The ".mp4" extension (MPEG-4 Part 14) is a digital multimedia container format used to store video, audio, and even subtitles.
Many surveillance systems use four-digit codes for continuous recording clips. 5394mp4
The "5394" is typically a sequential number assigned by a camera’s firmware. For example, some dash cams or action cameras name files sequentially (e.g., 5392.mp4, 5393.mp4, 5394.mp4). Common Origins 5394.mp4). Common Origins