Specifications

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For multiplexing of the sequence, following operation is used:
if (current_position is within FG image area) {
R
DST = RFG
G
DST = GFG
B
DST = BFG
}
else {
R
DST = RBG
G
DST = GBG
B
DST = BBG
}
For alpha blending of above operation, following equation is used:
R
DST = RFG x α + RBG x (1 – α)
G
DST = GFG x α + GBG x (1 – α)
B
DST = BFG x α + BBG x (1 – α)
CORELOGIC
CORELOGIC
Video Image
OSD Image
Image on display device
α
α=0
α=0.5
α=1.0
Figure 4-15. Example of Alpha-blending
Where RBG, GBG and BBG are color components of image that is calculated in
previous operation step, while R
FG, GFG and BFG are color components for image of
current layer. There is four bit fixed-point arithmetic value and its range is 0 to 1.
During the operation, for TV output case, the video image for the process is scaled
to 2X in direction of both.