BT835 Ver la hoja de datos (PDF) - Conexant Systems
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BT835 Datasheet PDF : 111 Pages
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2.0 Inputs and Timing
2.2 Digital Video Ports
Bt860/861
Multiport YCrCb to NTSC/PAL /SECAM
2.2.4 Overlay Modes and Alpha Blending
The Bt860/861 can be configured to display only a single video stream, or to mix
any combination of two data ports (P, VID, and OSD). Programming register field
ALPHAMODE (1A[6:5]) to 00 and register bit BLENDMODE (1A[7]) to 1
selects the internal video bus as the sole source of data, regardless of the alpha
source. In this mode, either the VID port or the P port can be used as the video
source, which is selected by register bit VIDEO_SEL (1A[3]). Other
combinations of the ALPHAMODE and BLENDMODE programming will allow
blending of the video and overlay buses. Table 2-1 lists all valid input modes.
Table 2-1. Alpha Blending Configurations
Configuration
Programming
VID
None
None
VID
P
ALPHA[1:0]
VID
P
ALPHA[1:0]
VID
P
ALPHA[1:0]
VID
P
P LSBs
VID
OSD
ALPHA[1:0]
VID
OSD
ALPHA[1:0]
VID
OSD
ALPHA[1:0]
VID
OSD
OSD LSBs
P
None
None
P
OSD
ALPHA[1:0]
P
OSD
ALPHA[1:0]
P
OSD
ALPHA[1:0]
P
OSD
OSD LSBs
NOTE(S): X or XX = Don’t care.
None
1
00
1
1 bit
1
01
1
2 bit
1
10
1
4 bit
1
11
1
2 bit
0
XX
1
1 bit
1
01
1
2 bit
1
10
1
4 bit
1
11
1
2 bit
0
XX
1
None
1
00
0
1 bit
1
01
0
2 bit
1
10
0
4 bit
1
11
0
2 bit
0
XX
0
X
No
0
Yes
0
Yes
0
No
0
Yes
1
Yes
1
Yes
1
No
1
Yes
X
No
1
Yes
1
Yes
1
No
1
Yes
Data from the overlay source may be applied with varying levels of
transparency, from fully transparent, no overlay, to fully opaque, full overlay. A
4-bit blend multiplier provides sixteen levels of mixing. The value 1111 is a
special case allowing the overlay data to pass completely unmixed. In all other
cases the value applied to the video path is (1 – blend / 16), and the value applied
to the overlay path is (blend / 16), where blend is the 4-bit multiplier value.
Two methods are used to generate the 4-bit multiplier. The multiplier value
can come either from a four-entry by 4-bit lookup table (LUT), or directly from
the ALPHA pins. In both cases, the blend multiplier value will be applied to both
luma and chroma for the co-sited components (Cb0:Y0:Cr0) and a separate
multiplier applied for the (Y1) component.
2-4
Conexant
D860DSA
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