Cover.mp4

This is a massive, unprocessed file (often 1GB for every 30 seconds of 4K footage). This file contains the high-dynamic-range data that Google's servers use to "boost" the video's lighting, stabilization, and color. How the Process Works: Upload: Google Photos uploads both files to the cloud. Processing: The "Boost" happens on Google's servers.

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

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. This is a massive, unprocessed file (often 1GB

It is a generic filename often used by artists or creators for a video cover of a song (e.g., "Misty Cover.mp4"). Processing: The "Boost" happens on Google's servers

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.

Users often find these files when manually backing up their phones or using third-party file managers. If you see a COVER.mp4 file and notice it looks lower quality than expected, it simply means the "Boost" hasn't finished processing or syncing yet.