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:
To help me provide a useful report, could you clarify the context of this file? For example: AgADCQgAAjVlyVY.mkv
(e.g., Was it sent in a specific Telegram group or found on a hard drive?) Based on the alphanumeric string (e