Microsoft KB Archive/120260

Display Control Interface DDK

PSS ID Number: Q120260 Article last modified on 06-20-1995

1.00

WINDOWS

= Product Description =

The Display Control Interface (DCI) for the Microsoft Windows operating system is a driver-level software interface that provides access to display devices while maintaining compatibility with Windows GDI. DCI works with Windows 95 and Windows 3.1.

NOTE: A newer version of the DCI spec will be provided to address the Windows 95 aspects and implementation.

DCI provides a device-independent way for Windows subsystem software, such as 3-D graphics packages, games interface packages, or digital video codecs, to access display device-dependent features. In the case of digital video codecs, additional support is provided so that any codec that already supports the ICM_DECOMPRESSEX message as specified by the Video for Windows Installable Codec Interface automatically takes advantage of DCI capabilities, if these capabilities are available.

DCI works with a wide variety of display hardware, ranging from simple SVGAs to advanced hardware implementations containing clipping, stretching, and non-RGB color format support. The interface is designed so that DCI clients can request the capabilities of the underlying hardware, then use the capabilities as required. Cards that use chipsets that don’t support access to the frame buffer by the host are not supported by the DCI Specification.

DCI provides access to the following display device-dependent benefits:


 * Improved video playback quality through access to YUV color formats
 * Improved graphics and video quality through access to image-stretching hardware
 * Support for double-buffered graphics
 * Simultaneous access to standard and enhanced display device memory areas
 * Smooth rendering of 3-D graphics
 * Graphics overlaid on video in a window

The interface is not designed to provide access to software running on coprocessors that require display capabilities; typically these designs feature hardware-specific interfaces from the coprocessor to the display, so no Windows-based software is used to put pixels on the display. For example, video coprocessors, such as the Intel i750 processor or MPEG decompression processors, typically provide, their own hardware-specific drivers. If these coprocessors pass data back to Windows subsystem software, then DCI may be used.

= Windows NT Considerations =

DCI support under the Windows NT operating system is not addressed by this document. DCI relies on the ability to directly access and draw on display memory. Windows NT display memory is not exposed the same way as Windows 3.1. A special solution is being worked on.

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Copyright Microsoft Corporation 1995.