Primetime supports repackaging of WebVTT files for HLS. WebVTT files are used to mark up external text track resources for your video files. You can create separate Web VTT streams (m3u8) from an input WebVTT file. The fragment duration for WebVTT segments is derived from the FragmentDuration setting under the MP4 element of the containing stream configuration.
The following is a sample variant playlist, assuming that ' english_en_full.vtt' file is available at 'vtt/origin' relative to the base location indicated in the MP4 element:
#EXTM3U #EXT-X-MEDIA:TYPE=SUBTITLES,GROUP-ID="subs", NAME="English",DEFAULT=YES, URI="vtt/orig/english_en_full.vtt.m3u8",LANGUAGE="en" #EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=150000,SUBTITLES="subs" /vtt/video/movie.mp4.m3u8
The m3u8 for the VTT stream is shown below:
#EXTM3U #EXT-X-VERSION:3 #EXT-X-TARGETDURATION:4 #EXT-X-PLAYLIST-TYPE:VOD #EXT-X-MEDIA-TIME:12.0 #EXTINF:4,english_en.12000.vtt #EXTINF:4,english_en.16000.vtt #EXTINF:4,english_en.20000.vtt #EXTINF:4,english_en.24000.vtt #EXTINF:4,english_en.28000.vtt #EXTINF:4,english_en.240000.vtt #EXT-X-ENDLIST
WebVTT does not support the following: