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ADV7180

Data Sheet

Rev. G | Page 40 of 120

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.

LUMA

OUTPUT

DNR1

LUMA PEAKING

FILTER

DNR2

LUMA

SIGNAL

Figure 30. DNR and Peaking Block Diagram

DNR_EN, Digital Noise Reduction Enable, Address 0x4D[5]

The DNR_EN bit enables the DNR block or bypasses it.

Table 49. DNR_EN Function

Setting

Description

Bypasses DNR (disable)

1 (default)

Enables digital noise reduction on the luma data

DNR_TH[7:0], DNR Noise Threshold, Address 0x50[7:0]

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

Description

0x08 (default)

Threshold for maximum luma edges to be

interpreted as noise

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

Description

0x40 (Default)

0 dB response

–20

FREQUENCY (MHz)

–5

–10

–15

PEAKING GAIN USING BP FILTER

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

Description

0x04 (default)

Threshold for maximum luma edges to be

interpreted as noise

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