Because it is a generic file name or part code, it most likely refers to one of the following:
If the video won't play, use a universal player like VLC Media Player to bypass common codec issues. b031.mp4
It is used as a suffix for memory chips, such as the Samsung eMMC Storage Chip Go to product viewer dialog for this item. Because it is a generic file name or
Did you find this file on a (like a dashcam) or a website , or b031.mp4
If you have a file with this specific name and cannot open it:
(KLMBG4WEBD-B031), which is commonly used in notebooks and mobile devices.