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參數資料
| 型號： | ADV7152 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | CMOS 220 MHz True-Color Graphics Triple 10-Bit Video RAM-DAC(三通道,10位視頻RAM-D/A轉換器) |
| 中文描述： | 220兆赫的CMOS真彩色圖形三路10位顯存，數模轉換器（三通道，10位視頻RAM的的D / A轉換器） |
| 文件頁數： | 19/32頁 |
| 文件大小： | 322K |
| 代理商： | ADV7152 |
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ADV7152
–26–
REV. B
APPENDIX 3
10-BIT DACS AND GAMMA CORRECTION
10-Bit DACs
10-bit RAM-DAC resolution allows for nonlinear video correc-
tion, in particular Gamma Correction. The ADV7152 allows for
an increase in color resolution from 24-bit to 30-bit effective
color without the necessity of a 30-bit deep frame buffer. In
true-color mode, for example, the part effectively operates as a
24-bit to 30-bit color look-up table.
Up to now we have assumed that there exists a linear relation-
ship between the actual RGB values input to a monitor and the
intensity produced on the screen. This, however, is not the case.
Half scale digital input (1000 0000) might correspond to only
20% output intensity on the CRT (Cathode Ray Tube). The in-
tensity (ICRT) produced on a CRT by an input value IIN is given
by:
ICRT = (IIN)χ
where
χ ranges from 2.0 to 2.8.
If the individual values of
χ for red, green and blue are known,
then so called “Gamma Correction” can be applied to each of
the three video input signals (IIN);
therefore:
IIN(corrected) = k(IIN)
1/
χ
(k = 1, normally)
Traditionally, there has been a tradeoff between implementing a
nonlinear graphics function, such as gamma correction, and
color dynamic range. The ADV7152 overcomes this by increas-
ing the individual color resolution of each of the red, green and
blue primary colors from 8 bits per color channel to 10 bits per
channel (24 bits to 30 bits).
The table highlights the loss of resolution when 8-bit data is
gamma-corrected to a value of 2.7 and quantized in a tradi-
tional 8-bit system. Note that there is no change in the 8-bit
quantized data for linear changes in the input data over much of
the transfer function. On the other hand, when quantized to 10
bits via the 10-bit RAMs and 10-bit DACs of the ADV7152, all
changes on the input 8-bit data are reflected in corresponding
changes in the 10-bit data.
The graph shows a typical gamma curve corresponding to a
gamma value of 2.7. This is programmed to the red, green and
blue RAMs of the color lookup table instead of the more tradi-
tional linear function. Different curves corresponding to any
particular gamma value can be independently programmed to
each of the red, green and blue RAMs.
Other applications of the 10-bit RAM-DAC include closed-loop
monitor color calibration.
Gamma Correction 8 Bits vs. 10 Bits
Gamma
Corrected
Quantized to
8-Bit Data
(2.7)
8 Bits
10 Bits
240
0.977797
250
1001
241
0.979304
250
1002
242
0.980807
251
1004
243
0.982306
251
1005
244
0.983801
25 1
1007
245
0.985292
252
1008
246
0.986780
252
1010
247
0.988264
252
1011
248
0.989744
253
1013
249
0.991220
253
1015
250
0.992693
254
1016
251
0.994161
254
1018
252
0.995626
254
1019
253
0.997088
255
1021
254
0.998546
255
1022
255
1.000000
255
1023
1.00
0.00
256
0.30
0.10
32
0.20
0
0.60
0.40
0.50
0.70
0.80
0.90
224
192
160
128
96
64
INPUT CODE – Decimal
DAC
OUTPUT
–
Normalized
to
1
GAMMA
CORRECTION
CURVE
LINEAR
RESPONSE
PRECEIVED
BY
THE
EYE
CRT
RESPONSE
Gamma Correction Curve (Gamma Value = 2.7)
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相關代理商/技術參數 |
參數描述 |
|---|---|
| adv7152es | 制造商:Rochester Electronics LLC 功能描述:- Bulk 制造商:Analog Devices 功能描述: |
| ADV7152KS110 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Video DAC with Color Palette (RAMDAC) |
| ADV7152KS135 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Video DAC with Color Palette (RAMDAC) |
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| ADV7152KS85 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Video DAC with Color Palette (RAMDAC) |
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