MPG is one of a number of file extensions for MPEG-1 computer files. QuickTime support the playback of MPG files. However, if you want to import the MPG files to iMovie for edting, you’ll find that the MPG files just grey out! Or, some Mac users found that then they play some particular MPG video in QT, there’s only audio or even worse, QT crashed! In cases like these, you can convert your MPG videos to QuickTime MOV on Mac.