Windows 10 Natively Supports FLAC and MKV Codecs
 

It looks as though Windows 10 will feature support for MKV and FLAC right out of the box. This expands Microsoft's support for popular but less-than-standard file formats. FLAC joins MKV (one of the most common containers for H.264 video alongside MP4) and HEVC (High Efficiency Video Coding), both of which were also confirmed by Aul on Twitter last month.

http://www.hardocp.com/news/2014/11/...ac_mkv_codecs/