How to enable subtitles on Reliance Jio set-top box while watching content on USB drive?

When you connect a USB to the Jio STB and start playing some video on that, the subtitles in the video won't be displayed (unless they are hard coded). Moreover there isn't any option of enabling subtitles in the STB.
There is a simple solution to that.
What you need to do is download a separate subtitle file for the respective video (or extract the subtitle file from the video). Give the same name to both the video and the subtitle file. For example: video name might be 'movie.mp4'. So subtitle name should be 'movie.srt'. Keep both the video and the subtitle file in the same folder on the USB.
Now this time when you will play the video on the Jio STB, you will get the option of enabling the subtitles.