Currently Being ModeratedJul 29, 2011 1:58 PM (in response to JCC123)
mts are High Def video shot in AVCHD. AVCHD is designed as a container for editable material. You need to ingest this material to iMovie, process it and then export it in a viewing format.
No, it's not true that only iPhone video can be transferred to iPhoto. Any format that QuickTime supports can be added - this includes most .mov and .avi files.