Some people said that QuickTime can change its format after it is opened, but QuickTime can't open mpg format either. I want to edit it with iMovie, but I can't import it to iMovie. See the following example: I have a video in AVI format. However, when they both appear on Mac, problems appear. IMovie and AVI are widely used for editing and saving video.
How to Import AVI Video Files to iMovie on Mac