For filtering of the lines to generate the output lines only the luminance values Y
of the pixel is regarded. Thus Y is calculated for each pixel and stored in the line
buffer Ylinebuf[1023:0]. For the Y calculation the colour components contribute
in the relation R:G:B = 1:2:1.
Depending on the scaling factor MY/64 with MY < 64 a number lines do not
produce output lines, but their Y values in Ylinebuf[1023:0] impact the values of
lines, which generate output.
If a line output has to be generated, the colour components R, G, B of the output
pixel Pyout[xin] are calculated and their values are clamped to 8 bit resolution, i.e.
to the range 0 to FF
H
.
Pyout[xin] is handed over to the x-scaler.
Note
Pin[xin] and Pyout[xin] includes the three colour channels R, G, B.
frame end?
no
yes
yes
y = y +1
xin = 0
yadd = y_scale
frame end?
no
yes
y = y +1
new frame
line end?
no
no line output
no
yes
ysum = ysum + yadd
xin = xin +1
read pixel Pin[xin]
Y = R + 2G + B
Ylinebuf[xin] = Ylinebuf[xin] + Y
•
yadd
reset y-scaler:
y_scale = MY/64
ysum = 0
Ylinebuf[1023:0] = 0
y = 0
yadd + ysum
≥
1?
line end?
line output
no
yes
from x-scaler:
next_pixel
xin = xin +1
read pixel Pin[xin]
Y = R + 2G + B
Ylinebuf[x] = Ylinebuf[xin] + Y
•
yremainder
delta = Ylinebuf[xin] - Y
R = R + delta
G = G + delta
B = B + delta
Pyout[xin] = clamp(RGB)
clamp(RGB): with C = R or G or B
- if C < 0:
C := 0
- if C > 255:
C := 255
output pixel Pyout[xin]
to x-scaler
reset x-scaler:
x_scale = MX/64
xsum = 0
yremainder = 1 - ysum
yadd = yadd - yremainder
Figure 6-5 Video Input y-scaler
Chapter 6
Video Input (Ravin-M only)
162
Preliminary User's Manual S19203EE1V3UM00
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