ADV7180
•
•
Chroma Shaping Filters (CSH).
CHROMA FILTER
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.
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.
Digital Resampling Filter.
•
Chroma Antialias Filter (CAA).
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.
The ADV7180 oversamples the CVBS by a factor of 4 and
the chroma/YPrPb by a factor of 2. 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.
Figure 23 shows the overall response of all filters together.
COMBINED Y ANTIALIAS, NTSC NOTCH FILTERS,
Y RESAMPLE
COMBINED Y ANTIALIAS, CCIR MODE SHAPING FILTER,
Y RESAMPLE
0
–20
0
–10
–20
–30
–40
–50
–60
–70
–40
–60
–80
–100
–120
0
2
4
6
8
10
12
0
2
4
6
8
10
12
FREQUENCY (MHz)
FREQUENCY (MHz)
Figure 22. Y S-VHS 18 Extra Wideband Filter (CCIR 601 Compliant)
Figure 20. Y S-VHS 18 Extra Wideband Filter (CCIR 601 Compliant)
COMBINED C ANTIALIAS, C SHAPING FILTER,
C RESAMPLER
COMBINED Y ANTIALIAS, PAL NOTCH FILTERS,
Y RESAMPLE
0
–10
–20
–30
–40
–50
–60
0
–10
–20
–30
–40
–50
–60
–70
0
1
2
3
4
5
6
0
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10
12
FREQUENCY (MHz)
FREQUENCY (MHz)
Figure 23. Chroma Shaping Filter Responses
Figure 21. Y S-VHS 18 Extra Wideband Filter (CCIR 601 Compliant)
Rev. A | Page 31 of 112
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