How to Convert MP4 to 4K UHD Fast and Effortlessly?
GitHub - chthomos/video-media-samples: Three different versions (480p, 1080p, 1080p@60fps) of mp4 encoded (H264/AAC) 30 seconds version of Big Buck Bunny for test with browser media
Big list of sample videos for testers - standaloneinstaller.com
Sample Videos, Download The BEST Free 4k Stock Video Footage & Sample HD Video Clips