Our HLS video stream has webVTT subtitles as a separate stream in manifest . On all other players (videoJS, exoplayer, all Akamai hls tester) the subtitle stream displays. We cannot get the subtitle to show on our roku player or the roku stream tester http://devtools.web.roku.com/stream_tester/html/
Test stream: https://content.uplynk.com/697d92f97beb4d77942c94674d6efef1.m3u8
Our test player successfully showing subtitles: https://content.uplynk.com/player5/1ADErQKvRggNvu230hEnUcsa.html
After many hours of troubleshooting we discovered that the issue is in the way the subtitles are written in the HLS manifest by the transcoder
if DEFAULT is changed to YES then the subtitles play in Roku
Roku is the ONLY player that cannot show (Amazon Fire and all the other video players can display fine).
Does anyone have any suggestions other than going back to the transcoder?