Matroska's MKV "universal" Container is described by its developers as "the extensible open standard Audio/Video Container." This translates to a multimedia Container designed to support practically any type of video or audio stream you might care to use. MKV stands for Matroska Video. The project itself is simply called Matroska.
Rather than being designed around a particular format's capabilities, Matroska's container simply provides a framework to mux and interact with audio, video, and even subtitle streams. Video commonly found in the Matroska container includes RealVideo, XviD, and more recently AVC. Audio ranges from Vorbis (OGG) to MP3 or even the original AC-3 audio from a DVD. Matroska files will sometimes have an extension of .MKA instead, indicating an audio only file - typically encoded in the Vorbis format.
Interactivity
With the container fairly well established, the next major goal of the Matroska project is to establish interactive playback similar to commercial formats like DVD, but utilizing an open source XML based language called EBML, which stands for Extensible Binary Markup Language. In addition, the group is hoping to establish hardware support among consumer electronics vendors, which seems more likely every day with AVC steadily gaining in popularity, and MKV being the primary container used for storing AVC video with AC-3 (Dolby Digital) audio.
Reading MKV Files
Some containers are either tied to a particular operating system, like the Windows AVI or common enough to be widely supported by common media players or even operating systems, like the MPEG-2 Program Stream. If you're using a program like VLC, where container support is built into the player, no additional software should be necessary. If you're using software like ffdshow or any standard (Windows) DirectShow decoder you'll need additional software for splitting MKV files.
Haali Media Splitter
The process of playing back video and audio from any container starts with splitting the different streams and sending them to the appropriate software (or hardware) for decoding. Different operating systems and third party software may include support for less established containers like MP4. For MKV files you'll need to install the Haali Media Splitter. Conveniently, if you have MP4 files you need to extract one or more streams from (such as Muxing the video along with a DVD's original AC-3 audio to a MKV file) the Haali Media Splitter handles both. It doesn't include any Codec support though, so you may need additional software, such as ffdshow, to actually play the contents of a MKV file.
Playing MKV Files
In our Guides section you'll find a guide titled How to play MKV files. As the name suggests, it covers computer-based playback of MKV files. You may also find our guide on How to play MP4 files useful if you need to extract streams from that container to mux into a Matroska file. If you have MKV files with AVC video that you want to play on a PS3 you can use our guide How to play mkv files with x264 video and AC3 audio on the Sony PlayStation 3.
VLC
For the simplest possible playback solution, and one that's cross-platform as well, you can use VLC. It has its own Matroska splitter, so it requires no additional software, including the Haali Media Splitter.
AVC
It's recently become quite common to see AVC (H.264 / MPEG-4 Part 10) video stored in the MKV container. One reason for this is an initial lack of an official container for AVC which wasn't standardized until MPEG-4 Part 14. As many video enthusiasts were anxious to cut the ties to Windows created by the AVI container, MKV became an alternative. Although support for the MP4 format has become fairly common, and in fact supported by the same splitter used for MKV, it hasn't gained universal acceptance. For decoding the AVC video you can either use a commercial decoder, such as CoreAVC, or the free ffdshow decoder.
XviD
XviD is also often seen in a Matroska Container. Like AVC this is often motivated by the need for support on non-Windows platforms such as Linux. It can also be handled by ffdshow.
RealVideo
At one time RealVideo was a de facto standard for anime fansubs, which have been used by anime fans to distribute movies and TV shows to areas where they aren't otherwise available. RealVideo became popular because of its (then) superior quality at exceedingly low bitrates. The instructions in our guide titled How to play RMVB files will help you install the necessary software to play RealVideo in your MKV files.
Audio Support
One advantage to Matroska's universal container approach is that audio doesn't need to be transcoded into a preferred or official format.
AC-3
Many Matroska files contain AC-3 audio, particularly accompanying AVC video. Since most software won't playback AC-3 (Dolby Digital) from the MP4 container, the easiest solution for many people is to simply use the Matroska containter, which has no problems combining AVC and AC-3.
Vorbis
The Ogg Vorbis format is sometimes used for MKA audio files, or even to Encode audio for MPEG-4 encoded movies. Vorbis is a patent-free (ie royalty-free) audio format, similar to MP3 or AAC. Due to a lack of exposure to the format by the general public, this is probably the least popular audio format found in MKV files.
AAC
Many Matroska files contain AAC audio, generally in combination with AVC video.
Subtitles
It's possible to adapt just about any subtitle format to be used in a MKV file. Standard formats like SRT and VobSub are common.
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Creating MKV Files
The tool generally preferred for Muxing streams into MKV files is called mkvtoolnix. It actually contains tools for extracting streams from MKV files, muxing streams to create them, and even getting basic information on them.
Playback Guides
How to play MKV files
How to play RMVB (RealMedia Variable Bitrate) files
How to play mkv files with x264 video and AC3 audio on the Sony PlayStation 3
Encoding From MKV
Convert MKV to DVD with freeware
