{{Distinguish, on-screen display Video overlay is any technique used to display a

video Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) sy ...

window on a computer display while bypassing the chain of

CPU A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, a ...

graphics card A graphics card (also called a video card, display card, graphics adapter, VGA card/VGA, video adapter, display adapter, or mistakenly GPU) is an expansion card which generates a feed of output images to a display device, such as a computer mo ...

computer monitor A computer monitor is an output device that displays information in pictorial or textual form. A discrete monitor comprises a visual display, support electronics, power supply, housing, electrical connectors, and external user controls. The ...

. 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). Various methods to achieve video overlay are in use: * A video overlay device can be connected between the graphics card analog

VGA Video Graphics Array (VGA) is a video display controller and accompanying de facto graphics standard, first introduced with the IBM PS/2 line of computers in 1987, which became ubiquitous in the PC industry within three years. The term can now ...

output and the monitor's input forming a "VGA passthrough". The device modifies the VGA signal and ''inserts'' the analog video signal overlay into the picture; the rest of the screen is filled by the signal coming from the graphics card. The driver software informs the video overlay device about the desired position of the video window on screen. Because of the much greater processing power of modern graphics cards, and the awkwardness of adding additional analog hardware signal processing path, this method is now little used. * Some video overlay devices write the digital video signal directly into the graphics card's

video memory Dynamic random-access memory (dynamic RAM or DRAM) is a type of random-access semiconductor memory that stores each bit of data in a memory cell, usually consisting of a tiny capacitor and a transistor, both typically based on metal-oxid ...

or provide it to the graphics card's RAMDAC. * Hardware overlay is a technique implemented by most modern graphics cards that allows an application to write to a dedicated part of video memory, rather than to the part shared by all applications. In this way, clipping, moving and scaling of the image can be performed by the graphics hardware rather than by the CPU in software. Some solid state video recording systems now include a hardware overlay, which uses dedicated video processing hardware built into the main processor (for example the Texas Instruments DM355) to combine each frame of video with an area of memory configured as a

frame buffer A framebuffer (frame buffer, or sometimes framestore) is a portion of random-access memory (RAM) containing a bitmap that drives a video display. It is a memory buffer containing data representing all the pixels in a complete video frame. Mode ...

which is used to store the graphics. * Overlay advertising is a technique used by online video producers to monetize video content through using an overlay layer to deliver and display an ad unit. This can be in the form of a video advertisement,

hypervideo Hypervideo, or hyperlinked video, is a displayed video stream that contains embedded, interactive anchors, allowing navigation between video and other hypermedia elements. Hypervideo is thus analogous to hypertext, which allows a reader to click o ...

a product placement or a contextual link, clickable graphic or text that provides information related to the content of the video and/or the target of the link being placed.

See also