ADV7180
DIGITAL NOISE REDUCTION (DNR) AND LUMA
PEAKING FILTER
Digital noise reduction is based on the assumption that high
frequency signals with low amplitude are probably noise and
that their removal, therefore, improves picture quality. The
following are the two DNR blocks in the ADV7180: the DNR1
block before the luma peaking filter and the DNR2 block after
the luma peaking filter, as shown in Figure 30.
Data Sheet
PEAKING_GAIN[7:0], Luma Peaking Gain,
Address 0xFB[7:0]
This filter can be manually enabled. The user can select to boost
or to attenuate the mid region of the Y spectrum around 3 MHz.
The peaking filter can visually improve the picture by showing
more definition on the picture details that contain frequency
components around 3 MHz. The default value on this register
passes through the luma data unaltered. A lower value attenuates
the signal, and a higher value gains the luma signal. A plot of
the filter’s responses is shown in Figure 31.
Table 51. PEAKING_GAIN[7:0] Function
Setting
0x40 (Default)
15
LUMA
SIGNAL
DNR1
LUMA PEAKING
FILTER
DNR2
LUMA
OUTPUT
05700-051
Description
0 dB response
PEAKING GAIN USING BP FILTER
Figure 30. DNR and Peaking Block Diagram
DNR_EN, Digital Noise Reduction Enable, Address 0x4D[5]
FILTER RESPONSE (dB)
10
The DNR_EN bit enables the DNR block or bypasses it.
Table 49. DNR_EN Function
Setting
0
1 (default)
Description
Bypasses DNR (disable)
Enables digital noise reduction on the luma data
5
0
–5
–10
The DNR1 block is positioned before the luma peaking block.
The DNR_TH[7:0] value is an unsigned, 8-bit number used to
determine the maximum edge that is interpreted as noise and,
therefore, blanked from the luma data. Programming a large
value into DNR_TH[7:0] causes the DNR block to interpret
even large transients as noise and remove them. As a result, the
effect on the video data is more visible. Programming a small
value causes only small transients to be seen as noise and to be
removed.
Table 50. DNR_TH[7:0] Function
Setting
0x08 (default)
Description
Threshold for maximum luma edges to be
interpreted as noise
–20
0
1
2
3
4
FREQUENCY (MHz)
5
6
7
Figure 31. Peaking Filter Responses
DNR_TH2[7:0], DNR Noise Threshold 2,
Address 0xFC[7:0]
The DNR2 block is positioned after the luma peaking block
and, therefore, affects the gained luma signal. It operates in the
same way as the DNR1 block, but there is an independent
threshold control, DNR_TH2[7:0], for this block. This value is
an unsigned, 8-bit number used to determine the maximum
edge that is interpreted as noise and, therefore, blanked from
the luma data. Programming a large value into DNR_TH2[7:0]
causes the DNR block to interpret even large transients as noise
and remove them. As a result, the effect on the video data is more
visible. Programming a small value causes only small transients
to be seen as noise and to be removed.
Table 52. DNR_TH2[7:0] Function
Setting
0x04 (default)
Description
Threshold for maximum luma edges to be
interpreted as noise
Rev. G | Page 40 of 120
05700-052
DNR_TH[7:0], DNR Noise Threshold, Address 0x50[7:0]
–15
AD [ ANALOG DEVICES ]
