Wowza Media Server^® 3.5.0 and later can ingest caption data from a variety of instream and file-based sources and convert it to the appropriate caption format for video on demand and live streaming using the Apple HTTP Live Streaming (Apple HLS), Adobe HTTP Dynamic Streaming (Adobe HDS), and RTMP protocols. This feature helps U.S. broadcasters to comply with the Twenty-First Century Communications and Video Accessibility Act of 2010 by providing captioning for television programs that are distributed over the Internet.

Closed captioning for video on demand streams

Wowza Media Server can extract 3GPP Timed Text caption data from MP4 files or from companion files that use Timed Text Markup Language (TTML), SubRip Text (SRT), Web Video Text Tracks (WebVTT), or Scenarist Closed Caption (SCC) formats to specify caption data. This caption data can be injected into Apple HLS streams as CEA-608 captions or into Adobe HDS and RTMP streams as Action Message Format (AMF) onTextData events. For more information, see the following articles:

• How to configure closed captioning for video on demand streaming
  
• How to configure closed captioning language selection for video on demand streaming
  
• How to serve sidecar caption files for video on demand streaming
  
• Closed captioning configuration reference for video on demand streaming

Closed captioning for live streams

Wowza Media Server can ingest instream closed caption information from Action Message Format (AMF) onTextData events or CEA-608 data. An Application Programming Interface (API) in Wowza Media Server enables AMF onTextData events to be injected into Adobe HDS and RTMP streams. The ingested caption data can also be delivered in in Apple HLS steams as CEA-608 captions. For more information, see the following articles:

• How to configure closed captioning for live streaming

Closed captioning for Apple iOS 6 devices

The Apple iOS 6 subtitling system uses Web Video Text Tracks (WebVTT), which provides more flexibility in rendering multiple languages and languages that aren't supported in iOS CEA-608 closed captioning. Wowza Media Server 3.6 can convert closed caption data in video on demand (VOD) and live streams to WebVTT subtitles for playback on Apple iOS 6 devices. For more information, see the following article:

• How to use WebVTT subtitles on iOS for closed captioning

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