Live Closed Captioning Software and Services

Live Closed Captioning Software and Services

Integrate Closed Captions in Adaptive Bitrate Streaming Video

As part of the Twenty-First Century Communications and Video Accessibility Act of 2010, The FCC requires any content offering closed captions when broadcast on television to also be captioned when distributed over the internet. The Wowza Streaming Engine™ software integrates closed captioning into streaming video, making online content accessible to a broader audience. It can ingest caption data from a variety of in-stream and file-based sources and convert it to the appropriate format. Additionally, the Wowza Streaming Cloud™ service offers closed captioning for live streaming video delivered via our global cloud platform.


Make Your Video Streams More Widely Accessible

There are a number of reasons to use live closed captioning software or services. Beyond increasing inclusion, captions can improve comprehension for viewers — especially those with limited proficiency in the language. Plus, with so many viewers accessing content on the go, captions ensure that the message is conveyed despite any background noise. And like most efforts to improve accessibility (such as using alt text on a website), video captioning software enhances search engine visibility and content analysis.

Benefits of Closed Captioning for Live Streaming Video:

  • Ability to reach viewers in multiple languages
  • Making content available to people with disabilities such as hearing loss
  • Compliance with the United States FCC Twenty-First Century Communication and Video Accessibility Act (CVAA) of 2010

Support for a Wide Array of Closed-Caption Formats

Just as there are countless protocols, formats, and playback devices for streaming video, there are several types of closed-caption formats. Each adaptive bitrate streaming standard, whether HLS, HDS, or RMTP, supports different formats for embedded captions in streamed video. Wowza Streaming Engine provides the widest range of supported caption formats and caption-conversion capabilities of any media server for live and video on demand (VOD) content, while Wowza Streaming Cloud currently only supports captioning for live videos.

See the chart below to learn more about Wowza’s live closed captioning software and services.

Caption Input Format Streaming Output Format
Apple HLS Adobe HDS RTMP
Engine (Live) CEA-608 CEA-608, WebVTT onTextData onTextData
DVB Teletext CEA-608, WebVTT onTextData onTextData
AMF onTextData CEA-608, WebVTT onTextData onTextData
AMF onCaption and AMF onCaptionInfo CEA-608, WebVTT onTextData onTextData
Captions Inserted Via API CEA-608, WebVTT onTextData onTextData
Engine (VOD) 3GPP / MPEG-4 CEA-608, WebVTT onTextData onTextData
TTML files CEA-608, WebVTT onTextData onTextData
WebVTT files CEA-608, WebVTT onTextData onTextData
SubRip Text (SRT) CEA-608, WebVTT onTextData onTextData
Scenarist (SCC) CEA-608, WebVTT onTextData onTextData
CEA-608 as SEI data CEA-608 n/a n/a
Cloud (live) AMF onTextData CEA-608 onTextData onTextData
CEA-608 CEA-608 n/a n/a

Closed Captions for Live Streams


Inbound Video — Engine

For inbound live content, Wowza Streaming Engine accepts the following formats:

  • CEA-608 captions embedded in live streams.  
  • Captions embedded as Action Message Format (AMF) onTextData in input streams.  
  • Captions embedded as AMF onCaption and onCaptionInfo in input streams.  
  • An API is provided to insert onTextData into a stream.

Through its Java API, Wowza Streaming Engine can also connect to back-end caption providers, allowing the server to ingest virtually any live caption format.


Outbound Video — Engine

For outbound video, Wowza Streaming Engine directly embeds CEA-608 or WebVTT captions in live streams played back via Apple HLS. For live events streamed via Adobe HDS or RTMP, Wowza Streaming Engine displays captions using onTextData events.

More About Live Closed Captioning With Streaming Engine


Inbound Video — Cloud

Wowza Streaming Cloud can ingest two closed-caption formats from a video source: CEA-608 (digital) and onTextData.


Outbound Video — Cloud

Wowza Streaming Cloud embeds CEA-608 captions in live streams played back via HLS, as well as captions using onTextData for delivery via HDS or RTMP.

More About Live Closed Captioning With Streaming Cloud


Closed Captions for VOD


Inbound Video — Engine

For on-demand content, Wowza Streaming Engine can convert and deliver captions that are embedded in the video content as well as captions that are delivered in external files alongside the video content, sometimes called sidecar files. Wowza Streaming Engine can extract 3GPP Timed Text caption data from MP4 files or from companion files that use the following formats to specify caption data:

  • Timed Text Markup Language (TTML)
  • SubRip Text (SRT)
  • WebVTT
  • Scenarist Closed Caption (SCC)

Outbound Video — Engine

This caption data can be injected into Apple HLS streams as CEA-608 or WebVTT captions or into Adobe HDS and RTMP streams as onTextData events.

More About VOD Closed Captioning With Streaming Engine


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