Datasheet

Functional Description
R
192 Datasheet
5.4.7.5 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.
5.4.7.6 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.
5.4.8 Video Functionality
The GMCH supports MPEG-2 decoding hardware, sub-picture support and DTV all format
decode.
5.4.8.1 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 the Microsoft Direct VA* API. Hardware Video
Acceleration API (HVA) is a generic DirectDraw* and DirectShow* interface supported in
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.
5.4.8.2 Hardware Motion Compensation
The Hardware Motion Compensation (HWMC) process consists of reconstructing a new picture
by predicting (either forward, backward, or bi-directional) 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.