ADV7181 AD [Analog Devices], ADV7181 Datasheet - Page 28

• Manufacturer Part Number: ADV7181
• Description: Multiformat SDTV Video Decoder
• Manufacturer: AD [Analog Devices]

ADV7181B
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.
Figure 12.Y S-VHS 18 Extra Wideband Filter (CCIR 601 Compliant)
Figure 13.Y S-VHS 18 Extra Wideband Filter (CCIR 601 Compliant)
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v740a COMBINED Y ANTIALIAS, CCIR MODE SHAPING FILTER,
v740a COMBINED Y ANTIALIAS, S-VHS LOW-PASS FILTERS,
Figure 11. Y S-VHS Combined Responses
v740a COMBINED Y ANTIALIAS, PAL NOTCH FILTERS,
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FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
Y RESAMPLE
Y RESAMPLE
Y RESAMPLE
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Rev. 0 | Page 28 of 96
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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The plots in Figure 15 show the overall response of all filters
together.
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.
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 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.
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Figure 14. Y S-VHS 18 Extra Wideband Filter (601)
v740a COMBINED Y ANTIALIAS, NTSC NOTCH FILTERS,
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FREQUENCY (MHz)
Y RESAMPLE
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