301467-005 Datasheet, PDF (244/426 Pages) Intel Corporation – Express Chipset

Functional Description
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destination. Transparent transfers compare destination color to source color and write according
to the mode of transparency selected.
Data is horizontally and vertically aligned at the destination. If the destination for the BLT
overlaps with the source memory location, the GMCH can specify which area in memory to begin
the BLT transfer. Hardware is included for all 256 raster operations (Source, Pattern, and
Destination) defined by Microsoft, including transparent BLT.
The GMCH has instructions to invoke BLT and stretch BLT operations, permitting software to set
up instruction buffers and use batch processing. The GMCH can perform hardware clipping
during BLTs.
12.6.6 Video Engine
12.6.6.1
12.6.6.2
Hardware Motion Compensation
The Motion Compensation (MC) process consists of reconstructing a new picture by predicting
(either forward, backward, or bi-directionally) the resulting pixel colors from one or more
reference pictures. The GMCH receives the video stream and implements Motion Compensation
and subsequent steps in hardware. Performing Motion Compensation in hardware reduces the
processor demand of software-based MPEG-2 decoding, and thus improves system performance.
The Motion Compensation functionality is overloaded onto the texture cache and texture filter.
The texture cache is used to typically access the data in the reconstruction of the frames and the
filter is used in the actual motion compensation process. To support this overloaded functionality
the texture cache additionally support the YUV420 planar input formats.
Sub-Picture Support
Sub-picture is used for two purposes; one is Subtitles for movie captions, etc. (that are
superimposed on a main picture), and the other is Menus used to provide some visual operation
environments the user of a content player.
DVD allows movie subtitles to be recorded as Sub-pictures. On a DVD disc, it is called "Subtitle"
because it has been prepared for storing captions. Since the disc can have a maximum of 32 tracks
for Subtitles, they can be used for various applications, for example, as Subtitles in different
languages or other information to be displayed.
There are two kinds of Menus; the System Menus and other In-Title Menus. First, the System
Menus are displayed and operated at startup of or during the playback of the disc or from the stop
state. Second, In-Title menus can be programmed as a combination of Sub-picture and Highlight
commands to be displayed during playback of the disc.
The GMCH supports sub-picture for DVD and DBS by mixing the two video streams via alpha
blending. Unlike color keying, alpha blending provides a softer effect and each pixel that is
displayed is a composite between the two video stream pixels. The GMCH can use four methods
when dealing with sub-pictures. The flexibility enables the GMCH to work with all sub- picture
formats.
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Datasheet