The prefix is the standard naming convention used by Apple iOS devices (iPhone and iPad) and many digital cameras (such as Canon) to label image and video assets.
If you have this specific file and are unsure of its contents, you can use the following methods to identify its details without playing it: IMG_69411.mp4
If "IMG_69411.mp4" is part of a specific you recently encountered, providing more context about where you saw the name would help in identifying its specific narrative significance. How to Create and Open an MP4 File The prefix is the standard naming convention used