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AMD Geode™ LX Processors Data Book 393
Video Processor
33234H
6.7.3 X and Y Upscaler
After the video data has been buffered, the upscaling algo-
rithm is applied. The Video Processor module employs a
Digital Differential Analyzer-style (DDA) algorithm for both
horizontal and vertical upscaling. The scaling parameters
are programmed via the Video Scale register (VP Memory
Offset 020h). The scalers support up to 8x scale factors
both horizontally and vertically. The scaled video pixel
stream is then passed through bi-linear interpolating filters
(2-tap, 8-phase) to smooth the output video, significantly
enhancing the quality of the displayed image.
The X and Y Upscaler uses the DDA and linear interpolat-
ing filter to calculate (via interpolation) the values of the pix-
els to be generated. The interpolation formula uses A
i,j
,
A
i,j+1
, A
i+1,j
, and A
i+1,j+1
values to calculate the value of
intermediate points. The actual location of calculated
points is determined by the DDA algorithm.
The location of each intermediate point is one of eight
phases between the original pixels (see Figure 6-26).
6.7.4 Color Space Converter
After scaling and filtering have been performed, YUV video
data is passed through the color space converter to obtain
24-bit RGB video data.
Color space conversion equations are based on the
BT.601-1 recommendation:
Standard definition color space conversion equations are
based on Microsoft’s recommendations as follows:
R = 1.164383(Y-16) + 1.596027(V-128)
G = 1.164383(Y-16) - 0.812968(V-128) - 0.391762
(U-128)
B = 1.164383(Y-16) + 2.017232(U-128)
For high definition video, the color space conversion equa-
tions are based on Rec. ITU-R BT.709 as follows:
R = 1.164383(Y-16) + 1.792742(V-128)
G = 1.164383(Y-16) - 0.532909(V-128) - 0.213249
(U-128)
B = 1.164383(Y-16) + 2.112402(U-128)
The color space converter clamps inputs to prevent them
from exceeding acceptable limits.
The color space converter can be bypassed for overlaying
16-bpp graphics data.
Figure 6-26. Linear Interpolation Calculation
b
1
b
2
x
z
y
A
i,j+1
A
i+1,j+1
A
i+1,j
A
i,j
Notes:
x and y are 0 - 7
b
1
A
ij,
()
8 y–
8
------------ A
i 1 j,+
()
y
8
---+=
b
2
A
ij,1+
()
8 y–
8
------------ A
i 1 j 1+,+
()
y
8
---+=
zb
1
()
8 x–
8
------------ b
2
()
x
8
---+=