Is SDH the same as closed captions?

Close in content, different in origin and delivery. SDH is a subtitle file carrying caption-style information; closed captions are a broadcast caption track.

Should SDH be verbatim?

It should be faithful and readable. Reading-speed limits apply as they do to any subtitle, so light condensing is expected.

How are sound effects written?

Usually in brackets and only where they matter to understanding — [door slams] rather than every ambient noise.

Should SDH be supplied as a separate file from the subtitle track?

Yes. They are different deliverables for different audiences, tagged separately, and a viewer choosing standard subtitles should not receive sound descriptions they did not ask for.

Definition

What Is SDH?

VideoText editorial team. Updated September 13, 2026.

Direct definition

SDH means Subtitles for the Deaf and Hard of Hearing. An SDH track includes dialogue plus sound cues and speaker identification so viewers who cannot hear the audio still get that information.

The sections below explain how SDH is used in transcription and subtitle work, what people often mix up, and which VideoText workflow applies when the next step is a file or review pass.

Key takeaways

SDH is a content profile, not a file extension.
SDH describes who the text is written for; “closed” describes whether the viewer can toggle the track.
Sound effects belong in SDH/captions; they are usually omitted from translation-only subtitles.

SDH vs closed captions

In practice the content goals overlap. “Closed captions” describes how the track is toggled. “SDH” describes who the text is written for. A closed SDH track is common on discs and streaming stores.

What SDH includes that subtitles do not

Subtitles for the deaf and hard of hearing carry the dialogue plus the audio information a hearing viewer gets for free: speaker identification, relevant sound effects, and indications of music or tone where it carries meaning.

The convention is to distinguish these additions visually, commonly with square brackets or parentheses, so the viewer can tell narration of sound from spoken words.

Why SDH exists alongside closed captions

Closed captions and SDH serve the same audience but come from different technical traditions — captions from broadcast signal encoding, SDH from the subtitle workflow used for home video and streaming.

In practice a streaming platform will ask for an SDH subtitle file where a broadcaster would ask for a caption track, and the editorial content of the two is very similar.

Frequently asked questions

Is SDH the same as closed captions?: Close in content, different in origin and delivery. SDH is a subtitle file carrying caption-style information; closed captions are a broadcast caption track.
Should SDH be verbatim?: It should be faithful and readable. Reading-speed limits apply as they do to any subtitle, so light condensing is expected.
How are sound effects written?: Usually in brackets and only where they matter to understanding — [door slams] rather than every ambient noise.
Should SDH be supplied as a separate file from the subtitle track?: Yes. They are different deliverables for different audiences, tagged separately, and a viewer choosing standard subtitles should not receive sound descriptions they did not ask for.

Related terms

Sources

W3C WAI: Captions/Subtitles