The problem is that the latest version of Perian 1.2.3 of Perian is not compatible with Mac OS X Mavericks (10.9), Mountain Lion (10.8) and Lion (10.7). Others recommend to install Perian, a free, open source QuickTime components which supports many different AVI media types including AVI, Divx, Xvid, etc. However, it only supports to deal with Motion JPEG only AVI files formats. To get AVI files played on QuickTime Player 10, some people suggest to download and install QuickTime 7 on your Mac, which can work with some older media formats. Solution to play AVI files on QuickTime Player 10 After upgrading to the new Mac OS X operating system, a lot of people have problem to play AVI files on QuickTime player 10, others complain that it takes long hours to convert AVI into MOV files for playing with QuickTime 10.
If you are using OS X Mavericks and later, you can also use QuickTime player to convert certain old formats that it doesn't play back directly. The QuickTime player version 10 can create, play, edit and share many media formats, including many that are no longer in common use.
