RG82855GMESL72L Datasheet, PDF (152/213 Pages) Intel Corporation – Intel® 855GM/855GME Chipset Graphics and Memory Controller Hub (GMCH)

Functional Description
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6.4.7.3
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6.4.7.5
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6.4.8
6.4.8.1
Gamma Correction
To compensate for overlay color intensity loss, the overlay engine supports independent gamma
correction. This allows the overlay data to be converted to linear data or corrected for the display
device when not blending.
YUV to RGB Conversion
The format conversion can be bypassed in the case of RGB source data.
Color Control
Color control provides a method of changing the color characteristics of the pixel data. It is
applied to the data while in YUV format and uses input parameters such as brightness, saturation,
hue (tint) and contrast. This feature is supplied for the overlay only and works in YUV formats
only.
Dynamic Bob and Weave
Interlaced data that originates from a video camera creates two fields that are temporally offset by
1/60 of a second. There are several schemes to de-interlace the video stream: line replication,
vertical filtering, field merging, and vertical temporal filtering. Field merging takes lines from the
previous field and inserts them into the current field to construct the frame – this is known as
weaving. This is the best solution for images with little motion; however, showing a frame that
consists of the two fields will have serration or feathering of moving edges when there is motion
in the scene. Vertical filtering or “Bob” interpolates adjacent lines rather replicating the nearest
neighbor. This is the best solution for images with motion however, it will have reduced spatial
resolution in areas that have no motion and introduce jaggies. In absence of any other de-
interlacing, these form the baseline and are supported by the GMCH.
Video Functionality
The GMCH supports MPEG-2 decoding hardware, sub-picture support and DTV.
MPEG-2 Decoding
The GMCH MPEG2 Decoding supports Hardware Motion Compensation (HWMC). The GMCH
can accelerate video decoding for the following video coding standards:
• MPEG-2 support
• MPEG-1: Full feature support
• H.263 support
• MPEG-4: Only supports some features in the simple profile
The GMCH HWMC interface is optimized for Microsoft’s* VA or API. Hardware Video
Acceleration API (HVA) is a generic DirectDraw and DirectShow interface supported in
Windows XP, Windows 2000 and Windows 98 Millennium to provide video decoding
acceleration. Direct VA is the open standard implementation of HVA, which is natively supported
by the GMCH hardware.
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Datasheet