*.m2ts is supported but it may be a bad encode,dvr/dvb recording … etc
Use MKVToolnix to Remux the file (takes a couple of minutes with no quality loss)
http://www.videohelp.com/tools/MKVtoolnix
I always use this program as the 1st way to fix a file.
The new file will be a *.mkv … give it a try, as ive had pretty good success with it