Video Compression > Video Containers

Matroska FAQ

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Kovensky:
1) What is matroska? I have heard it is a "container format"? What's that?
A container format allows you to combine different multimedia streams (most of the time audio and video) into one single file.
Multimedia containers are for example the well known AVI (.avi), MPEG (.mpg, .mpeg), OGM (.ogm), MP4 (.mp4) or Realmedia (.rm, .rmvb)

The matroska project is a free, opensource container format, aiming to be able to offer a lot of advanced features, which older formats like AVI can't handle, on an extensible basis.
Matroska supports for example the storage of Variable Bitrate audio content (VBR) without any hassles, Variable Framerates (VFR), Chapters, attachment of files, Error Detection (EDC) and modern A/V Codecs like H.264, VC-1, AAC, FLAC, Vorbis, TrueHD, which are next to nothing handled by AVI.

2) What extensions is matroska using?
- .mkv: generally video files (with or without audio)
- .mka: audio only files, can contain any supported audio format, such as MP2, MP3, Vorbis, AAC, AC3, DTS...
- .mks: a so called "elementary" matroska stream, containing any subtitles stream

3) How can i create matroska files?
With the following tools you can create or edit matroska files (for example transmux from exisiting AVI files):
- MKVtoolnix includes the mkvmerge commandline tool (+ gui), can mux vobsub subtitles!
- AVI-Mux GUI
- AviDemux. Note: last time I checked this had problems with b-frames.
- FFmpeg. Windows builds are available on http://ffmpeg.arrozcru.org/autobuilds/.
- AutoMKV
- Graphstudio, advanced users can also use gabest's matroska muxer filter
- There's also VirtualDubMod. Do NOT use this.

4) Does transmuxing to matroska reencode the content?
No, this is a lossless process, only taking out the media streams from one container and putting them into matroska

5) After appending/joining two matroska files in VirtualDubMod, the output seems to have some failures?
Do NOT use VirtualDubMod.

6) Are my now created matroska files going to be compatible with future matroska implementations?
Yes, files being created now are fully spec compliant. in fact matroska is based on a very flexible underlying framework called EBML, which allows to add more functionalities to the container format in the future (for example new A/V codecs, DVD-like menus) without breaking backwards compatibility with older software and files.

7) How can i play matroska files on Windows?
The Matroska team recommends the Combined Community Codec Pack for playing back matroska files.

8) How can i play matroska files on Linux, MacOS and X-Box?
you have to get the newest version of mplayer, for file creation/editing you find everything you need on Mosu's site. There is also a Gstreamer plugin by Ronald 'BBB' Bultje, which you can find in the GStreamer CVS

9) Does Matroska need more Processor Power than AVI?
No, you can't tell a difference while reading back AVI or Matroska content on today's processors. Writing currently takes more, but that is mostly because time is needed to refine the writing apps for MKV.

10) What subtitle types can be muxed into matroska? How can i play them?
Currently SRT, SSA, ASS and VobSub
Use gabest's VSFilter to play subs on DShow based players

11) Why are some matroska files created from AVI smaller than the source itself?
Because matroska needs less overhead than the AVI container (especially with VBR-MP3)
You can find a nice overhead comparison by alexnoe here

12) Is it possible to create variable frame rate (VFR) content in matroska?
Yes, through the use of timecodes files. Tutorials for that should follow shortly.
AVI-Mux GUI can also join AVI files with different framerates into a matroska file.
There also was a project working on vfr-encoding, called Variable Framerate Encoder. They released an app which lets you join vfr AVIs. (EDIT: link removed since it was broken, couldn't find a better one through google :()

13) Does Matroska support "anamorphic resize"?
Yes, you can set the display size of your matroska files for example in mkvmerge, AVI-Mux GUI or in your windows explorer by using the matroska shell extension. (EDIT: link removed, was broken and couldn't find a better one with google)

14) What is the advantage of putting audio only into .mka?
Read more about what can be possible at matroska.org.
Currently it is already possible to store a whole CD as 1 track in mka, each song seperately choosable and tagged and you can already play it in any DShow based player or in foobar2000.

15) Does Matroska support multi-angle video files (multiple video streams in one matroska file)?
Yes, you can create such files with gabest's mkv muxer in graphedit or mkvmerge. Playback works with Haali's mkv splitter in directshow.

16) How can i create Chapter files in the Matroska XML format?
Notepad ;)
There's AutoMKVChapters, a program for generating chapters based on templates + avisynth scripts with trim commands.
The mkvmerge GUI also supports making chapters, but doesn't support ordered chapters.
You can also use Toff's ChapterXtractor for that, read more here.

17) How can i convert from Matroska to another format? for example to AVI/MPEG?
Why would you want to do that? :)
You can use GDSMux if you really need to, as pointed out by CryptWizard.

18) I want to read more about matroska! Where can i find more info?
Feel free to visit the official matroska homepage at matroska.org, there you'll find much more information, as this sticky is only meant as a starting point for newbies to handle matroska

CryptWizard:

--- Quote ---17) How can i convert from Matroska to another format? for example to AVI/MPEG?
Why would you want to do that? :)
--- End quote ---

I've very often heard of people re-encoding to XVID just to load a video in After Effects.

It would be much more helpful to just let them know they can use GDSMux.

Kurtnoise:
@Kovensky: why you are copying D9 stickies ? this Matroska FAQ must be updated imo...

Dark Shikari:

--- Quote from: Kurtnoise on December 03, 2009, 12:41:35 AM ---@Kovensky: why you are copying D9 stickies ? this Matroska FAQ must be updated imo...


--- End quote ---
Feel free to post an updated version and I'll delete the old one  ;)

Kovensky:

--- Quote from: Kurtnoise on December 03, 2009, 12:41:35 AM ---@Kovensky: why you are copying D9 stickies ? this Matroska FAQ must be updated imo...

--- End quote ---
Indeed it should; I already changed some bits and pieces but if you have more changes, do as D_S said.

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