ADV7182ABCPZ datasheet(32/102 Pages) AD

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ADV7182A

Data Sheet

Rev. 0 | Page 32 of 102

CHROMA FILTER

Data from the digital fine clamp block is processed by the three

sets of filters as follows (the data format at this point is CVBS for

CVBS inputs, chroma only for Y/C, or U/V interleaved for YPrPb

input formats):



Chroma antialias filter (CAA). The ADV7182A oversamples

the CVBS by a factor of 4. A decimating filter (CAA) preserves

the active video band and removes any out of band

components. The CAA filter has a fixed response.



Chroma shaping filters (CSH). The shaping filter block

(CSH) can be programmed to perform a variety of low-pass

responses. It can be used to selectively reduce the bandwidth

of the chroma signal for scaling or compression.



Digital resampling filter. This block allows dynamic

resampling of the video signal to alter parameters such as

the time base of a line of video. Fundamentally, the resampler

is a set of low-pass filters. The actual response is chosen by

the system without user intervention.

Figure 22 shows the overall response of all filters together.

Figure 19. Combined Y Antialias, CCIR Mode Shaping Filter

Figure 20. Combined Y Antialias, PAL Notch Filters

Figure 21. Combined Y Antialias Filter, NTSC Notch Filters

Figure 22. Chroma Shaping Filter Responses

CSFM[2:0], C Shaping Filter Mode—Address 0x17, Bits[7:5]

The C shaping filter mode bits allow the user to select from a

range of low-pass filters for the chrominance signal. When

switched in automatic mode, the widest filter is selected based

on the video standard/format and user choice (see the 000 and

001 settings in Table 39).

Table 39. CSFM Function

CSFM[2:0]

Description

000 (default)

Autoselection 1.5 MHz bandwidth

001

Autoselection 2.17 MHz bandwidth

010

SH1

011

SH2

100

SH3

101

SH4

110

SH5

111

Wideband mode

Figure 22 shows the responses of SH1 (narrowest) to SH5

(widest) in addition to the wideband mode (shown in red).

–20

–40

–60

–80

–100

–120

010

212

FREQUENCY (MHz)

COMBINED Y ANTIALIAS, CCIR MODE SHAPING FILTER,

Y RESAMPLE

–10

–20

–30

–40

–50

–60

–70

010

212

FREQUENCY (MHz)

COMBINED Y ANTIALIAS, PAL NOTCH FILTERS,

Y RESAMPLE

–10

–20

–30

–40

–50

–60

–70

010

212

FREQUENCY (MHz)

COMBINED Y ANTIALIAS, NTSC NOTCH FILTERS,

Y RESAMPLE

–10

–20

–30

–40

–50

–60

FREQUENCY (MHz)

COMBINED C ANTIALIAS, C SHAPING FILTER,

C RESAMPLER

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