WebAIM - Web Accessibility In Mind

E-mail List Archives

Re: Captions not in Text-Format

for

From: Steve Green
Date: Sep 2, 2022 8:39AM

The WCAG definition of captions includes images of text embedded in video. The WCAG definition of an image of text states "text that has been rendered in a non-text form (e.g., an image)", which obviously fails the level AA success criterion 1.4.5 (Images of Text) even though the definition does not specifically mention video content. If you are only aiming to meet WCAG level A, this does not matter.
See https://www.w3.org/TR/WCAG21/#dfn-captions and https://www.w3.org/TR/WCAG21/#dfn-images-of-text

The WCAG level AAA success criterion 1.2.8 is specifically designed to address the requirements of people with both visual and hearing impairments. It requires that you provide all of the information in the synchronized media (both visual and auditory) in text form, presumably because this can be used with appropriate output devices such as Braille displays.

The WebVTT file would not usually be sufficient to meet SC 1.2.8 because it is not likely to contain the information that is presented visually in the video. The file also contains all the timing information, which would result in a lot of noise for screen reader users whether they are using audio output or a Braille display.

Steve Green
Managing Director
Test Partners Ltd