Sd Digital Noise Reduction; Figure 121: Sd Dnr Block Diagram - Analog Devices ADV8003 Hardware Manual

8.4.19. SD Digital Noise Reduction

The ADV8003 encoder block offers a feature for digital noise reduction (DNR). 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). Two DNR modes are available: DNR mode and DNR sharpness mode. Refer
to Figure 121.
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.
To enable the SD DNR feature,
dnr_en, Encoder Map, Address 0xE481[7]
This bit is used to enable the SD Digital Noise Reduction (DNR) function.
Rev. B, August 2013
DNR MODE
NOISE
SIGNAL PATH
INPUT FILTER
BLOCK
Y DATA
< THRESHOLD?
INPUT
MAIN SIGNAL PATH
DNR
SHARPNESS
MODE
NOISE
SIGNAL PATH
INPUT FILTER
BLOCK
Y DATA
> THRESHOLD?
INPUT
MAIN SIGNAL PATH

Figure 121: SD DNR Block Diagram

dnr_en must be programmed.
DNR CONTROL
BLOCK SIZE CONTROL
BORDER AREA
BLOCK OFFSET
GAIN
CORING GAIN DATA
CORING GAIN BORDER
FILTER
SUBTRACT
OUTPUT
SIGNAL IN
THRESHOLD
RANGE FROM
ORIGINAL SIGNAL
–
FILTER OUTPUT
> THRESHOLD +
DNR CONTROL
BLOCK SIZE CONTROL
BORDER AREA
BLOCK OFFSET
GAIN
CORING GAIN DATA
CORING GAIN BORDER
FILTER ADD SIGNAL
OUTPUT ABOVE
THRESHOLD
RANGE FROM
ORIGINAL SIGNAL
+
FILTER OUTPUT
< THRESHOLD
+
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ADV8003 Hardware Manual
DNR OUT
DNR OUT