It is a generic filename often used by artists or creators for a video cover of a song (e.g., "Misty Cover.mp4").
Once the boosted version is ready, Google Photos downloads the final high-quality version and typically deletes the massive raw MAIN.mp4 to save space. Cover.mp4
While it could refer to any of these, I am providing a text focused on the context, as it is a specific technical term associated with that filename. Understanding COVER.mp4 in Google Pixel Video Boost It is a generic filename often used by
"Cover.mp4" is a common placeholder or filename used by developers for a background video or a video used as a "hero" element on a website or splash screen. Cover.mp4