Learn about captions


Captions and subtitles are types of time-synchronized text that help your viewers to understand the audio components of your video content.

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Screenshot of an English caption in a video


Synchronized TextDescription
CaptionsA caption displays the text of the original audio and includes non-speech elements like noises.
SubtitlesUsed when the viewer has the ability to hear the content but does not understand the language of the video content

A subtitle translates the text of the original audio into a different language. Non-speech elements are not captured.

For simplicity, both captions and subtitles are referred to as captions in our documentation.

JWP supports the rendering of captions in the video display. A viewer can enable captions by clicking the CC icon.

When added to your video content, captions provide several benefits to you and your viewers.

Publishers / Broadcasters / CreatorsVIEWERS
• Increasing the discoverability of your content through video SEO
• Adhering to legal requirements
• Showing text explanations of audio
• Increasing content retention
• Enabling viewers to watch video content in quiet environments


Supported caption types

Captions can either be embedded in the video (embedded captions) or loaded from a separate file (side-loaded or sidecar captions). The web player supports both types of captions.

The following table lists common caption formats that are supported.

FORMATTYPEDESCRIPTION
CEA-608 / CEA-708EmbeddedUsed in videos that originally were on broadcast television

Captions are included as part of the video content. These captions are styled according to the device's captions and subtitle settings that the viewer sets.
WebVTT (.vtt)Embedded or
Side-loaded
Common format used for online video

Captions can be embedded as part of a live stream or can be side-loaded as a separate file. WebVTT captions can include the caption, a description, and metadata information.

Your .vtt files should be saved using UTF8 encoding to prevent rendering issues.
SubRip Text (.srt)Side-loadedCommon format used for online video

SubRip Text captions only include the caption. Neither description nor metadata information can be included.
Timed Text Markup Language (.dfxp, .ttml, .xml)Side-loadedXML-based format used for online video

Formerly known as Distributed Format Exchange Profile (DFXP), this format is adopted widely by the television industry. Currently, JWP supports ttml1.


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