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Re: [w3c/html] Why is there no alt attribute associated with the poster attribute on a video element (or, what's the accessible name calculation on a video element)? (#1431)

From: John Foliot <john.foliot@deque.com>
Date: Thu, 2 Aug 2018 15:24:16 -0500
Message-ID: <CAKdCpxwvCMw+2OYihNw5X98Vt79_WAoBG4d2rraeqnA9-+4i-Q@mail.gmail.com>
To: "w3c/html" <reply+0012be7335b5fa9bd8dc156c0771bcc293cfcd6d20e24b9b92cf00000001177b0f1a92a16>
Cc: "w3c/html" <html@noreply.github.com>, Mention <mention@noreply.github.com>, W3C WAI Accessible Platform Architectures <public-apa@w3.org>
Hi Owen,

I think there are a few different ways forward here: we can go back to Web
Platform WG and ask for new elements or attributes to fill the gap, or we
can look to provide the same functionality via a (potentially) new aria-*
attribute. Using an aria solution would certainly address the needs of
non-sighted users, but it would take some additional "wiring up" (perhaps a
browser extension or similar) to make the textual alternatives available to
other users who may not be using a screen reader or other Accessibility API
aware tool. While my personal preference would be to get 'native'
functionality/support directly in the browser, if browser vendors aren't
keen to pursue this at this time, we can certainly explore the aria route

As a current member of the APA WG, and a past member of the Media
Accessibility Task Force that was stood up around the original HTML5
effort, there are a few additional media-related gaps that we'd like to
also follow up on (for example, there is no direct mechanism today to link
a transcript to a media asset programmatically - another existing gap on
our radar). While I cannot speak definitively here, I suspect that this
will be discussed at more length at TPAC, which is less than 3 months away
(Oct 22 - 26). The APA agenda for TPAC is still under development, but I
will endeavor to keep you (and this list) abreast of details as they evolve.


On Thu, Aug 2, 2018 at 1:27 PM, Owen Edwards <notifications@github.com>

> Okay, this is a complicated train of thought, so please let me know if it
> isn't clear:
> W3C's recommendation for making an audio file accessible in a web page is
> to use a <video> element instead of an <audio> element, and to use a
> poster, so that there is a space in the rendered page for WebVTT text track
> subtitles of the audio to be displayed for users who are deaf or
> hard-of-hearing (see #1430 <https://github.com/w3c/html/issues/1430>).
> At that point, the poster specifically *can't* be a "poster frame" from
> the video, because there isn't any video (only audio), so it must be an
> image which explicitly not described by the WebVTT track. In theory, the
> poster could be an empty image (to just allocate a blank piece of real
> estate on the page), but I really can't imagine visual designers going for
> that. (*As an aside, a nice feature for audio-only playback would be if
> the area for rendering text tracks "rolled up" or "dropped down" from the
> player controls when playback with captions starts, but that's explicitly
> not what the "poster" is for*). *Maybe* the poster could be considered
> purely decorative, and therefore not needing a text alternative, but that
> can't be guaranteed. It might be "cover art", which is entirely separate
> from the content of the song and needs its own text alternative.
> So how do site designers/developers add alternative text to *that*
> poster? Either the proposal that using a <video> element with a poster
> and text track to make a piece of audio accessible is flawed, or there are
> real situations where the poster needs an alt attribute.
> —
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*John Foliot* | Principal Accessibility Strategist

Deque Systems - Accessibility for Good

Received on Thursday, 2 August 2018 20:25:14 UTC

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