It is expected that the Windows 10 OS will be compatible with MKV, HEVC and FLAC video formats but it appears that Microsoft does does not want to wait for its next OS and has brought this feature to Windows 8.1 store.
With the Technical Preview of Windows 10, it was discovered that Microsoft had added support for multiple codecs to its Windows Media Player. Today, the Windows 8.1 is entitled to a similar treatment.
This is not for Windows Media Player, but the Video application available at Microsoft Store and which launches automatically when you want to watch a movie. An update released yesterday made it compatible with MKV format, even if FLAC is not yet supported and some soundtracks may not work.
It is just an automatic update away and your PC running on Windows 8.1 OS or your Xbox One will allow you to play a movie in MKV format without having to go through a third-party software.
Source:
Le Comptoir du Hardware.