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Re: Unsynchronised audio and video content


From: Steve Green
Date: May 27, 2020 6:16AM

My interpretation of WCAG's definition of "synchronised media" is that the audio and video do need to be synchronised, such as when you have a talking head i.e. the relative timing of the audio and video is important. I don't believe that merely having audio and video present at the same time is sufficient to constitute "synchronised media" if their relative timing does not matter. It would simply be "multimedia". The word "synchronised" has a very specific meaning and I don't think we can simply ignore it.

In the videos I am currently dealing with, the audio track contains all the important information. The video content is entirely decorative fluff except for a medical disclaimer that is displayed for a few seconds.


-----Original Message-----
From: WebAIM-Forum < <EMAIL REMOVED> > On Behalf Of Patrick H. Lauke
Sent: 27 May 2020 13:01
Subject: Re: [WebAIM] Unsynchronised audio and video content

On 27/05/2020 11:13, Steve Green wrote:

> I am encountering a lot of videos that contain both audio and video, but they are not synchronised.

A file that has both audio and video together is "synchronised media", where the audio and the video are synchronised. Or am I missing what you mean? (I don't believe WCAG makes any more subtle distinction about whether the audio component and video component of an a/v file need to make sense even if they weren't in time or not here...the mere fact that playing the video you get both the audio and the video happening at the same time is sufficient to class that as "synchronised media").

But, assuming that what you meant is that you have pages that have both audio-only files and video-only files. In that case, the reason why WCAG doesn't allow captions for the audio-only files is that the assumption here is there's no "place" for those captions to show ... i.e. if it's an audio-only file, it would have a play/pause button, maybe a scrub bar, but no actual large "player" area where captions would then show.
If you do somehow provide some captions (e.g. using some extra container with automatically injected captions), then those would probably count as a "transcript" of sorts and pass the requirement for audio-only.

Patrick H. Lauke

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