Complete name : \test2013.1080p.x264.AAC.mkv
Format : Flash Video
1st thing i would try, is renaming it to flv (since the format says Flash Video)
2013.1080p.x264.AAC. flv
2nd thing (if that doesent work) try remuxing it using MKVMerge ( MKVToolnix)
(and alternatly (if that doesent work) you could use FLV Extract then remux the video/audio streams with MKVMerge)