adv7305a Analog Devices, Inc., adv7305a Datasheet - Page 48

• Manufacturer Part Number: adv7305a
• Description: Multiformat Sd, Progressive Scan/hdtv Video Encoder With Six Nsv 14-bit Dacs
• Manufacturer: Analog Devices, Inc.

ADV7304A/ADV7305A
The Digital Noise Reduction Registers are three 8-bit wide
registers. They are used to control the DNR processing.
Coring Gain Border
[Address 63h, Bits 3–0]
These four bits are assigned to the gain factor applied to the
border areas. In DNR Mode, the range of gain values is 0–1, in
increments of 0.125. This factor is applied to the DNR filter
output that lies below the set threshold range. The result is then
subtracted from the original signal.
In DNR Sharpness Mode, the range of gain values is 0 to 0.5, in
increments of 0.0625. This factor is applied to the DNR filter
output that lies above the threshold range. The result is added
to the original signal.
Coring Gain Data
[Address 63h, Bits 7–4]
These four bits are assigned to the gain factor applied to the
luma data inside the MPEG pixel block.
In DNR Mode, the range of gain values is 0–1, in increments of
0.125. This factor is applied to the DNR filter output that lies
below the set threshold range. The result is then subtracted
from the original signal.
In DNR Sharpness Mode, the range of gain values is 0–0.5, in
increments of 0.0625. This factor is applied to the DNR filter
output that lies above the threshold range. The result is added
to the original signal.
DNR Threshold
[Address 64h, Bits 5–0]
These six bits are used to define the threshold value in the range
of 0 to 63. The range is an absolute value.
Border Area
[Address 64h, Bit 6]
In setting this bit to a Logic “1,” the block transition area can
be defined to consist of four pixels. If this bit is set to a Logic
“0,” the border transition area consists of two pixels, where one
pixel refers to two clock cycles at 27 MHz.
DNR27 – DNR24 = 01HEX
720 485 PIXELS
(NTSC)
Figure 69. DNR Block Offset Control
Figure 70. DNR Border Area
APPLY DATA
CORING GAIN
O X X X X X X O O X X X X X X O
O X X X X X X O O X X X X X X O
O X X X X X X O O X X X X X X O
8 8 PIXEL BLOCK
APPLY BORDER
CORING GAIN
BORDER DATA
2 PIXEL
8 8 PIXEL BLOCK
OFFSET CAUSED
BY VARIATIONS IN
INPUT TIMING
–48–
Block Size Control
[Address 64h, Bit 7]
This bit is used to select the size of the data blocks to be pro-
cessed. Setting the block size control function to a Logic “1”
defines a 16
pixel data block, where 1 pixel refers to 2 clock cycles at 27 MHz.
DNR Input Select Control
[Address 65h, Bits 2–0]
Three bits are assigned to select the filter that is applied to the
incoming Y data. The signal that lies in the pass band of the
selected filter is the signal that will be DNR processed. The figure
below shows the filter responses selectable with this control.
DNR Mode Control
[Address 65h, Bit 3]
This bit controls the DNR Mode selected. A Logic “0” selects
DNR Mode, and Logic “1” selects DNR Sharpness Mode.
DNR works on the principle of defining low amplitude, high
frequency signals as probable noise and subtracting this noise
from the original signal.
In DNR Mode, it is possible to subtract a fraction of the signal
that lies below the set threshold, assumed to be noise, from the
original signal. The threshold is set in DNR Register 1.
When DNR Sharpness Mode is enabled, it is possible to add a
fraction of the signal that lies above the set threshold to the origi-
nal signal, since this data is assumed to be valid data and not
noise. The overall effect is that the signal will be boosted (similar
to using extended SSAF filter).
Block Offset Control
[Address 65h, Bits 7–4]
Four bits are assigned to this control, which allows a shift of the
data block of 15 pixels maximum. Consider the coring gain posi-
tions fixed. The block offset shifts the data in steps of one pixel
such that the border coring gain factors can be applied at the
same position regardless of variations in input timing of the data.
1.0
0.8
0.6
0.4
0.2
0
0
FILTER C
FILTER D
16 pixel data block, a Logic “0” defines an 8
Figure 71. DNR Input Select
1
2
FREQUENCY – Hz
FILTER B
3
FILTER A
4
5
6
REV. A
8