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Re: Captions not in Text-Format


From: wolfgang.berndorfer@zweiterblick.at
Date: Sep 3, 2022 4:57AM

Thank you, Steve for clarification concerning SC 1.4.5 and the hint to SC 1.2.8!

So, caption files seem to be the solution for the realization of captions. Or are there any other mechanisms to pass 1.4.5 in videos?

And what do we know about captions for SR users?

In my third question I didn't mean that the caption file should be read with the SR, just like I do not read the HTML Code. My question is, how these files are rendered and supported by UA/AT.

I just started to learn about WebVTT and tried out the first example that Google brought:
I found a way in Chrome with JAWS to navigate to the caption text. Don't ask me how I found the captions again after pressing pause or play…

There seems to be no mechanism available to jump to a caption in JAWS and NVDA. And a mechanism that puts out the current caption at my braille display, while I listen to a video, has to be found yet.

Are captions underestimated by AT?


-----Original Message-----
From: WebAIM-Forum < <EMAIL REMOVED> > On Behalf Of Steve Green
Sent: Friday, September 2, 2022 4:40 PM
To: WebAIM Discussion List < <EMAIL REMOVED> >
Subject: Re: [WebAIM] Captions not in Text-Format

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

-----Original Message-----
From: WebAIM-Forum < <EMAIL REMOVED> > On Behalf Of <EMAIL REMOVED>
Sent: 02 September 2022 14:30
To: 'WebAIM Discussion List' < <EMAIL REMOVED> >
Subject: [WebAIM] Captions not in Text-Format

Captions may be provided in a caption-file OR as pure graphic in a video.
The definition says: "synchronized visual and/OR text alternative."

So pure graphical captions pass SC 1.2.2 and 1.2.4.

But what about people who are hard of hearing AND visually impaired?

And what about SR users who want to find out the correct spelling of an unknown term or name?

"For optimum accessibility, provide a separate caption file of the description of visual information."

( <https://www.w3.org/WAI/media/av/captions/>

1. Are graphical captions an issue for SC 1.4.5 Images of text? Neither the
Understanding examples nor techs suggest that.

2. Is there any other SC that covers the problem?

3. Is a caption file (WebVTT, .) the obvious text alternative regarding to SR support?

Thanks for clarification!