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r=g and b=g,
White balance is adjusted by the voltage of Pin ® and ® of
IC911
and
VR931
and
VR932,.
and
automatically
controlled by PWM output of Pin @ and @ of iC932..
The r, g and b signals after white balance compensation is
limited to the bandwidth required for the chroma signal by
LPF and low level noise component is eliminated by the
slicing circuit, then appropriate gamma
compensation
is
performed by the gamma ( y ) circuit.
in R-Y and B-Y matrix, HUE and GC circuits, R-Y and B-Y
is created using r, g and b signais gamma compensated,
and hue adjustment is done by HUE circuit using following
formulas :
(R-Y)' = (R-Y) + « (B-Y)
(B-Y)' = (B-Y) + B (R-Y)
The GC circuit adjusts each level of (R-Y)' and (B-Y)'.
The hue and level are adjusted by the voltage of Pins@,
@
and © of iC9114.
2-4-4.
YH Processing
2-15
2-5. 1C912 (Fig. 2-23)
2-5-1.
Y Signal Processing
AGC CONT
YH
HAP GAIN
SLICE BLK
EVR
{BURST LEVEL)
B-Y
Fig. 2-23.
11
i
1
i
Yurt BeHae
eee
i
i
FADE
(CONTROL VOLTAGE)
Y LEVEL
eva
Ser UP TEL)
1€912 Biock Diagram
Fig. 2-24.
H Aperture Correction
2-16
2-5-2.
C Signal Processing
The R-Y and B-Y signals from Pins @ and @ are clamped,
added
with
burst flag pulse,
and
passed
through
the
subcarrier modulation and blanking circuits, respectively,
then jevel controlled at:GC block after added each other.
In GC block, the C signal is once output from Pin @ after
suppressed at high luminance section and vertical edge by
CSY (Pin
@® ), suppressed
at low iflumination
by AGC
voltage (Pin @) and attenuated by FADE voltage as Y
signal. After band limited by the external BPF. the C signal
is Input to Pin @ again, and fed from Pin @ to the VTR as
CAN.C after amplified.
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