Discs? Optical Discs like DVD or Blu-ray? Roxio Toast, which is supposed to have an AVCHD archive feature, has a problem when creating spanned discs which seems to create unsupported meta data structure. I'v/Applications/MovieConverter Studio.appe run into that so I'm just taking a shot.
If you're back is against the wall
[
www.movieconverter-studio.com]
Will convert the .mts to Apple Intermediate Codec. The free version is slow but it works.