SDH
Subtitles for the Deaf and Hard-of-hearing
Subtitles that include speaker labels and non-speech audio cues like [music], [door slams], so deaf and hard-of-hearing viewers get the full experience.
In depth
SDH (Subtitles for the Deaf and Hard-of-hearing) extends regular subtitles by transcribing not just dialogue but also speaker identification and significant non-speech audio: music cues, sound effects, and ambient noise. SDH is typically delivered as same-language subtitles, distinct from translation subtitles which assume the viewer can hear.
When to use it
Use SDH when authoring captions for accessibility on streaming platforms, Blu-ray, or anywhere the audience may include deaf or hard-of-hearing viewers. Many regions legally require it.
Example
[music swells] - JOHN: Where are you going? - (door slams)
Frequently asked
What's the difference between SDH and closed captions?+
Closed Captions (CC) is a US/broadcast term for the entire system — toggleable, encoded captions that include speech and audio cues. SDH is closer to a content style: subtitle files that include the same accessibility content. Practically, SDH .srt and CC files contain very similar text.
How are non-speech sounds formatted?+
Convention is square brackets [music], parentheses (door slams), or italics, depending on the style guide. Netflix and Amazon publish detailed SDH style guides.
Should every SDH line label the speaker?+
Only when it's not visually obvious or there are multiple potential speakers off-screen. Over-labeling clutters the screen.