: Many generic DVR/NVR systems use alphanumeric strings. If you found this on an SD card, it is likely a motion-triggered event.
If you downloaded this file from an untrusted source or a "mystery link":
: The prefix "G" followed by numbers is a standard naming convention for some 70mai dashcam models (like the G500 or G150 series). The "G150.mp4" file is likely a saved video segment from your car's camera.
: Most proprietary camera formats use H.264 or H.265 codecs. VLC is the most reliable tool for opening these without needing extra plugins.