About closed captioning in Wowza Streaming Engine

Wowza Streaming Engine™ media server software can ingest caption data from a variety of in-stream and file-based sources and convert it to the appropriate format for video-on-demand (VOD) and live streams delivered over HLS, MPEG-DASH, and RTMP. Wowza Streaming Engine caption support helps United States broadcasters 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.

Note: In Wowza Streaming Engine, closed captioning for MPEG-DASH live streams is currently supported only when using CMAF-packaged MPEG-DASH outputs and the CMAF stream packetizer (cmafstreamingpacketizer).

Closed captioning for on-demand streams

Wowza Streaming Engine 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 HLS streams as CEA-608 captions or into RTMP streams as Action Message Format (AMF) onTextData events. For more information, see:
 

• Configure closed captioning for Wowza Streaming Engine video-on-demand streams
• Specify a closed captioning language for Wowza Streaming Engine video-on-demand streams
• Use external caption files with Wowza Streaming Engine video-on-demand streams
• Closed captioning property reference for Wowza Streaming Engine video-on-demand streams

Closed captioning for live streams

Wowza Streaming Engine can ingest in-stream closed caption information from AMF onTextData events, AMF onCaptionInfo events, or CEA-608/708 data. The Wowza Streaming Engine Java API enables AMF onTextData events to be injected into RTMP streams. The ingested caption data can be delivered as CEA-608/708 or WebVTT captions in HLS streams (MPEG-TS), CMAF-packetized HLS streams (CMAF fMP4), and CMAF-packetized MPEG-DASH streams (CMAF fMP4). For more information, see:
 

• Configure closed captioning for Wowza Streaming Engine live streams
• Ingest MPEG-TS DVB Teletext data for Wowza Streaming Engine live stream closed captions

Closed captioning for Apple iOS devices

The Apple iOS subtitling system uses WebVTT, which provides more flexibility in rendering multiple languages and languages that aren't supported in iOS CEA-608 closed captioning. Wowza Streaming Engine can convert closed caption data in VOD and live streams to WebVTT subtitles for playback on Apple iOS (version 6+) devices. For more information, see:
 

• Configure WebVTT captions for Wowza Streaming Engine iOS streams