change DVR recording to .mkv

since update to 1.7.6, now my recordings are .ts and not .mkv
how to change back to .mkv
PMS 1.7.6.4058
HDH-Extend 20170612beta1

Setup a post processing script to convert to mkv. The ts format was probably brought back to fix issues with closed captioning/subtitles that were not working with the mkv file Plex was creating.