"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.
When you record a video with enabled on a compatible Google Pixel device, your phone doesn't just create one file. Instead, it creates a "dual-file" system to balance immediate usability with high-end processing: Cover.mp4
When using the Video Boost feature on Pixel phones, the device generates a temporary file named COVER.mp4 . This is a low-resolution (1080p) preview that you can view immediately while the high-quality version is being processed in the cloud. "Cover