load subtitles file without dialog opening

[mangup]

How can i load subtitles file without open-file-dialog opening? (when user select some mp4-embeded subtitle Track - open some known file)
May be to post some event to some appropriate queue? or other way?

[InTheWings]

rename with same file name, but keep subtitle ext.

Foo.mp4
Foo.srt

[mangup]

not that.
I have fragmented mp4 file with multiple subtitle tracks. some of them are not fragmented and vlc does not play them. But it can to play them, if they are extracted to external file.
I want to mark (some how) that tracks and load external file when user select one of that tracks from menu.

[unidan]

you have to use the input slave system to join your main media with the subtitle media.

[mangup]

during playing with input slave system I've found:
1. a segfault in webvtt: https://trac.videolan.org/vlc/ticket/22448
2. [input-slave] failed to identify SAMI subtitles: https://trac.videolan.org/vlc/ticket/22451