Why an AVI video file cannot be imported to iMovie? I'm using iMovie and try to import a .avi file, 730.5MB. But iMovie keeps saying that "None of the selected files or folders can be imported. Change the selection and try again."

Small .avi files created by my camera are able to be imported, but the 730.5MB one cannot, which was downloaded from Internet. Why can't it be imported? Is it because of its size too large?
I can't tell you why some AVIs can be imported but this one can't, but if you know that the file itself isn't corrupt or anything, I can give you a remedy: Handbrake is an app that can convert almost any video format to MP4, which iMovie should definitely be able to handle. Open Handbrake, select your video file, enter the destination path you want if you don't like the default, and press Start to run the conversion. When it's done, see how iMovie reacts to the MP4. Good luck!