str sub titles

[aapeli]

I have GigaBlue QuadPlus, OpenViX 5.1.031 (2018-07-11), kernel 4.8.3 / 20180403

As cable tuner, works fine, but the problem is when I download (legally) a movie as mp4, sub titles came as Unicode-8 coded str file. File name is same, movie ends to.mp4, and subtitles to .str

mp4 plays, but I can not get sub titles. I've enabled dvb-sub titles. Usual trick to get sub titles by pressing twice the audio button on the remote, but in this case it only opens an empty window.

Googling the problem showed results, which suggested installing sub title loader, but I can not find such in plugins.

How could I see the sub titles?

[aapeli]

Problem solved, in the str file there was three letter country code before .str, I removed it, and now truelly mp4-video and str-file names differ only from last dot on, mp4 or .str