for a video with both an English and French language source element, and
with an English and a French audio description track using the WebVTT (vtt) file format.
<video poster="myvideo.png" controls> <source src="myvideo.mp4" srclang="en" type="video/mp4"> <source src="myvideo.webm" srclang="fr" type="video/webm"> <track src="myvideo_en.vtt" kind="descriptions" srclang="en" label="English"> <track src="myvideo_fr.vtt" kind="descriptions" srclang="fr" label="French"> </video>
Resources are for information purposes only, no endorsement implied.
video element used to play a video:
- Check that the video contains a
kinddescriptions in the language of the video.
- Check #1 is true.