Include a sign language interpreter in videos
For many deaf people, sign language is a first language and written captions are a second one, read at speed. G54 puts an interpreter into the video itself, in the corner or beside the picture, so the audio arrives in the language they think in. W3C files it as sufficient for its sign-language rule, which is Level AAA. Captions are the Level A and AA requirement and they stay required, so this sits on top of captions rather than in place of them. Burning the interpreter into the stream carries one real drawback worth knowing before you commission it. The interpreter becomes part of the picture, so nobody can enlarge them without enlarging the whole video, and on a small player the signing stops being readable.
How we find it in an audit
Where a client has commissioned interpretation, a reviewer checks it runs through the whole video rather than the introduction, and that the framing holds hands, face and upper body in shot, since sign language uses all three at once. Then the video gets played at phone size, because that is where a burned-in interpreter usually stops being legible. Deaf reviewers do this part, since a hearing reviewer can confirm an interpreter is on screen and cannot judge whether the interpretation is any good.
How affected users experience it
A deaf viewer whose first language is sign reads captions rather as a hearing person reads a language they studied at school. It works, it costs effort, and fast dialogue outruns it. An interpreter takes that translation step away, so tone, emphasis and the words a speaker leans on all survive. Deaf children and adults with lower written literacy gain the most, because for them captions can be close to no access at all.
Passes vs. fails
Passes
The same announcement carries an interpreter, framed with hands and face in shot, and still legible when the player is phone-sized.
Fails
A policy announcement ships with captions only, delivered fast and in dense legal language.
Other ways to satisfy this rule
4 guides on this site are filed under 1.2.6 Sign Language (Prerecorded). W3C lists this one as sufficient for that rule on its own. Implement it correctly, in a way your readers' software actually supports, and the rule is met.
This guide is our interpretation of W3C technique G54: Including a sign language interpreter in the video stream. W3C publishes its techniques as guidance rather than as the standard, and says so on every one of them. The success criterion is what conformance is measured against, and a technique is one documented way to meet it.