First my Roku setup... Multiple Roku Ultra (4660x) devices, all running the most current software connected via a wired connection to my network. Synology NAS DLNA server connected via wired connection. Both Roku Ultra and Synology NAS are on the same network hosted by an ASUS router.
I have 4 Roku Ultra devices (4660x series) that I typically stream MKV files with embedded subtitles from my Synology NAS. The Synology NAS has a DLNA server that works very well with the Roku Ultra devices where discovery of the files and the ability to stream them by the Roku devices is practically flawless. However, I have noticed some curious subtitle behavior when I stream these MKV files...
My Roku devices all have the settings of "Captions always on" with the preferred caption language being English. When streaming via the Synology NAS, the MKV file's embedded English subtitles (the subtitles are properly tagged "English" inside the MKV file) will never automatically appear - regardless of how they are tagged or defaulted inside the MKV file. In order to have the subtitles appear I must use the Roku "*" button and go to the "Accesibility and Language" --> "Captioning Track" where it always has "Other" as the selected subtitle track. When I open the "Captioning Track" setting it will show the embedded MKV "English" subtitle track below "Other" and once selected - the English subtitles are displayed during playback. Of note - there is no "Other" subtitle track in the actual MKV file - there is only the "English" tagged subtitle track in the MKV file.
Here's the curious part...Playing that exact same MKV file with the embedded English subtitle via the Roku's USB port yields a different subtitle experience. When played through the Roku's USB port - the Roku media players automatically recognize the embedded "English" subtitles where it automatically selects and displays when the file is played (IAW the Roku devices internal settings).
For some reason the Roku player cannot automatically select and display the embedded MKV English subtitle when streaming from the NAS but when that same MKV file is played through the Roku's USB port - it can IAW the Roku's settings.
Admittedly it's only a minor annoyance when streaming to go through the "*" menu to manually select the "English" track but I find it odd that the Roku cannot automatically select this track for display when streaming as it does from the USB port. The Roku obviously recognizes the "English" subtitle track when streaming (otherwise it wouldn't list it in the "Captioning Track" menu) but for some reason won't select it IAW the Roku's English captioning settings.
Anyone from Roku have an explanation?? Is this a DLNA thing, Roku peculiarity or some hidden Roku setting that I'm missing??
