MKV is a free, open source container format, developed by Matroska, which can hold an unlimited number of video, audio, picture or subtitle tracks in one file. It is more and more popular and will no doubt become the dominant video container for HD videos. However pity is that the official Apple QuickTime player doesn't support .mkv files natively, which means that you can not directly play MKV on Mac. On the other hand, there are also lots of ways…