ADV7194KST Analog Devices Inc, ADV7194KST Datasheet - Page 43

• Manufacturer Part Number: ADV7194KST
• Description: IC ENCODER VIDEO EXT-10 80-LQFP
• Manufacturer: Analog Devices Inc
• Type: Video Encoderr

Specifications of ADV7194KST

• Rohs Status: RoHS non-compliant
• Applications: DVD, PC Video, Multimedia
• Voltage - Supply, Analog: 3.3 V ~ 5 V
• Voltage - Supply, Digital: 3.3 V ~ 5 V
• Mounting Type: Surface Mount
• Package / Case: 80-LQFP
• Number Of Dac's: 6
• Adc/dac Resolution: 10b
• Screening Level: Commercial
• Package Type: LQFP
• Pin Count: 80
• For Use With: EVAL-ADV7194EB - BOARD EVAL FOR ADV7194
• Lead Free Status / RoHS Status: Not Compliant

GAMMA CORRECTION REGISTERS 0–13 (GAMMA
CORRECTION 0–13)
(Address (SR5–SR0) = 26H–32H)
The Gamma Correction Registers are fourteen 8-bit-wide regis-
ters. They are used to program the gamma correction Curves A
and B.
Generally 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 wher-
ever nonlinear 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.
Location 0, 16, 240 and 255 are fixed and can not 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
γ = 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
Example:
(n-16)
n
= Value for x along x-axis at points n = 32, 64, 96, 128,
= Value for y along the y-axis, which has to be written
160, 192 or 224
into the gamma correction register
y
n
= [x
(n–16)
γ = gamma power factor
Signal
/(240–16)]
OUT
DNR27
y = x
DNR DNR DNR DNR
27
0
0
0
•
•
•
1
1
1
= (Signal
26
γ
γ
BLOCK OFFSET CONTROL
0
0
0
•
•
•
1
1
1
× (240–16) + 16
DNR26
25
0
0
1
•
•
•
0
1
1
IN
24
)
0
1
0
•
•
•
1
0
1
γ
0 PIXEL OFFSET
1 PIXEL OFFSET
2 PIXEL OFFSET
13 PIXEL OFFSET
14 PIXEL OFFSET
15 PIXEL OFFSET
DNR25
•
•
•
DNR24
DNR23
0
1
DNR MODE
CONTROL
DNR23
DNR MODE
DNR
SHARPNESS
MODE
y
y
y
y
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.
Rounded to the nearest integer.
32
64
96
128
= [(16/224)
= [(48/224)
= [(80/224)
= [(112/224)
300
250
200
150
100
300
250
200
150
100
DNR22
50
50
0
0
0
0
300
250
200
150
100
50
DNR DNR DNR
22
0
0
0
1
GAMMA CORRECTION BLOCK OUTPUT
TO A RAMP INPUT
GAMMA CORRECTION BLOCK OUTPUT
TO A RAMP INPUT FOR VARIOUS GAMMA VALUES
DNR INPUT SELECT CONTROL
21
0.5
0.5
0.5
0
1
1
0
0.5
DNR21
× 224] + 16
× 224] + 16 =120
× 224] + 16 = 150
50
50
20
× 224] + 16 = 174
1
0
1
0
FILTER A
FILTER B
FILTER C
FILTER D
SIGNAL INPUT
0.3
100
100
DNR20
1.5
0.5
0.5
SIGNAL OUTPUTS
LOCATION
LOCATION
SIGNAL OUTPUT
=
76
1.8
150
150
200
200
ADV7194
250
250