parameter -1 with libvlc_video_set_spu doesn't work
Looking at libvlc_video_set_spu (which is what VLCKit uses in VLCMediaPlayer.m) it never accounts for the scenario where -1 is used as a parameter to disable subtitles altogether, which is how VLCKit header documentation details its usage:
/**
- Return the current video subtitle index
- \return current video subtitle index, -1 if none
- Pass -1 to disable. */ @property (readwrite) int currentVideoSubTitleIndex;
Therefore, passing -1 has no effect and the subtitles remain visible.