adv7188 Analog Devices, Inc., adv7188 Datasheet - Page 34

• Manufacturer Part Number: adv7188
• Description: Multiformat Sdtv Video Decoder With Fast Switch Overlay Support
• Manufacturer: Analog Devices, Inc.

ADV7188
CHROMA FILTER
Data from the digital fine-clamp block is processed by three sets
of filters. The data format at this point is CVBS for CVBS
inputs, chroma only for Y/C, or Cr/Cb interleaved for YPrPb
input formats.
•
•
•
Figure 20 shows the overall response of all filters, from SH1
(narrowest) to SH5 (widest), in addition to the wideband
mode (in red).
Chroma Antialias (CAA) Filter. The ADV7188 oversamples
the CVBS by a factor of 2 and the chroma or Cr/Cb by a
factor of 4. CAA, a decimating filter, 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 (CSH) Filters. These filters can be
programmed to perform a variety of low-pass responses.
They can be used to selectively reduce the bandwidth of the
chroma signal for scaling or compression.
Digital Resampling Filter. This filter 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.
–10
–20
–30
–40
–50
–60
–70
0
0
Figure 19. Y NTSC Notch Filter Responses
2
COMBINED Y ANTIALIAS, NTSC NOTCH FI LTERS,
4
FREQUENCY (MHz)
Y RESAMPLE
6
8
1
0
1
2
Rev. A | Page 34 of 112
CSFM [2:0], C-Shaping Filter Mode, Address 0x17 [7:5]
The C-shaping filter mode bits allow the user to select from a
range of low-pass filters for the chrominance signal.
Table 38. CSFM [2:0] Function
CSFM [2:0]
000 (default)
001
010
011
100
101
110
111
–10
–20
–30
–40
–50
–60
0
0
Figure 20. Chroma-Shaping Filter Responses
1
Description
1.5 MHz bandwidth filter
2.17 MHz bandwidth filter
SH1
SH2
SH3
SH4
SH5
Wideband mode
COMBINED C ANTIALIAS, C-SHAPING FILTER,
2
FREQUENCY (MHz)
C RESAMPLER
3
4
5
6