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Sign-language video

Sign-language video brings with it a number of accessibility problems not found in spoken-language video.

Captioning principles

Captions are a transcription of speech and other auditory phenomena. Transcription means rendering speech in the writing system of that language. By definition, sign language can’t be captioned; gestural languages don’t have a writing system. (Notations have been developed for general human movement and for specific sign languages, but we are unaware of any sign language with a native companion writing system.)

Given the definition above, some sign-language video will be uncaptionable: In order to caption, we need a soundtrack.

Categories and options

Sign language with no audio
A sign-language video with no voice or soundtrack whatsoever cannot be captioned, with the sole exception of adding a single caption along the lines of [No sound]. It can, however, be subtitled into some other written language.
Sign language with no speech
A video with sign language, without speech, but with sound effects, music, or incidental audio can be captioned. Only the non-speech information (NSI) soundtrack is captioned, not the sign. The subvocalizations uttered by some signers are captionable. The sounds made by contact of signing hands against each other and against clothing or body parts are probably not worth captioning, but exceptions may occur. (In some cases, [No sound] will not be a correct caption because sound is very much present; [No voice] might be more correct.)
Video with some sign language and, at other moments, speech
Segments of sign language unaccompanied by speech cannot be captioned. NSI and speech can be captioned throughout. In some productions, for example, one actor speaks and another signs. If there is no voice for the signing actor, only the speaking actor gets captioned. In this example, sign language may or may not be subtitled.
Sign language with interpreter
A sign-language video with dubbing by a voice interpreter can be captioned. This category includes programs where the focus of attention is a signing person and programs with an interpreter displayed in a picture-in-picture, cameo, or split screen. It includes both extemporaneous interpretation done on the spot and scripted interpretation read by an actor in synchrony with the signs. Caption only the interpreter’s words even if they are known to be at variance with the meaning of the sign. The interpreter may not utter words in the language associated with the sign language (e.g., British Sign Language may be interpreted into French). If the captioner does not speak or understand the interpreter’s language, a caption similar to [Interpreter speaking French] may be used; do not fail to note the presence of speech.