ADV7180
NTSC Comb Filter Settings
COMB FILTERS
Used for NTSC M/J CVBS inputs.
The comb filters of the ADV7180 have been greatly improved to
automatically handle video of all types, standards, and levels of
quality. The NTSC and PAL configuration registers allow the
user to customize comb filter operation, depending on which
video standard is detected (by autodetection) or selected (by
manual programming). In addition to the bits listed in this
section, there are some further internal controls (based on
Analog Devices proprietary algorithms); contact local Analog
Devices field engineers for more information.
NSFSEL[1:0], Split Filter Selection NTSC, Address 0x19
[3:2]
The NSFSEL[1:0] control selects how much of the overall signal
bandwidth is fed to the combs. A narrow split filter selection
results in better performance on diagonal lines, but more dot
crawl in the final output image. The opposite is true for selecting
a wide bandwidth split filter.
Table 49. NSFSEL Function
NSFSEL[1:0]
Description
Narrow
00 (default)
01
10
11
Medium
Medium
Wide
CTAPSN[1:0] Chroma Comb Taps NTSC, Address 0x38 [7:6]
Table 50. CTAPSN Function
CTAPSN[1:0]
Description
00
Do not use
01
NTSC chroma comb adapts three lines (three taps) to two lines (two taps)
NTSC chroma comb adapts five lines (five taps) to three lines (three taps)
NTSC chroma comb adapts five lines (five taps) to four lines (four taps)
10 (default)
11
CCMN[2:0] Chroma Comb Mode NTSC, Address 0x38 [5:3]
Table 51. CCMN Function
CCMN[2:0]
Description
Configuration
0xx (default)
Adaptive comb mode
Adaptive 3-line chroma comb for CTAPSN = 01
Adaptive 4-line chroma comb for CTAPSN = 10
Adaptive 5-line chroma comb for CTAPSN = 11
100
101
Disable chroma comb
Fixed chroma comb (top lines of line memory)
Fixed 2-line chroma comb for CTAPSN = 01
Fixed 3-line chroma comb for CTAPSN = 10
Fixed 4-line chroma comb for CTAPSN = 11
Fixed 3-line chroma comb for CTAPSN = 01
Fixed 4-line chroma comb for CTAPSN = 10
Fixed 5-line chroma comb for CTAPSN = 11
Fixed 2-line chroma comb for CTAPSN = 01
Fixed 3-line chroma comb for CTAPSN = 10
Fixed 4-line chroma comb for CTAPSN = 11
110
111
Fixed chroma comb (all lines of line memory)
Fixed chroma comb (bottom lines of line memory)
Rev. A | Page 38 of 112
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