ADV7390/ADV7391/ADV7392/ADV7393
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 as
before. However, if the level exceeds the threshold, now being
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 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).
Figure 76. Input Signal to ED/HD Adaptive Filter
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.
DNR MODE
DNR CONTROL
BLOCK SIZE CONTROL
BORDER AREA
BLOCK OFFSET
Figure 77. Output Signal from ED/HD Adaptive Filter (Mode A)
GAIN
CORING GAIN DATA
When changing the adaptive filter mode to Mode B
(Subaddress 0x35, Bit 6), the output shown in Figure 78
can be obtained.
CORING GAIN BORDER
NOISE
SIGNAL PATH
INPUT FILTER
BLOCK
FILTER
SUBTRACT
OUTPUT
SIGNAL IN
Y DATA
INPUT
< THRESHOLD?
THRESHOLD
RANGE FROM
ORIGINAL SIGNAL
–
FILTER OUTPUT
> THRESHOLD
+
DNR OUT
MAIN SIGNAL PATH
DNR
SHARPNESS
MODE
DNR CONTROL
BLOCK SIZE CONTROL
BORDER AREA
BLOCK OFFSET
GAIN
CORING GAIN DATA
CORING GAIN BORDER
NOISE
SIGNAL PATH
Figure 78. Output Signal from ED/HD Adaptive Filter (Mode B)
INPUT FILTER
BLOCK
FILTER
ADD SIGNAL
ABOVE
THRESHOLD
RANGE FROM
ORIGINAL SIGNAL
SD DIGITAL NOISE REDUCTION
Subaddress 0xA3 to Subaddress 0xA5
OUTPUT
Y DATA
INPUT
> THRESHOLD?
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.
+
FILTER OUTPUT
< THRESHOLD
+
DNR OUT
MAIN SIGNAL PATH
Figure 79. SD DNR Block Diagram
Rev. 0 | Page 57 of 96
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