Using a Desktop Converter for MTS File Mac Compatibility
If you aren’t interested in a permanent solution, there is an alternative that won’t require you to switch to third-party players. An MTS file can even be converted to a QuickTime-compatible format (such as MP4), ensuring its playability on any Apple system.
You’ll have to install the aptly-named "Any Video Converter". An executable is available on www.any-video-converter.com. The installation process is very ordinary.
Once that’s done, Open your .mts, set the output profile, choose the destination folder and you’re all set. There is a certain downside - the videos take some time to recode. Hence, we recommend using an MTS-capable player, such as Elmedia.