Any number of applications can do this as long as you have the codec (which, since you can play, see and edit with the clips, you do): QuickTime Player, MPEG Streamclip, Compressor, even Final Cut Pro itself. Watch out for frame-rate differences, though, and since all HD is 16:9, you have to think about whether you want to try to convert the footage to anamorphic or make it letterboxed, how it fits in with your other footage, etc.
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