If you are trying to create an AR experience with this file, tools like Adobe Express can help ensure the MP4 is optimized for web-based AR triggers.
The "AR" prefix often refers to Advanced Recording Format (.arf) used by Cisco Webex. Since yours is an MP4 , it has likely already been converted from its original meeting format to be playable on standard devices. AR 00103b mp4
Most AR platforms recommend avoiding full-frame pure black at the start to prevent "blank" triggers. How to Manage the File If you are trying to create an AR