ADV7341_15 datasheet(67/108 Pages) AD

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Data Sheet

ADV7340/ADV7341

Rev. C | Page 67 of 108

to the DNR filter output that lies below the set threshold range.

The result is then subtracted from the original signal.

In DNR sharpness mode, the range of gain values is 0 to 0.5 in

increments of 1/16. This factor is applied to the DNR filter

output that lies above the threshold range. The result is added to

the original signal.

Figure 75. SD DNR Offset Control

DNR Threshold—Subaddress 0xA4, Bits[5:0]

These six bits are used to define the threshold value in the range

of 0 to 63. The range is an absolute value.

Border Area—Subaddress 0xA4, Bit 6

When this bit is set to Logic 1, the block transition area can be

defined to consist of four pixels. If this bit is set to Logic 0, the

border transition area consists of two pixels, where one pixel

refers to two clock cycles at 27 MHz.

Figure 76. SD DNR Border Area

Block Size Control—Subaddress 0xA4, Bit 7

This bit is used to select the size of the data blocks to be processed.

Setting the block size control function to Logic 1 defines a 16 pixel

× 16 pixel data block, and Logic 0 defines an 8 pixel × 8 pixel

data block, where one pixel refers to two clock cycles at 27 MHz.

DNR Input Select Control—Subaddress 0xA5, Bits[2:0]

Three bits are assigned to select the filter, which is applied to the

incoming Y data. The signal that lies in the pass band of the

selected filter is the signal that is DNR processed. Figure 77

shows the filter responses selectable with this control.

Figure 77. SD DNR Input Select

DNR Mode Control—Subaddress 0xA5, Bit 3

This bit controls the DNR mode selected. Logic 0 selects DNR

mode; Logic 1 selects DNR sharpness mode.

DNR works on the principle of defining low amplitude, high

frequency signals as probable noise and subtracting this noise

from the original signal.

In DNR mode, it is possible to subtract a fraction of the signal

that lies below the set threshold, assumed to be noise, from the

original signal. The threshold is set in DNR Register 1.

When DNR sharpness mode is enabled, it is possible to add a

fraction of the signal that lies above the set threshold to the

original signal because this data is assumed to be valid data and

not noise. The overall effect is that the signal is boosted (similar

to using the extended SSAF filter).

DNR Block Offset Control—Subaddress 0xA5, Bits[7:4]

Four bits are assigned to this control, which allows a shift of the

data block of 15 pixels maximum. Consider the coring gain

positions fixed. The block offset shifts the data in steps of one

pixel such that the border coring gain factors can be applied at the

same position regardless of variations in input timing of the data.

SD ACTIVE VIDEO EDGE CONTROL

Subaddress 0x82, Bit 7

The ADV7340/ADV7341 are able to control fast rising and

falling signals at the start and end of active video in order to

minimize ringing.

When the active video edge control feature is enabled

(Subaddress 0x82, Bit 7 = 1), the first three pixels and the last

three pixels of the active video on the luma channel are scaled

so that maximum transitions on these pixels are not possible.

At the start of active video, the first three pixels are multiplied

by 1/8, 1/2, and 7/8, respectively. Approaching the end of active

video, the last three pixels are multiplied by 7/8, 1/2, and 1/8,

respectively. All other active video pixels pass through

unprocessed.

O XXXXXXO O XXXXXXO

DNR27 TO DNR24 = 0x01

OFFSET CAUSED

BY VARIATIONS IN

INPUT TIMING

APPLY BORDER

CORING GAIN

APPLY DATA

CORING GAIN

720 × 485 PIXELS

(NTSC)

8 × 8 PIXEL BLOCK

TWO-PIXEL

BORDER

DATA

8 × 8 PIXEL BLOCK

FILTER C

FILTER B

FILTER A

FILTER D

FREQUENCY (MHz)

0.2

0.4

0.6

0.8

1.0

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