Can we use mp4 backgrounds in Immersive view?

Hi all, seeking info/advice on custom Immersive View backgrounds. I'm trying to select a 1920x1080 mp4 for the background, but all movie files are grayed out in the finder...Zoom will only let me select jpgs. However, in Zoom's Immersive View support article it states that Immersive View backgrounds just need to follow the Virtual Background specs, which do allow video, and I'm able to use an mp4 for my Virtual Background with no problem. Does anyone have any info/experience with getting video backgrounds to work in Immersive View?  Thanks in advance for any guidance!