I own a video camera (Panasonic HC-vc720) that saves its files as mts. The format mts is not recognized by mythtv. I converted these files using handbrake software to mkv files for watching on mythtv. ffmpeg is a command line program that will also convert to mkv files. The mkv format is an open/non-propriety format.
Handbrake was installed from the terminal (Ubuntu 14.04) with the command:
sudo apt-get install handbrake