Agadcqgaajvlyvy.mkv [ WORKING ]

(e.g., Is it a security recording, a lecture, or a personal video?)

(e.g., Was it sent in a specific Telegram group or found on a hard drive?)

Based on the alphanumeric string (e.g., "AgADC..."), this looks like a often used by messaging apps (like Telegram ) or cloud storage platforms to name uploaded files. What you can do next: