NEC µPD72257 Preliminary User's Manual page 163

Video Input (Ravin-M only)
6.4.2.2
Note
xremainder = 1 - xsum
xadd = xadd - xremainder
Cxout(xout) = Cxout[xout] + Cyout[xin] • xremainder
Figure 6-6
6.4.2.3
Example
X-scaler
The x-scaler allows up- and downscaling of a scanline.
The x scaling factor is determined by VInSCALING.MX[6:0] and is calculated as
x_scale = VInSCALING.MX[6:0] / 64
MX[6:0] > 64 performs an upscaling, MX < 64 a downscaling. If MX = 0, the x-
scaler is disabled.
Depending on the scaling factor MX/64 a certain number of weighted input pixel
Pyout[x] contribute to the output pixel Pxout[x] at location x:
Pxout[x] = w • Pyout
1
whereas the sum of all weighting factors w
The below flow diagram describes the x-scaling process. The shown scaling
process is done for each of the three colour components R, G and B.
The x-scaling process is initialized and started with each new scanline.
Pyout[xin] includes the three colour channels C, i.e. is R or G or B.
Pyout[xin]
from y-scaler
xadd = x_scale
no
xadd + xsum ≥ 1?
yes
output Cxout[xout] to position xout
Cxout[xout] = 0
xsum = 0
pixel output
Video Input x-scaler
Example
In the above example the scaled image shall have a size of (600 x 225) pixels, thus
VInSCALEDWIDTH = 0000 0258
The scaled image shall be generated by scaling a rectangle of the size (512 x 300)
pixels from the captured image. Therefore the x-scaling factor is 600/512 = 75/64
(VInSCALING.MX[6:0] = 75), and the y-scaling factor 300/225 = 48/64
(VInSCALING.MY[5:0] = 48). i.e. VInSCALING = 3040 4B40
64 is fixed.
Preliminary User's Manual S19203EE1V3UM00
+ w • Pyout + ... + w
1 2 2
for the input pixel Pyout
n
next_pixel
to y-scaler
no pixel output
Cxout[xout] = Cxout[xout] + Cyout[xin] • xadd
xsum = xsum + xadd
Pyout[xin] include the colour channels C
with C = R or G or B
and VInSCALEDHEIGHT = 0000 00E1
H
Chapter 6
• Pyout
n n
equals 1.
n
H
. Note that the divisor
H
.
163