03-37-54.mkv | 2021-08-07

Since .mkv is a flexible container, VLC is the most reliable tool to play it regardless of the internal codecs.

The filename appears to be a default timestamp-based name typically generated by recording software like OBS Studio , ShadowPlay , or security camera systems . 2021-08-07 03-37-54.mkv

If the video won't play, it may be a "broken" recording (common if OBS crashed during the 3:37 AM session). You can try using Untrunc or FFmpeg to repair the header. Since .mkv is a flexible container