Closed captioning provides text for the audio component of a live stream. This extends the reach of your content by including viewers who are deaf or hard-of-hearing as well as viewers who are not proficient in the spoken language.
Brightcove Live currently supports 608 captions in-band (inside h.264 headers). If captions are inside the h.264 input signal (correctly signaled in the user_data packet) those are passed through to the h.264 outputs.
If you are using a broadcast Elemental live encoder you can get captions from SDI (EIA-608/CEA-608) or other sources (SCTE-20, SCC, Teletext, DVB-Sub, Ancillary, ARIB, TTML, SCTE-27, STL, SRT, SMI) and put them into the h.264 stream that you send to us. Other broadcast grade encoders probably can do the same, but we have not formally tested them.
WebVTT captions are not supported for Live streams.
The Brightcove Player has support for in-band captions.