adv7322 Analog Devices, Inc., adv7322 Datasheet - Page 56

• Manufacturer Part Number: adv7322
• Description: Multiformat 11-bit Hdtv Video Encoder
• Manufacturer: Analog Devices, Inc.

ADV7322
HD SHARPNESS FILTER AND ADAPTIVE FILTER
CONTROLS
[Subaddresses 0x20, 0x38 to 0x3D]
There are three filter modes available on the ADV7322:
sharpness filter mode and two adaptive filter modes.
HD Sharpness Filter Mode
To enhance or attenuate the Y signal in the frequency ranges
shown in Figure 72, the following register settings must be used:
HD sharpness filter must be enabled and HD adaptive filter
enable must be set to disabled.
To select one of the 256 individual responses, the corresponding
gain values, which range from –8 to +7, for each filter must be
programmed into the HD sharpness filter gain register at
Address 0x20.
HD Adaptive Filter Mode
The HD adaptive filter threshold A, B, and C registers, the HD
adaptive filter gain 1, 2, and 3 registers, and the HD sharpness
gain register are used in adaptive filter mode. To activate the
adaptive filter control, the HD sharpness filter and the HD
adaptive filter must be enabled.
SIGNAL:
INPUT
STEP
^
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
FILTER A RESPONSE (Gain Ka)
FREQUENCY (MHz)
SHARPNESS AND ADAPTIVE FILTER CONTROL BLOCK
Figure 72. Sharpness and Adaptive Filter Control Block
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
Rev. PrA | Page 56 of 88
FILTER B RESPONSE (Gain Kb)
FREQUENCY (MHz)
The derivative of the incoming signal is compared to the three
programmable threshold values: HD adaptive filter threshold A,
B, and C. The recommended threshold range is from 16 to 235,
although any value in the range of 0 to 255 can be used.
The edges can then be attenuated with the settings in HD
adaptive filter gain 1, 2, and 3 registers and HD sharpness filter
gain register.
According to the settings of the HD adaptive filter mode
control, there are two adaptive filter modes available:
1.
2.
Mode A is used when adaptive filter mode is set to 0.
In this case, Filter B (LPF) will be used in the adaptive
filter block. Also, only the programmed values for
Gain B in the HD sharpness filter gain and HD
adaptive filter gain 1, 2, and 3 are applied when
needed. The Gain A values are fixed and cannot be
changed.
Mode B is used when adaptive filter mode is set to 1.
In this mode, a cascade of Filter A and Filter B is used.
Both settings for Gain A and Gain B in the HD
sharpness filter gain and HD adaptive filter gain 1, 2,
and 3 become active when needed.
1.6
1.5
1.4
1.3
1.2
1.1
1.0
Preliminary Technical Data
FREQUENCY RESPONSE IN SHARPNESS
0
FILTER MODE WITH Ka = 3 AND Kb = 7
2
FREQUENCY (MHz)
4
6
8
10
12