thanks for the reply Alex.
subtitle option is disabled in VLC, and playlist file does show subtitles
-rw-r--r--. 1 nimble nimble 1044241306 Jun 18 2016 wedding.mp4
-rw-rw-r--. 1 nimble nimble 125921 Jun 18 2016 wedding.srt
$ curl "http ://192.168.0.17:32768/vod/wedding.mp4/playlist.m3u8"
#EXTM3U
#EXT-X-VERSION:3
#EXT-X-MEDIA:TYPE=SUBTITLES,GROUP-ID="sub",NAME="English",URI="subtitle.m3u8?nimblesessionid=12",LANGUAGE="eng"
#EXT-X-STREAM-INF:BANDWIDTH=4524435,CODECS="avc1.100.40,mp4a.40.2",RESOLUTION=1280x536,SUBTITLES="sub"
chunk.m3u8?nimblesessionid=12