ADV7182 datasheet(39/96 Pages) AD

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Data Sheet

ADV7182

IF FILTER COMPENSATION

IFFILTSEL[2:0], IF Filter Select, Address 0xF8[2:0]

The IFFILTSEL[2:0] register allows the user to compensate for

SAW filter characteristics on a composite input, as would be

observed on tuner outputs. Figure 29 and Figure 30 show IF

filter compensation for NTSC and PAL, respectively.

The options for this feature are as follows:

•

Bypass mode

•

NTSC, consisting of three filter characteristics

•

PAL, consisting of three filter characteristics

See Table 95 for programming details.

Figure 29. NTSC IF Filter Compensation

Figure 30. PAL IF Filter Compensation

ADAPTIVE CONTRAST ENHANCEMENT (ACE)

ACE allows for the contrast of an image to be increased, depending

on the content of the picture. Normally, this allows bright areas

to be made brighter and dark areas to be made darker. However,

the ADV7182 ACE feature also allows for the contrast within

dark areas to be increased without significantly affecting bright

areas. This is particularly useful in automotive applications where it

can be important to be able to discern objects in shaded areas.

The ACE feature works by sampling the chroma and luma levels

in the inputted image. This information is then histogrammed,

and the resulting correction is applied to the entire image. This

correction is done in a nonlinear fashion so that more correction

can be applied to dark areas if required.

For normal use, the luma and chroma gain controls can be

used; however, in automotive applications, where dark areas

may need to be further enhanced, also use the gamma gain

controls.

The reaction time of the ACE function can be set using the

ACE_RESPONSE_SPEED[7:4] bits (see Table 96). The corrected

image is faded over the original image using alpha blending,

giving a gradual change in contrast with scene changes. The ACE_

RESPONSE_SPEED[7:4] bits determine the duration of the

transition from the original to the corrected image. A larger value

for these bits results in a faster transition time; however, a smaller

value gives more stability to rapid scene changes.

The ACE_CHROMA_MAX[7:4] bits are used to set a

maximum value that clips the chroma gain regardless of

the ACE_CHROMA_GAIN[3:0] settings.

The ACE_GAMMA_GAIN[3:0] bits are particularly useful in

automotive applications because they allow dramatic image

enhancement in dark regions by stretching the contrast of pixels

at the low (dark) values of the image histogram. The luma and

chroma gain controls are normally used; however, the

ACE_GAMMA_GAIN[3:0] bits should be used when further

stretching of the contrast in the dark areas of an image is needed.

ACE_ENABLE, User Sub Map 2, Address 0x80[7]

Enables ACE.

Table 62. ACE_ENABLE Function

ACE_ENABLE

Description

0 (default)

Disable ACE

Enable ACE

–12

2.0

5.0

FREQUENCY (MHz)

IF COMP FILTERS NTSC ZOOMED AROUND FSC

–2

–4

–6

–8

–10

2.5

3.0

3.5

4.0

4.5

–8

3.0

6.0

FREQUENCY (MHz)

IF COMP FILTERS PAL ZOOMED AROUND

fSC

–2

–4

–6

3.5

4.0

4.5

5.0

5.5

| Page 39 of 96

Rev. C

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