In the (Defense Visual Information Distribution Service) database, ID 125996 corresponds to historical military footage.
Based on current digital databases, here are the most likely possibilities for what the file contains: 1. 127 Hours (Film) 125996.mkv
The ID 125996 is assigned to a specific educational video lesson on (rise over run) from Talbert Middle School. 125996.mkv
This is typically a default naming convention for automated uploads or security camera exports. 125996.mkv
A high-energy musical performance titled "Piyar Karab Tohar Lahanga Sadi Ho." 4. Technical or Military Footage
If this is a movie file, it is almost certainly a high-definition copy of Danny Boyle's survival drama about Aron Ralston.