ADV7181BBCPZ datasheet(28/96 Pages) AD

28 / 96 page

ADV7181B

Rev. 0 | Page 28 of 96

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FREQUENCY (MHz)

v740a COMBINED Y ANTIALIAS, S-VHS LOW-PASS FILTERS,

Y RESAMPLE

Figure 11. Y S-VHS Combined Responses

The filter plots in Figure 11 show the S-VHS 1 (narrowest) to

S-VHS 18 (widest) shaping filter settings. Figure 13 shows the

PAL notch filter responses. The NTSC-compatible notches are

shown in Figure 14.

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v740a COMBINED Y ANTIALIAS, CCIR MODE SHAPING FILTER,

Y RESAMPLE

Figure 12.Y S-VHS 18 Extra Wideband Filter (CCIR 601 Compliant)

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v740a COMBINED Y ANTIALIAS, PAL NOTCH FILTERS,

Y RESAMPLE

Figure 13.Y S-VHS 18 Extra Wideband Filter (CCIR 601 Compliant)

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v740a COMBINED Y ANTIALIAS, NTSC NOTCH FILTERS,

Y RESAMPLE

Figure 14. Y S-VHS 18 Extra Wideband Filter (601)

CHROMA FILTER

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

of filters. Note that the data format at this point is CVBS for

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

YPrPb input formats.

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Chroma Antialias Filter (CAA). The ADV7181B over-

samples the CVBS by a factor of 2 and the Chroma/PrPb

by a factor of 4. A decimating filter (CAA) is used to

preserve the active video band and to remove any out-of-

band components. The CAA filter has a fixed response.

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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.

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Digital Resampling Filter. This block is used to allow

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.

The plots in Figure 15 show the overall response of all filters

together.

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