Whenever you import AVI into iMovie on Mac, you always have a frustration that you can’t import AVI directly. Both from either from digital camcorder, both other devices. If you want to import AVI to iMovie, you must learn something.
Audio Video Interleave (also Audio Video Interleaved), known by its acronym AVI, AVI files can contain both audio and video data in a file container that allows synchronous audio-with-video playback.
In the other hand, iMovie workable video formats including MOV, MP4, M4V. So AVI is not a video format which iMovie recognized. The simple thing you should do is convert AVI to iMovie, meanwhile, you need a software application which can convert AVI to iMovie. Now, I recommend a Mac AVI to iMovie Converter for Mac users.