If you're having trouble playing it, the VLC Media Player is a great "universal" choice that handles most codecs.
It sounds like you've found a solid video file! While I don't have direct access to private files named , that specific naming convention (often starting with "YI") is common for files generated by Yi Technology cameras, such as their popular action cams or home security systems.
If you're looking to view or edit it, the MP4 format is widely compatible across almost all modern devices.
Since MP4s offer a good balance of quality and compression , they are ideal for sharing on social media or keeping in cloud storage without taking up too much space.
What was the "good piece" of—a cool action shot, a security catch, or something else? VLC for Android – Apps on Google Play