You need to have your video in a MKV
container and your subtitles in it. You can add them with MKVToolNix
. You need to mark them with a language there.
Then to select the subtitles you need inside of Visionaire:
game.GameVideoSubtitleLanguage = "eng"
To select a font for your subtitles:
game.GameVideoSubtitleFont = Fonts["font_name"]
If you can't render videos into MKV, i recommend using ffmpeg for conversion, however there are other softwares that might be more user friendly. ffmpeg is not that complicated though.
Btw VP9 codec is out, so i would recommend using that instead of VP8.