Though MTS and M2TS files are accepted by many software, they fail to play on some devices like iPad, iPhone, PSP, PS3/4, Zune, etc. Moreover, if you want to edit the recorded M2TS/MTS files on some software like

For converting MTS and M2TS files into the compatible formats, Free MTS Video converter will be the ideal solution. This free M2TS/MTS converter is the totally free video conversion software without watermark.

Step 1. Add MTS/M2TS files
Free download this software to your computer, install and launch this software on your computer.

Step 2. Add MTS/M2TS files
Click Add File(s) button to import one or more MTS or M2TS files into this program. If you have stored the MTS files on your camcorder, then just use the USB cable to connect the camcorder to this computer.

Step 3. Convert MTS/M2TS
Select the output file from the drop-down list of Output format. Here you can select MP4, MOV, or other formats.

Click Convert to start converting MTS/M2TS files immediately.

Optionally, you can click Edit to add the opening and ending themes for your recording.

More reading: https://www.free-videoconverter.net/tips/mts-vs-m2ts/