Video overlay
（重定向自Overlay card）
Video overlay is any technique used to display a video window on a computer display while bypassing the chain of CPU to graphics card to computer monitor. This is done in order to speed up the video display, and it is commonly used, for example, by TV tuner cards and early 3D graphics accelerator cards. The term is also used to describe the annotation or inclusion of interactivity on online videos, such as overlay advertising (mid-roll overlay).