MX86251 データシートの表示（PDF） - Macronix International
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MX86251 Datasheet PDF : 32 Pages
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MX86251
showed that about one third time each is spent in de-
compression, color conversion and pixel transfer to
screen. The Video Processor implements the color con-
version and pixel transfer in hardware, leaving only the
decompression task to CPU. Thus, the video play frame
rate which used to be 8 to 10 fps from software Codec is
approximately tripled to the full motion rate of 30 fps by
the MX86251.
Video clips are typically in QCIF or CIF format which are
relatively small when viewed on the SVGA display. It is
very desirable to scale up the video window to at least
640x480 or even full screen at 1024x768. The scale up
can be just duplicating the pixels (Zoom) which produces
blocky pictures. In high end broadcast quality video pro-
cessing, a smoothing filter is typically used to remove
the blocky artifacts.The MX86251 Video Processor imple-
ments both Scaler and smoothing Filters so that full mo-
tion video can play in full screen without degradation.
Horizontal and Vertical interpolation
The Video Processor performs the filtering in both Hori-
zontal and Vertical dimension. While most first genera-
tion Video chips only have one horizontal filter. The
MX86251 provides three filters to fit the particular needs
of different video decoders. The vertical interpolation fil-
ter further enhances the appearance of video images by
eliminating staircasing diagonal lines and illegible text
commonly seen in video played by 1st generation video
chips.
Pixel formats
The Video Processor supports many pixel formats. The
Video pixels can be in RGB formats such as KRGB-
1.5.5.5, RGB-5.6.5, XRGB-8.8.8. The KRGB has 1 key
bit which works as a color key. More likely, the video pix-
els are in YUV format such as YUV-16 (4:2:2), YUV-8
(2:1:1), or YCbCr-16 (4:2:2). The YUV format pixel has a
range of value from 0 to 255, while the YCbCr format
pixel values are in the range of 16 to 240.
Direct Draw feature support
The Chroma key is designed for Blue Screen video which
is very useful in games where video sprites are employed.
The new Indeo 4.0 transparency feature also makes
heavy use of the Chroma key mechanism.
The video window can be double-buffered to avoid tear-
ing. The Video Processor executes page flipping in syn-
chronization with Vertical blanking. A status bit is pro-
vided to inform software of the completion of page flip-
ping.
Edge Blending
The MX86251 "edge blending" is an unique new feature.
It is implemented to enhance the edge quality of Chroma
keyed video sprites. DirectDraw does provide API calls
which support the use of edge blending.
The Blending feature provides 16 levels of alpha mixing
of the video and graphics window. This can be used to do
a very smooth dissolve or fade which are popular visual
effects often used in edutainment titles.
2.6 Media Port
The Media Port is a direct interface to MPEG and Video
decoders. A MX86251 based graphics card can deliver
very extensive multimedia functionality by fully utilizing
the Media Port. An MPEG-1 decoder chip can be incor-
porated on board to deliver higher quality MPEG video.
Video Front end such as the Philips SA7110 can be built
in for Video Capture and live TV window.
The Media Port can accept pixel data streams from ei-
ther the pixel port or the PCI bus interface. The pixel data
stream pass through a FIFO before it gets written into
the frame buffer. A flexible decimation unit can be used
to reduce the input video frame size – usually required
for capturing camera input.
The video window for Media Port video stream is also
double buffered for anti-tearing. Interlaced video input can
be captured in two ways: one field only, or converted to
non-interlaced frame.
The Video Processor fully support Windows 95 Direct
Draw with features such as Chroma Key, Page flipping
and Blending.
VMI connector
To support a wide variety of Video and MPEG decoders,
the Media Port supports the VMI ( Video Module Inter-
P/N:PM0476
REV. 1.2 , FEB 11, 1998
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