Video Rendering Filters
Originally, in Windows 9x, DirectShow used the Video Renderer filter. This drew the images using DirectDraw 3, but could also fall back to GDI or overlay drawing modes in some circumstances (depending upon the visibility of the video window and the video card's capabilities). It had limited access to the video window. Video for Windows had been plagued with deadlocks caused by applications' incorrect handling of the video windows, so in early DirectShow releases, the handle to the playback window was hidden from applications. There was also no reliable way to draw caption text or graphics on top of the video.
DirectShow 6.0, released as part of DirectX Media introduced the Overlay Mixer renderer designed for DVD playback and broadcast video streams with closed captioning and subtitles. The Overlay Mixer uses DirectDraw 5 for rendering. Downstream connection with the Video Renderer is required for window management. Overlay Mixer also supports Video Port Extensions (VPE), enabling it to work with analog TV tuners with overlay capability (sending video directly to a video card via an analog link rather than via the PCI bus). Overlay Mixer also supports DXVA connections. Because it always renders in overlay, full-screen video to TV-out is always activated.
Windows XP introduced a new filter called the Video Mixing Renderer 7 (VMR-7 or sometimes just referred to as VMR). The number 7 was because VMR-7 only used DirectDraw version 7 to render the video and did not have the option to use GDI drawing. The main new feature of VMR-7 was the ability to mix multiple streams and graphics with alpha blending, allowing applications to draw text and graphics over the video and support custom effects. It also featured a "windowless mode" (access to the composited image before it is rendered) which fixed the problems with access to the window handle. VMR-7 was only officially released for Windows XP.
DirectX 9 included VMR-9. This version uses Direct3D 9 instead of DirectDraw, allowing developers to transform video images using the Direct3D pixel shaders. It is available for all Windows platforms as part of the DirectX 9 redistributable. As VMR-7 it provides a Windowless Mode. However, unlike Overlay mixer or VMR-7 it does not support video ports. Using the /3GB boot option may cause VMR-9 to fail.
Windows Vista and Windows 7 ship with a new renderer, available as both a Media Foundation component and a DirectShow filter, called the Enhanced Video Renderer (EVR). EVR is designed to work with Desktop Window Manager and supports DXVA 2.0, which is available on Windows Vista and Windows 7. It offers better performance and better quality according to Microsoft.
Read more about this topic: DirectShow
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—Ronald Reagan (b. 1911)
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