Any media file that has both video and audio needs to be encapsulated by a so-called “container format”. As an analogy, a video file with its corresponding audio file can be zipped together using WinZip or other utilities to create a single file – since we generally do not use two separate files for an audiovisual media file’s playing. However, WinZip or the other utilities are merely encapsulating tools that do not care much about the timing between the audio and the corresponding video – they are only concerned about “zipping” or “compressing” them into a single file.
Container formats such as the AVI (Audio Video Interleave, the most widely used container format), the MPEG (Moving Pictures Expert Group. Phase I container) or the RM (Real Media) or even the MP4 extension files are used to program the audio stream to time in with the video stream in a single file format.
Matroska’s MKV file (Matroska Video) is an open source format that is an alternative to these proprietary container formats. These files are far more advanced than the common AVI format in that they support Variable Bit Rate (VBR) for audio and Variable Frame Rate (VFR) for video streams. It can also support current-day open source audio formats such as the Ogg Vorbis audio that is an excellent open source replacement for the MP3 format. Not only is this format very flexible for present day multimedia streams, it is also built of EBML – a very flexible framework offering excellent future-proofing.
The .MKV file extension can be played by a variety of players that support open source ideologies or have specific driver-files to play these files. VLC media player is the most ubiquitous player that is known to play “anything” that is fed to it – and opening MKV format with this player is no exception. You can also convert MKV to DVD form (AVI, DIVX Format)
The Core Media Player also offers playback but is based on the DirectShow codec, and there are a number of other needs to be fulfilled before it can be used to play MKV. Additionally Zoom player and Core Player Pro and Mobile are media players that can also playback MKV file format while needing the installation of the codec.
CorePlayer is also renowned to use very little mobile system resources. Lastly, Media Player Classic – an ongoing open source project to reinvent grassroots Windows Media Player also plays MKV format videos very easily and very effectively.