Closed captions
Closed captions are on-screen text that shows a video's dialogue plus important sounds, such as music, laughter or a door slamming, and can be turned on or off by the viewer. Closed captions are written mainly for people who are deaf or hard of hearing. They are delivered as a separate text track, such as WebVTT, or embedded in the video stream as CEA-608 or CEA-708 data.
Why it matters
Captions make video usable for deaf and hard of hearing viewers and for anyone watching with sound off. In many places they are a legal or procurement requirement. They also make spoken content searchable, which helps discovery for learning and media libraries. The same FastPix API that captions a video can also return its transcript and chapters, so captions and search come from one integration.
How it works
- Speech and important sounds are transcribed, by people, speech recognition or both.
- The text is split into short cues, each with a start and end time.
- Cues are saved in a caption format such as WebVTT, or embedded in the stream as CEA-608/708.
- The player shows the right cue at the right time, and viewers can turn captions on or off.
What is the difference between closed captions and subtitles?
Closed captions include speech plus important sounds, like music or a door slamming, for viewers who cannot hear the audio. Subtitles usually show only spoken dialogue, often translated, for viewers who can hear but do not understand the language. Both can be turned on or off, unlike open captions burned into the video.
Are closed captions required by law?
Often, yes. In the US, rules such as the ADA, Section 508 and FCC rules require captions in many settings, and WCAG lists captions for prerecorded video as a basic requirement. Requirements vary by country, sector and audience, so check with legal advisors for your situation.
How accurate are automatic captions?
Automatic captions are usually accurate on clear audio with one speaker, and weaker with accents, crosstalk, jargon or background noise. For public, legal or training content, have a person review the captions, especially names and technical terms. Many teams use automatic captions as a fast first draft and then edit.
Where it's used
Online learning platforms, corporate training teams, news publishers and OTT services caption videos to meet accessibility rules, support sound-off viewing and make content searchable.
Where it usually goes wrong, and how FastPix handles it
Captioning by hand is slow and costly, so many teams skip it for live streams or large libraries and then fall short of accessibility requirements.
Captions come from FastPix's in-video AI, with multiple language tracks for on-demand video. During a live stream, real-time speech-to-text captions run on the same platform. Captioning stops being a backlog, so live events and older libraries no longer go out uncaptioned.
By the numbers
- WCAG lists Captions (Prerecorded) as success criterion 1.2.2 at Level A, the most basic conformance level. (Understanding SC 1.2.2 Captions (Prerecorded), W3C)
