My code still exists in the desktop source[1] but essentially what you need to do is convert an srt to vtt [2] file and start a local http server that will serve the VTT file [3] and point the Chromecast to that
[1] https://github.com/popcorn-official/popcorn-desktop/blob/dev...
[2] https://github.com/popcorn-official/popcorn-desktop/blob/dev...
[3] https://github.com/popcorn-official/popcorn-desktop/blob/dev...