Offer a synchronized sign language video track
Sign language interpretation delivered as its own video stream, synchronized with the main one, which the player can overlay or show in a second window. G81 is that route, and W3C files it as sufficient for its sign-language rule at Level AAA, using a more specific technique. It is the better of the two interpretation routes for one concrete reason. Because the interpreter is a separate stream, a viewer can enlarge them without enlarging the whole video, and anyone who does not need interpretation never has to see it. Burning the interpreter into the picture costs you both of those. Captions stay the Level A and AA requirement either way, so this sits on top of captions rather than in place of them.
How we find it in an audit
Where a client offers interpretation, we check the delivery route first, since a separate stream and a burned-in one are different findings with different fixes. Then a reviewer confirms the two streams stay in sync for the whole runtime, that the interpreter window can be resized and moved, and that turning it on is discoverable in the player rather than buried in a settings menu. Deaf reviewers judge the interpretation itself, because a hearing reviewer can only confirm that somebody is signing.
How affected users experience it
A deaf viewer who signs gets the content in their own language, at the speed people actually communicate in, rather than as text going past at the speed the speaker talks. The separate stream adds the thing captions and burned-in interpreters both lack, which is control. Make the interpreter bigger on a small screen. Move them off the part of the picture that matters. Turn them off in a room where somebody else is watching. Those choices are what make an accommodation usable rather than merely present.
Passes vs. fails
Passes
An Interpreter toggle adds a resizable, movable interpreter video, frame-synced to the main track and off until it is asked for.
Fails
Interpretation exists only as a tiny fixed inset, unreadable at mobile sizes and covering the slides on a desktop.
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 when it is implemented through a more specific technique, so the condition is part of the test rather than a footnote to it.
This guide is our interpretation of W3C technique G81: Providing a synchronized video of the sign language interpreter that can be displayed in a different viewport or overlaid on the image by the player. 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.