Aperture can manage videos.
There are several free video converters in the app store, some work better than others. Free AVCHD to Mov, AnyMP4 AVCHD Converter, and Any AVCHD Converter come to mind. You may or may not be able to play the video with VLC and then convert to Quicktime/Aperture compatible.
I do a lot of video conversion and purchased "bigasoft prores converter" which does a nice job with just about anything. The free converter version will do one file and, if thats all you are going to do, you may want to give it a shot.