ADV7180
CHROMA FILTER
Data from the digital fine clamp block is processed by the three
sets of filters that follow. 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.
COMBINED Y ANTIALIAS, CCIR MODE SHAPING FILTER,
Y RESAMPLE
0
0
–10
–20
–30
–40
–50
Data Sheet
•
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, NTSC NOTCH FILTERS,
Y RESAMPLE
–20
AMPLITUDE (dB)
–40
–60
–80
05700-020
–120
0
2
4
6
8
10
12
FREQUENCY (MHz)
–70
0
2
4
6
8
10
12
FREQUENCY (MHz)
Figure 23. Combined Y Antialias, CCIR Mode Shaping Filter
Figure 25. Combined Y Antialias Filter, NTSC Notch Filters
COMBINED C ANTIALIAS, C SHAPING FILTER,
C RESAMPLER
0
COMBINED Y ANTIALIAS, PAL NOTCH FILTERS,
Y RESAMPLE
0
–10
–20
–30
–40
–50
–10
ATTENUATION (dB)
AMPLITUDE (dB)
–20
–30
–40
05700-021
–70
0
2
4
6
8
10
12
FREQUENCY (MHz)
–60
0
1
2
3
4
5
6
FREQUENCY (MHz)
Figure 24. Combined Y Antialias, PAL Notch Filters
Figure 26. Chroma Shaping Filter Responses
Rev. G | Page 34 of 120
05700-023
–60
–50
05700-022
–100
AMPLITUDE (dB)
–60
AD [ ANALOG DEVICES ]
