ADV7190KST Analog Devices Inc, ADV7190KST Datasheet - Page 42

• Manufacturer Part Number: ADV7190KST
• Manufacturer: Analog Devices Inc

Specifications of ADV7190KST

• Number Of Dac's: 6
• Adc/dac Resolution: 10b
• Screening Level: Commercial
• Package Type: LQFP
• Pin Count: 64
• Lead Free Status / RoHS Status: Not Compliant

ADV7190/ADV7191
GAMMA CORRECTION REGISTERS 0–13
(GAMMA CORRECTION 0–13)
(Address (SR5–SR0) = 26H–32H)
The Gamma Correction Registers are fourteen 8-bit-wide
registers. They are used to program the gamma correction
Curves A and B.
Gamma correction is applied to compensate for the nonlinear
relationship between signal input and brightness level output (as
perceived on the CRT). It can also be applied wherever nonlin-
ear processing is used.
Gamma correction uses the function:
where
Gamma correction is performed on the luma data only. The
user has the choice to use two different curves, Curve A, or
Curve B. At any one time only one of these curves can be used.
The response of the curve is programmed at seven predefined
locations. In changing the values at these locations the gamma
curve can be modified. Between these points linear interpolation
is used to generate intermediate values. Considering the curve
to have a total length of 256 points, the seven locations are at:
32, 64, 96, 128, 160, 192, and 224.
Values at Location 0, 16, 240, and 255 are fixed and cannot
be changed.
For the length of 16 to 240 the gamma correction curve has to
be calculated as below:
where
y = gamma corrected output
x = linear input signal
g = gamma power factor
To program the gamma correction registers, the seven values for
y have to be calculated using the following formula:
where
x
y
n
Example:
y
y
(n-16) =
n
32
64
= [(16/224)
= [(48/224)
=
= 32, 64, 96, 128, 160, 192, or 224
Value for x along x-axis
Value for y along the y-axis, which has to be written
into the gamma correction register
y
n
= [x(
0.5
0.5
¥ 224] + 16
¥ 224] + 16 =120*
n–16)
g = gamma power factor
Signal
/(240–16) ]
OUT
DNR27
y = x
DNR DNR DNR DNR
=
27
= (Signal
0
0
0
•
•
•
1
1
1
76*
g
26
g
0
0
0
•
•
•
1
1
1
¥ (240–16) + 16
DNR26
25
BLOCK OFFSET
0
0
1
•
•
•
0
1
1
IN )
24
0
1
0
•
•
•
1
0
1
g
0 PIXEL OFFSET
1 PIXEL OFFSET
2 PIXEL OFFSET
13 PIXEL OFFSET
14 PIXEL OFFSET
15 PIXEL OFFSET
DNR25
•
•
•
Figure 84. DNR Register 2
DNR24
DNR23
–42–
0
1
DNR MODE
CONTROL
DNR23
y
y
*Rounded to the nearest integer.
The above will result in a gamma curve shown below, assuming
a ramp signal as an input.
The gamma curves shown above are examples only, any user-
defined curve is acceptable in the range of 16–240.
DNR MODE
DNR
SHARPNESS
MODE
96
128
Figure 85. Signal Input (Ramp) and Signal Output for
Gamma 0.5
Figure 86. Signal Input (Ramp) and Selectable Gamma
Output Curves
= [(80/224)
= [(112/224)
300
250
200
150
100
300
250
200
150
100
50
50
DNR22
0
0
0
0
300
250
200
150
100
50
DNR DNR DNR
GAMMA CORRECTION BLOCK OUTPUT
TO A RAMP INPUT
GAMMA CORRECTION BLOCK OUTPUT
TO A RAMP INPUT FOR VARIOUS GAMMA VALUES
22
0
0
0
1
0.5
21
0
1
1
0
0.5
DNR INPUT SELECT
¥ 224] + 16 = 150*
DNR21
50
50
¥ 224] + 16 = 174*
20
1
0
1
0
SIGNAL INPUT
0.3
FILTER A
FILTER B
FILTER C
FILTER D
100
100
DNR20
1.5
0.5
0.5
SIGNAL OUTPUTS
SIGNAL OUTPUT
LOCATION
LOCATION
1.8
150
150
200
200
250
250
REV. B