adv7321 Analog Devices, Inc., adv7321 Datasheet - Page 54

• Manufacturer Part Number: adv7321
• Description: Multiformat 216 Mhz Video Encoder With Six Nsv 12-bit Dacs
• Manufacturer: Analog Devices, Inc.

ADV7320/ADV7321
For the length of 16 to 240, the gamma correction curve has to
be calculated as follows:
where:
y = gamma corrected output
x = linear input signal
γ = gamma power factor
To program the gamma correction registers, calculate the seven
values for y using the following formula:
where:
x
n = 24, 32, 48, 64, 80, 96, 128, 160, 192, or 224
y
gamma correction register
For example,
where the sum of each equation is rounded to the nearest
integer.
The gamma curves in Figure 71 and Figure 72 are examples only;
any user-defined curve is acceptable in the range of 16 to 240.
n
(n − 16)
= value for y along the y axis, which must be written into the
y = x γ
y
y
y
y
y
y
y
y
y
y
y
24
32
48
64
80
96
128
160
192
224
= Value for x along x axis at points
n
= [(8/224)0.5 × 224] + 16 = 58
= [(16/224)0.5 × 224] + 16 = 76
= [(32/224)0.5 × 224] + 16 = 101
= [(48/224)0.5 × 224] + 16 = 120
= [(64/224)0.5 × 224] + 16 = 136
= [(80/224)0.5 × 224] + 16 = 150
= [(112/224)0.5 × 224] + 16 = 174
= [(144/224)0.5 × 224] + 16 = 195
= [(176/224)0.5 × 224] + 16 = 214
= [(208/224)0.5 × 224] + 16 = 232
ª
«
¬
(
240
x
(
n


16
16
)
)
º
»
¼
J
u
(
240

16
)

16
Rev. 0 | Page 54 of 88
Figure 71. Signal Input (Ramp) and Signal Output for Gamma 0.5
300
250
200
150
100
300
250
200
150
100
Figure 72. Signal Input (Ramp) and Selectable Output Curves
50
50
0
0
0
0
GAMMA CORRECTION BLOCK OUTPUT TO A RAMP INPUT
GAMMA CORRECTION BLOCK TO A RAMP INPUT FOR
50
50
SIGNAL INPUT
VARIOUS GAMMA VALUES
100
100
LOCATION
LOCATION
0.5
1.5
1.8
0.3
0.5
SIGNAL OUTPUT
150
150
200
200
250
250