ADV7180
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.
•
Chroma Antialias Filter (CAA).
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.
•
•
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.
COMBINED Y ANTIALIAS, CCIR MODE SHAPING FILTER,
Y RESAMPLE
0
COMBINED Y ANTIALIAS, NTSC NOTCH FILTERS,
Y RESAMPLE
0
–10
–20
–30
–40
–50
–20
AMPLITUDE (dB)
–40
–60
–80
–100
05700-020
AMPLITUDE (dB)
–120
0
2
4
6
8
10
12
–70
0
2
4
6
8
10
12
FREQUENCY (MHz)
FREQUENCY (MHz)
Figure 20. Y S-VHS 18 Extra Wideband Filter (CCIR 601 Compliant)
COMBINED Y ANTIALIAS, PAL NOTCH FILTERS,
Y RESAMPLE
0
–10
–20
–30
–40
–50
Figure 22. Y S-VHS 18 Extra Wideband Filter (CCIR 601 Compliant)
COMBINED C ANTIALIAS, C SHAPING FILTER,
C RESAMPLER
0
–10
ATTENUATION (dB)
AMPLITUDE (dB)
–20
–30
–40
05700-021
–70
–60
0
2
4
6
8
10
12
0
1
2
3
4
5
6
FREQUENCY (MHz)
FREQUENCY (MHz)
Figure 21. Y S-VHS 18 Extra Wideband Filter (CCIR 601 Compliant)
Figure 23. Chroma Shaping Filter Responses
Rev. A | Page 31 of 112
05700-023
–60
–50
05700-022
–60
AD [ ANALOG DEVICES ]
