Use Closed Captioning
Closed Captioning allows live streams to have text versions of the audio rendered in-line to the video. This assists with foreign-language support, accessibility for the hearing impaired, and other scenarios.
Closed Captioning styles
The following are different styles of closed captions.
CEA-608 / EIA-608: This refers to the older style of closed captioning used by traditional analog television signals. They are inserted into the analog broadcast in
line 21. These type of captions support limited languages such as English, Spanish, French, Portuguese, Italian, German, and Dutch. There is no formatting (captions are typically white all-caps text on a black background), and they are encoded in plain text.
CEA-708 / EIA-708: This refers to the newer, updated captioning style intended for use with digital television broadcasts. 708 captions support enhanced formatting (color, font, size, background) and additional languages through the use of Unicode character sets (for example, Japanese and Chinese). These captions are typically placed in the SEI NALU of h.264 video stream as picture user data.
Support for captioning
ActionScript callback methods in the incoming RTMP Stream are generally used to pass
the 608 and 708 captions for HDS. These methods are implemented by an encoder
internally and included in the RTMP stream. Check with your encoder vendor on the
configuration options to enable captions. This captioning data will be passed
through to the HDS output.