Importing AVCHD uncrecognizable file format

How do I get iPhoto to recognize the files if I get the unrecognizable file type message when drag & dropping AVCHD files? I made sure to import .mts files individually or all enclosed on the BDMV folder and always get the unrecognizable file format error message.

Converting using Handbrake is an option, but iPhoto now accepts the AVCHD format as native, so I would not like to waste CPU time on this...

Thanks,

Ivan