Perian

Having the right codecs is essential for playing videos in certain formats. If you don't want to search for codecs on the Internet each time you encounter a new video format, then you should install Perian on your Mac. Its purpose is to extend QuickTime's compatibility so it would support many other media formats. It is a single package, which contains various libraries, for numerous video and audio formats.

Installing Perian on a Mac is a trivial task. All you have to do is extract a file from a DMG archive and run it. This will add a new menu in the System Preferences and interacting with its options is not mandatory. The new menu includes only a few options, for removing Perian, checking for updates, selecting an audio output device and for setting a different soft sound volume. It is also possible to set Perian to load external subtitles whenever they are available.

There is nothing else you have to do besides installing Perian. When the operation is complete, you will be able to play media files in various formats, including MPEG, AVI and MKV, with subtitles in mostly any format. The best part is that you can play them without installing any additional codecs.