First I have to say I been looking for info about getting my subtitles to work in Roku's DS Video for the last 2 to 3 years since they decided to stop updating DS Video. I have had no problems way before that with Roku and Roku's DS Video. The subtitles worked no problem whether they were hard coded or soft coded.
I have a Synology DS718+ and a DS411 as backup, yet my DS411 use to play subtitles via DLNA years ago in DS Video. I have Video Station for my NAS at 2.4.6-1594 for both NAS*(s) right now.
I can watch hard coded subtitles on Roku's DS Video but no soft coded subtitles. Of course all in english. I been hard coding english subtitles only in foreign movies such as Eleven Samurai. I get the soft coded showing to choose from but they do not work.
I use Subtitle- Edit program and that works well! great!
I know both hard coded and soft coded subtitles show up on my PC, and Western Digital HD TV LIVE, and my IPAD2. I can turn it off or on with ease.
I have a Roku 3600X version 9.1 Build 4111-24 right now with DS Video version 1.7 on my Roku stick.
I really could use help getting them to work...I have heard that Plex users are having problems to. Synology has tried to help but I do not think they have done enough to fix this situation or if it is just ROKU DS Video app.
p.s. I use MEGUI to encode...it will hard encode or soft encode subtitles. I only do English subtitles by the way.