Live Closed Captioning Software and ServicesJanuary 29, 2020
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|
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.
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.
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)
- 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.