adv7188 Analog Devices, Inc., adv7188 Datasheet - Page 18

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

ADV7188
Fast Blank Edge Shaping
FB_EDGE_SHAPE [2:0], Address 0xEF [2:0]
To improve the picture transition for high speed fast blank
switching, an edge-shaping mode is available on the ADV7188.
Depending on the format of the RGB inputs, it may be advan-
tageous to apply different levels of edge shaping. The levels are
selected via the FB_EDGE_SHAPE [2:0] bits. Users are advised
to try each of the settings and select the setting that is most
visually pleasing on their system.
Table 13. FB_EDGE_SHAPE [2:0] Function
FB_EDGE_SHAPE [2:0]
000
001
010 (default)
011
100
101 to 111
Contrast Reduction
For overlay applications, text can be more readable if the
contrast of the video directly behind the text is reduced. To
enable the definition of a window of reduced contrast behind
inserted text, the signal applied to the FB pin can be interpreted
as a trilevel signal, as shown in Figure 10.
CVBS
Description
No edge shaping
Level 1 edge shaping
Level 2 edge shaping
Level 3 edge shaping
Level 4 edge shaping
Not valid
ADC0
FAST BLANK
(FB PIN)
R
G
B
ADC1
ADC2
ADC3
CLAMPING AND
CONDITIONING
DECIMATION
SIGNAL
FAST BLANK
RESOLVER
POSITION
CLAMPING AND
CONDITIONING
DECIMATION
Figure 9. Fast Blanking Configuration
SIGNAL
EXTRACTION
Rev. A | Page 18 of 112
TIMING
CONVERSION
YPrPb
RGB
≥
PROCESSING
Contrast Reduction Enable
CNTR_ENABLE, Address 0xEF [3]
This bit enables the contrast reduction feature and changes the
meaning of the signal applied to the FB pin.
0 (default)—The contrast reduction feature is disabled, and the
fast blank signal is interpreted as a bilevel signal.
1—The contrast reduction feature is enabled, and the fast blank
signal is interpreted as a trilevel signal.
Contrast Mode
CNTR_MODE [1:0], Address 0xF1 [3:2]
The contrast level in the selected contrast reduction box is
selected using the CNTR_MODE [1:0] bits.
Table 14. CNTR_MODE [1:0] Function
CNTR_MODE [1:0]
00 (default)
01
10
11
VIDEO
RGB SOURCE
100%
CVBS SOURCE
50% CONTRAST
CVBS SOURCE
100%
Figure 10. Fast Blank Signal Representation with
SUBPIXEL
BLENDER
YPrPb
CONTROL
Contrast Reduction Enabled
I
2
C
FORMATTER
OUTPUT
SANDCASTLE
Description
25%
50%
75%
100%