Stream MP4 file over usb

I have an embedded system running a custom distro built using Yocto. Later down the line, I will have a usb camera plugged into the system, but for not I would like to use a .mp4 file as a "dummy" camera. My goal is to stream the video file over USB as a USB UVC device to a computer so that the computer sees my embedded Linux system as a USB webcam: I can't find any documentation on the subject and I am a bare metal c developer dipping his toes into embedded Linux development. I would like to know what to look for and the broader steps to get this working. (including modifications to the distro through Yocto.) Thank you.