I have been importing AVCHD directly of the SD card plugged into a Windows reader. Using both Panasonic and Canon cameras of various flavors. Previously I just grabbed the first clip that looked usable and just ignored all the cruft. Today I decided I really wanted to know what I am looking at.
I import by pointing the media browser at a copy of the file system folders from the SD that was plugged into the camera. So in this case its a Canon Vixia(?) camera and when I point at the file system and import I get a folder named STREAM and each clip I shot has 4 files that seem to contain identical video and audio. Normally I just grab one and work with it, but I would like to understand why there are 4 copies.
Is the audio different? Video is almost certainly identical(?) Is there a cleaner way to do this using the SD that ends with single clip in the project browser? Some weird proprietary utility?
Are you using the Media Browser or File > Import? For AVCHD, the Media Browser is the preferred method. If drilling down into the AVCHD directory manually, you'll want to locate the .MTS Files. What appear to duplicates are probably thumbnails and/or proxies used during in-camera oprations (viewing, editing, trimming, logging).
Even though you could use File > Import to drill down to the MTS files, I would stick with the Media Browser. This is, of course, after copying the entire SD card to where source footage for the project os being kept, usually in a folder that uniquely identifies the card named "Card 01", "Card 02", etc.
With tapeless formats I let how the data is organized on the card dictate how I import files. With a Panasonic AVCHD or Red camera where the files are in a direcory structure, Media Browser. With a Canon DXLR where the files are QuickTime files in in folder, File > Import.