I've always been curious on how it works; It could be anything ranging from a video file (which is very unlikely), to an animation being rendered in real time by the console. Any Xbox 360 experts who know how bootanim.xex does its magic? Thanks!!!
bootanim.xex on Xbox 360 is a real-time rendered 3D animation, not a video file. It’s an executable the kernel runs early in boot to display the Xbox 360 logo and play the startup sound using the console’s GPU and audio system. After the short animation finishes, it exits and the dashboard (dash.xex) loads.