But there are times you cannot import video to iMovie 10 even it is in Apple friendly MP4, MOV, M4V, and even it is from Camcorder.

By the feature of importing video from a camcorder in iMovie 10, you can import most video to iMovie 10 from camcorder in MTS, MXF, XAVC. However, video importing in iMovie 10 is still restricted to Apple friendly video formats including MP4, MOV, M4V. You can select, mark as Favorite and add to your movie before the file has even copied. And the import process in iMovie 10 has now been back-grounded, meaning that you don’t need to wait for an import to complete before working with the footage. You can choose to importing from a camcorder, importing from an iOS device, importing from a point-and-shoot camera and importing existing movies. With iMovie 10, import is fast and really a joy. launched the stable version iMovie 10 which bundled with all new Macs and for separate purchase from the Mac App Store. And along with the release of macOS 10.14 Mojave, macOS 10.13 High Sierra, macOS 10.12 Sierra, OS X EL Capitan, OS X Yosemite 10.10, Mavericks 10.9, Apple Inc. Along with the release of OS X 10.9 Mavericks, Apple also updated its popular entry-level video editor, iMovie to iMovie 10 with major changes to the interface to make it easier to import video, create and share your videos.

How to open avi files in imovie