ADV8005 Hardware Reference Manual
UG-707
Figure 126: Output Signal from ED/HD Adaptive Filter (Mode B)
7.4.19.
SD Digital Noise Reduction
The
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 127: SD DNR Block Diagram
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
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BLOCK SIZE CONTROL
BORDER AREA
BLOCK OFFSET
CORING GAIN DATA
CORING GAIN BORDER
GAIN
DNR CONTROL
FILTER
OUTPUT
> THRESHOLD?
INPUT FILTER
BLOCK
FILTER OUTPUT
< THRESHOLD
DNR OUT
+
+
MAIN SIGNAL PATH
ADD SIGNAL
ABOVE
THRESHOLD
RANGE FROM
ORIGINAL SIGNAL
DNR
SHARPNESS
MODE
NOISE
SIGNAL PATH
Y DATA
INPUT
BLOCK SIZE CONTROL
BORDER AREA
BLOCK OFFSET
CORING GAIN DATA
CORING GAIN BORDER
GAIN
DNR CONTROL
FILTER
OUTPUT
< THRESHOLD?
INPUT FILTER
BLOCK
FILTER OUTPUT
> THRESHOLD
DNR OUT
MAIN SIGNAL PATH
SUBTRACT
SIGNAL IN
THRESHOLD
RANGE FROM
ORIGINAL SIGNAL
DNR MODE
NOISE
SIGNAL PATH
Y DATA
INPUT
–
+
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