ADV7340 Datasheet, PDF (61/88 Pages) Analog Devices – Multiformat Video Encoder, Six 12-Bit Noise Shaped Video® DACS

When changing the adaptive filter mode to Mode B
(Subaddress 0x35, Bit 6), the output shown in Figure 76
can be obtained.
Figure 76. Output Signal from ED/HD Adaptive Filter (Mode B)
SD DIGITAL NOISE REDUCTION
Subaddress 0xA3 to Subaddress 0xA5
Digital noise reduction (DNR) is applied to the Y data only.
A filter block selects the high frequency, low amplitude compo-
nents of the incoming signal (DNR input select). The absolute
value of the filter output is compared to a programmable
threshold value (DNR threshold control). There are two DNR
modes available: DNR mode and DNR sharpness mode.
In DNR mode, if the absolute value of the filter output is smaller
than the threshold, it is assumed to be noise. A programmable
amount (coring gain border, coring gain data) of this noise
signal is subtracted from the original signal. In DNR sharpness
mode, if the absolute value of the filter output is less than the
programmed threshold, it is assumed to be noise. Otherwise, if
the level exceeds the threshold, now identified as a valid signal,
a fraction of the signal (coring gain border, coring gain data) is
added to the original signal to boost high frequency components
and sharpen the video image.
In MPEG systems, it is common to process the video information
in blocks of 8 pixels × 8 pixels for MPEG2 systems, or 16 pixels ×
16 pixels for MPEG1 systems (block size control). DNR can be
applied to the resulting block transition areas that are known to
contain noise. Generally, the block transition area contains two
pixels. It is possible to define this area to contain four pixels
(border area).
It is also possible to compensate for variable block positioning
or differences in YCrCb pixel timing with the use of the DNR
block offset.
The digital noise reduction registers are three 8-bit registers.
They are used to control the DNR processing.
ADV7340/ADV7341
Y DATA
INPUT
DNR MODE
DNR CONTROL
BLOCK SIZE CONTROL
BORDER AREA
BLOCK OFFSET
GAIN
CORING GAIN DATA
NOISE
CORING GAIN BORDER
SIGNAL PATH
INPUT FILTER
BLOCK
FILTER
OUTPUT
< THRESHOLD?
FILTER OUTPUT
> THRESHOLD
MAIN SIGNAL PATH
SUBTRACT
SIGNAL IN
THRESHOLD
RANGE FROM
ORIGINAL SIGNAL
–
+
DNR OUT
DNR
SHARPNESS
MODE
DNR CONTROL
BLOCK SIZE CONTROL
BORDER AREA
BLOCK OFFSET
GAIN
CORING GAIN DATA
NOISE
CORING GAIN BORDER
SIGNAL PATH
INPUT FILTER
BLOCK
Y DATA
INPUT
FILTER
OUTPUT
> THRESHOLD?
FILTER OUTPUT
< THRESHOLD
MAIN SIGNAL PATH
ADD SIGNAL
ABOVE
THRESHOLD
RANGE FROM
ORIGINAL SIGNAL
+
+
DNR OUT
Figure 77. SD DNR Block Diagram
Coring Gain Border—Subaddress 0xA3, Bits[3:0]
These four bits are assigned to the gain factor applied to border
areas. In DNR mode, the range of gain values is 0 to 1 in
increments of 1/8. 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 1/16. 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—Subaddress 0xA3, 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 to 1 in increments of 1/8. 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 1/16. This factor is applied to the DNR filter
output that lies above the threshold range. The result is added to
the original signal.
Rev. 0 | Page 61 of 88