Samsung S5PC100, User Manual

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S5PC100 USER’S MANUAL (REV1.0) TVOUT & VIDEO DAC
9.7-17
3.6
ILLEGAL COLOR COMPENSATION (CVBS MODULE)
The CVBS sub-module also supports color compensation for illegal RGB data. Video data are usually processed
in the YCbCr coordinates. At the result of processing such as filtering and scaling, the values of YCbCr can
exceed their nominal range and becomes to have ill-defined values when they are transformed into RGB
coordinates. This causes unwanted artifacts at display. The Figure 9.7.15 illustrates the relation between YCbCr
coordinates and RGB coordinates:
Y = 255,
CB = CR = 128
255
0 255
Y
CB
W
Y
G
C
R M
B
BK
25
5
CR
All Possible
YCBCR Value
YCBCR Valid
Color Block
R = Red
G = Green
B = Blue
Y = Yellow
C = Cyan
M = Magenta
W = White
BK = Black
Figure 9.7-15 Color Cube Comparison
If YCbCr data outside of the RGB cube occurs, the CVBS sub-module compensates the value so that the result
falls within the RGB cube. A constant luma and constant hue approach is used for this compensation. The
luminance Y is not altered while the chrominance Cb and Cr are limited to the maximum valid values having the
same hue as the invalid color prior to limiting. The SDO_RGB_CC register controls the size of RGB cube that
determine color compensation range. Meanwhile, if illegal YCbCr data are transformed to CVBS or S-Video, there
might be an overflow which exceeds DAC conversion range. The CVBS sub-module also compensates this error.
The SDO_CVBS_CC_Y1, SDO_CVBS_CC_Y2, and SDO_CVBS_CC_C registers are used for the color
compensation for CVBS output and the SDO_YC_CC_Y1, SDO_YC_CC_Y2, and SDO_YC_CC_C registers are
used for the compensation for S-video output, respectively.