As a Windows Media Center Extender, the Echo is limited to containers that Windows Media Center can handle. In fact, a Windows Media Center Extender doesn't deal with containers at all, which is why they have not been included in our specification list. Out of the box, Windows Media Center does not support the MKV container; however, there are several third-party solutions available that add support to WMC for the MKV container. We’ve provided a list of codecs that the Echo will support at launch in the Tech Specs section of the Echo product page. If your Windows Media Center PC has been configured to handle the MKV container, and the codecs within the container are also supported by the Echo, it should be possible to play that content back on the Echo.