Implementations in Various Operating Systems
Windows Vista's enhanced graphics capabilities replace the basic concept of hardware overlays with full hardware compositing for every application window running on the system, not just movie players or games, through the Desktop Window Manager. Mac OS X has used hardware compositing since the introduction of Quartz Extreme into Mac OS X 10.2. To improve performance, each program draws to its own independent memory buffer instead of to a slow graphical subsystem. (In Windows Vista, each hardware overlay is more correctly known as a Direct3D surface). Then the system's GPU assembles each of the windows into a single display screen in real time. With enhanced GPUs on the market capable of stunning 3D graphics (as a consequence of the video game industry), operating systems can apply impressive motion, scaling, and lighting effects to normal 2D windows.
In the X Window System, the windowing system of most Unix operating systems, the XVideo extension can allow applications to employ hardware overlays. Compositing is also used, with compiz and Beryl compositing window managers being the most prominent examples since 2006. They are able to take advantage of OpenGL (through glx extension) for 3D and 2D overlay visual effects. Other implementations like Metacity and xfwm have been available since 2004.
Some dedicated hardware overlay devices use embedded Linux as an operating system, for example the video logger by Racelogic uses a Texas Instruments DM355 micro-controller to blend a frame buffer containing graphics onto a live video feed, and then store the result in MPEG-4 format on a flash card.
Overlay support aka Picture In Picture (PIP) was introduced to AmigaOS with the introduction of the PC graphic cards, Picasso96 and Cybergraphix graphic driver systems aka ReTargetable_Graphics, for Picasso IV and Voodoo3 cards, picasso’96 driver system became standard in AmigaOS 3.5, Moovid was one of the first video players that supported hardware overlay (PIP) on AmigaOS.
Read more about this topic: Hardware Overlay
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