adv7310 Analog Devices, Inc., adv7310 Datasheet - Page 52

• Manufacturer Part Number: adv7310
• Description: Multiformat 216 Mhz Video Encoder With Six Nsv 12-bit Dacs
• Manufacturer: Analog Devices, Inc.

ADV7310/ADV7311
SD Digital Noise Reduction
[Subaddress 63h, 64h, 65h]
DNR is applied to the Y data only. A filter block selects the high
frequency, low amplitude components 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 will be subtracted from the original signal. In DNR sharp-
ness mode, if the absolute value of the filter output is less than
the programmed threshold, it is assumed to be noise, as before.
Otherwise, if the level exceeds the threshold, now being identi-
fied as a valid signal, a fraction of the signal [coring gain border,
coring gain data] will be added to the original signal in order 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 [bor-
der 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.
–52–
Y DATA
Y DATA
INPUT
INPUT
DNR MODE
DNR
SHARPNESS
MODE
NOISE
SIGNAL PATH
NOISE
SIGNAL PATH
INPUT FILTER
INPUT FILTER
MAIN SIGNAL PATH
MAIN SIGNAL PATH
Figure 48. DNR Block Diagram
BLOCK
BLOCK
< THRESHOLD?
> THRESHOLD?
CORING GAIN BORDER
CORING GAIN BORDER
BLOCK SIZE CONTROL
OUTPUT
OUTPUT
BLOCK SIZE CONTROL
FILTER
FILTER
CORING GAIN DATA
CORING GAIN DATA
BLOCK OFFSET
BLOCK OFFSET
DNR CONTROL
BORDER AREA
DNR CONTROL
BORDER AREA
FILTER OUTPUT
FILTER OUTPUT
> THRESHOLD
< THRESHOLD
GAIN
GAIN
+
+
+
–
SUBTRACT SIGNAL
IN THRESHOLD
RANGE FROM
ORIGINAL SIGNAL
ADD SIGNAL
ABOVE THRESHOLD
RANGE FROM
ORIGINAL SIGNAL
DNR OUT
DNR OUT
REV. A