PMP (Win10) direct plays VC1 video and dts audio. Plex Web (Chrome, Win10) transcodes VC1 to H264, dts to AAC.
To convert subtitles, check out Subtitle Edit, http://www.nikse.dk/SubtitleEdit/. Very easy to convert between subtitle formats. It will read directly from a MKV file, then save converted subtitles in appropriate file - .srt, .ssa, etc.
To mux converted subs back into the MKV file, check out MKVToolNix, https://mkvtoolnix.download/. It also has capability to edit headers and chapters.
