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SDH subtitles: what "English SDH" means, how SDH differs from closed captions, and when a delivery needs it

By the Fonti Studio post-production team · 6 January 2026

In short: SDH (subtitles for the deaf and hard of hearing) is a subtitle track in the film's own language that also carries speaker identification and sound description, delivered as a normal subtitle file. Closed captions do the same job in the US broadcast tradition; platforms treat the two as largely interchangeable, and a delivery schedule usually means one of them by "CC".

Open the subtitle menu on any streaming platform and the same pair of options appears: "English" and "English SDH." Most viewers pick one without knowing what the letters stand for, and a surprising number of people shipping film deliveries are not much more certain. SDH turns up in delivery schedules, in platform specs, and now in European accessibility law, so it is worth knowing exactly what the track is, what belongs in it, and when your title cannot ship without one.

SDH stands for subtitles for the deaf and hard of hearing. It is a subtitle track that carries everything the standard track carries, plus the audio information a viewer without access to the sound would otherwise lose: who is speaking when that is not visible, and what is happening in the soundtrack when it matters to the story.

What is actually in an SDH track

Put a standard subtitle track and an SDH track side by side and three additions account for nearly all of the difference.

• Speaker identification: When the speaker is off screen, or several people share a frame, an SDH track names the voice: [MARIA] before the line, or a label on its own line. Netflix's English Timed Text Style Guide sets the convention most of the industry follows: identifiers in square brackets, used only when the speaker cannot be identified visually, and never italicized even when the dialogue is.
• Sound description: Plot-relevant sound events are described in brackets, in the present tense: [door slams], [phone buzzes], [gunfire in the distance]. The discipline is the same as for forced narratives: only what the story needs. A track that captions every ambient rustle is as much a defect as one that misses the gunshot the scene turns on.
• Music information: Score and songs are identified where they carry meaning: [tense music building], or a song title and artist when licensing and relevance justify it, with lyrics captioned when they are meant to be followed.

One more property matters for anyone commissioning translation work downstream: SDH dialogue stays close to verbatim. A standard subtitle track condenses for reading speed; an SDH track is expected to track what is actually said, because for its audience the text is not a supplement to the dialogue, it is the dialogue.

SDH vs closed captions: same goal, different plumbing

"Closed captions" and "SDH" are often used interchangeably, and on a delivery schedule they are not the same thing.

Closed captions (CC) is, strictly, a broadcast technology tradition. In North America, captions ride in a dedicated data stream (CEA-608, and later CEA-708, carried with the broadcast signal) that the viewer's device decodes and renders. The device controls the look; positioning conventions and the boxed text style come from that world, and the regulatory framework around US television captioning is written in its terms.

SDH is a content style, not a transport: a subtitle file, in whatever format the platform ingests (TTML/IMSC for the major streamers, SRT lower down the chain), authored to include the speaker and sound information above. It renders like any other subtitle track.

The practical translation: if your buyer says "CC" and means US broadcast, expect to deliver a caption stream in an SCC-shaped world. If your buyer is a streaming platform or an international distributor, "SDH" means a subtitle file authored to the SDH style. The content requirements overlap almost completely; the file you deliver does not. (Where SDH and forced narrative subtitles fit relative to each other is its own topic: FN is the tiny track every viewer sees, SDH is the complete track for viewers without the audio, and platforms require the FN events to appear inside the SDH track too.)

When a delivery needs SDH

Three forces put SDH on a delivery schedule, and two of them have hardened recently.

• Platform policy: The major streamers expect SDH (or captions) for on-service content as standard, and their delivery specifications treat the SDH file as a first-class deliverable with its own style rules, not an optional extra.
• US regulation: The CVAA and the FCC's captioning rules made captions mandatory for most television content and for online distribution of content that aired on US television, which is why "CC" is simply assumed in any US-facing deal.
• European regulation, the new one: The European Accessibility Act (Directive (EU) 2019/882) has applied since 28 June 2025, and audiovisual media services are in scope. Access services, subtitles for the deaf and hard of hearing among them, moved from best practice toward compliance obligation across EU member states. For a distributor licensing into Europe, "do we have an SDH track?" is no longer only a platform question; it is increasingly a regulatory one, and buyers' delivery schedules reflect it.

The direction of travel is one-way. A title with no SDH track has a shrinking set of doors it can pass through, and retrofitting accessibility after a rejection costs a release window, the same arithmetic as any other delivery spec failure.

What SDH costs, and what it should cost

Here is the part that surprises distributors: if a vendor is authoring your subtitles properly, the SDH version is not a separate job. The dialogue track, the timing, the glossary, the reading-speed discipline all already exist. The SDH additions, speaker IDs where needed, sound description, music identification, are an authoring pass over material the vendor already owns.

That is why Fonti Studio includes SDH on request at no extra charge on every subtitle order: the same €100 to €400 per language, priced by runtime, whether you take the standard track, the SDH track, or both. On our reference delivery, The Last Kumite (2024), the French and Dutch tracks shipped with zero errors against the Netflix Branded Delivery subtitle spec; an SDH variant rides on exactly that foundation. A vendor quoting SDH as a second full-price deliverable is billing you twice for the same timing and translation work.

Fonti Studio is a subtitle and dubbing studio run by post-production engineers, for film distributors and sales agents. €400 per language for feature subtitles, SDH included on request at no extra charge. Flat. EUR. Reviewed and signed off before delivery.