AMD Geode™ SC2200 Processor Data Book 331
Video Processor Module 32580B
7.2.3.1 YUV to RGB CSC in Video Data Path
This CSC must be enabled if the video data is in the YUV
color space. The CSC_FOR_VIDEO bit, F4BAR0+Memory
Offset 4Ch[10], controls this CSC.
YUV video data is passed through this CSC to obtain 24-bit
RGB data using the following CCIR-601-1 recommended
formula:
•R = 1.1640625(Y – 16) + 1.59375(V – 128)
•G = 1.1640625(Y – 16) – 0.8125(V – 128) –
0.390625(U – 128)
•B = 1.1640625(Y – 16) + 2.015625(U – 128)
The CSC clamps inputs to prevent them from exceeding
acceptable limits.
7.2.3.2 Gamma Correction
Either the video or graphics data can be routed through an
integrated palette RAM for Gamma correction. There are
three 256-byte RAMs, one for each color component value.
Gamma correction supported in the YUV or RGB color
space for the video data and RGB color space for the
graphics data. Gamma correction is accomplished by treat-
ing each color component as an address into each RAM.
The output of the RAM is the new color. A simple RGB
Gamma correction example is to increase each color com-
ponent by one. The address 00h in the RAMs would con-
tain the data 01h. The address 01h would contain the data
02h and so on. This would have the effect of increasing
each original Red, Green, and Blue value by one.
•G_V_GAMMA, F4BAR0+Memory Offset 04h[21] selects
which data path (video or graphics) to send to the
Gamma correction block. GAMMA_EN,
F4BAR0+Memory Offset 28h[0] enables the Gamma
correction function. To load the Gamma correction
palette RAM, use F4BAR0+Memory Offset 1Ch and
20h.
7.2.3.3 Color/Chroma Key
A color/chroma key mechanism is used to support the
Mixer/Blender logic. There are two keys: key1 is for the
cursor and key2 is for graphics or video data. Key1, the
cursor key, is always a color key. The cursor color key reg-
isters are located at, F4BAR0+Memory Offset 50h-5CF.
How the cursor key mechanism works with the Mixer/
Blender is explained in Section 7.2.3.4.
COLOR_CHROMA_KEY (F4BAR0+Memory Offset
04h[20]) determines whether key2 is a color key or a
chroma key. The Video Color Key Register
(F4BAR0+Memory Offset 14h) stores the key. Color keying
is used when video is overlaid on the graphics
(GFX_INS_VIDEO, F4BAR0+Memory Offset 4Ch[8] = 0).
Chroma keying is used when graphics is overlaid on the
video (GFX_INS_VIDEO = 1). How the color/chroma key
mechanism works with the Mixer/Blender is explained in
Section 7.2.3.4.
Table 7-1. Valid Mixing/Blending Configurations
Mixing/Blending1
(Bit)
Flicker
Filter2 (Bit)
Mode Comment13 11 10 9 30 29
001000Input: YUV Progressive Video
Mixing: RGB
•Produces highest quality RGB output (see Section
7.2.1.2 "Capture Video Mode", Weave subsection on
page325).
100000Input: RGB Progressive Video
Mixing: RGB
•Produces highest quality RGB output (see Section
7.2.1.2 "Capture Video Mode", Weave subsection on
page325).
010101Input: YUV Interlaced Video
Mixing: YUV
•Not supported.
010000Input: YUV Progressive Video
Mixing: YUV
•Not supported.
001000Input: YUV Interlaced Video
upscaled by 2
Mixing: RGB
•Typically Direct Video mode.
•Must be vertically upscaled by a factor of 2 (see
Section 7.2.2.5 "2-Tap Vertical and Horizontal
Upscalers" on page 329).
1. F4BAR0+Memory Offset 4Ch[13, 11:9].
2. F4BAR0+Memory Offset 814h[30:29].