The player supports MKV files containing files in the official Blu-ray format. However, if the MKV file contains any file that is not using the official blu-ray requirements, there may be playability issues. MKV is a file container format that can hold a number of files inside a single file. The files can be audio, video, picture or subtitle. We can imagine MKV as an envelope, containing video, audio and subtitle information inside one single place. Therefore, the different files for one complete movie are neatly contained in a single MKV file. Most of the Blu-ray players in the market apply the industrial standard of video compression H.264 . This standard allows the player to support video files of profile up to Level 4.1 . Therefore, if the MKV file contains video files of profile higher than Level 4.1, playability problem may result. Checking the profile level of the video files inside the MKV file The profile level of the video files inside a MKV file cannot be checked with a few clicks. There are some tools known as ?File Information Tools? available in the internet that allows consumers to check this information. For more information, visit the MKV Matroska internet website. Changing the profile to make the MKV files be supported by the player Profiles define the sets of bit stream features the h.264 stream can use. Levels define restrictions on the video resolution, frame rate and VBV (Video Buffer Verifier) etc.. In short, Level 5.1 uses four to five times the bandwidth of Level 4.1 and hence allows very high definition video, 4096×2304@25 or similar. If the MKV file contains video files of profile higher than Level 4.1, you can make use of tools known as ?MKV Conversion Tools? available in the internet to change the profile.