K-720p-hd-21-jan-mkv -

: The date the file was aired, released, or ripped (January 21st).

Could you please clarify or platform you are referring to so that I can provide a more tailored answer? Unable to play some mkv files to WD TV Live k-720p-hd-21-jan-mkv

The string appears to be a specific video file name or a standard pirate scene release tag rather than a widely cataloged media topic. : The date the file was aired, released,

: Often indicates the initials of the uploader, the group that encoded the video, or the language (such as Korean). 720p : The video resolution ( hd : Stands for High Definition. : Often indicates the initials of the uploader,

: If the file plays audio but no video (or vice versa), try using a versatile player like VLC Media Player or MPC-HC that handles advanced .mkv containers natively.