ADVANCE INFORMATION
2.1.7. Chroma Interpolation
In case of YC
r
C
b
4:1:1 input format, an interpolation fil-
ter is used which converts the digital input signal to
4:2:2 format. This filter runs with the incoming pixel
clock frequency.
The signal is passed to the scaler in YC
r
C
b
4:2:2 for-
mat in order to convert the incoming pixel clock fre-
quency (27/32 MHz) to the internal frequency (40.5/
40 MHz). A linear phase interpolator is used to convert
the chroma sampling rate from 4:2:2 to 4:4:4.
The frequency response of the interpolator is shown in
sampling rate.
0
dB
-10
-20
-30
-40
-50
0
4
8
12
16
20
MHz
Fig. 2–4:
Frequency response of the chroma 4:2:2 to
4:4:4 interpolation filter
2.1.8. Chroma Transient Improvement
The intention of this block is to enhance the chroma
resolution. A correction signal is calculated by differen-
tiation of the color difference signals. The differentia-
tion can be selected according to the signal bandwidth,
e.g. for PAL/NTSC/SECAM or digital component sig-
nals, respectively. The amplitude of the correction sig-
nal is adjustable. Small noise amplitudes in the correc-
tion signal are suppressed by an adjustable coring
circuit. To eliminate “wrong colors”, which are caused
by over and undershoots at the chroma transition, the
sharpened chroma signals are limited to a proper
value automatically.
a)
C
r
C
b
input
t
b)
Ampl.
t
2.1.9. Inverse Matrix and Digital RGB Processing
c)
Six multipliers in parallel perform the matrix multiplica-
tion to transform the C
r
and C
b
signals to R
−
Y, B
−
Y,
and G
−
Y. The initialization values for the matrix are
computed from the standard ITU-R (CCIR) matrix:
C
r
out
C
b
out
R
1
0
1,402
Y
G
= 1 – 0,345 – 0,713
×
Cb
B
1 1,773
0
Cr
The multipliers are also used to adjust color saturation
and picture contrast. Since the multiplier allows
±
4 as
the biggest coefficient, it is possible that the product of
CTM
×
SATM
×
MxxM will be clipped, which causes
wrong colors. SATLIM limits the product of contrast
times saturation to allow a maximum oversaturation.
The matrix computes:
a) C
r
C
b
input of DTI
b) C
r
C
b
input
+
correction signal
c) sharpened and limited C
r
C
b
Fig. 2–5:
Digital color transient improvement
t
After adding the post-processed luma, the digital RGB
signals are limited to 10 bits. Three multipliers are
used to digitally adjust the white-drive and to imple-
ment an average beam current limiter. See also Sec-
R
MR1M MR2M
1
Cb
+
CTM
×
Y
CTM SATM
SATLIM
×
-----
×
-
------------
-
-
-
-
64
MG1M MG2M
×
G
=
MIN
------------
×
---------------
,
---------------------
32
32
32
32
Cr
B
MB1M MB2M
Micronas
9
MICRONAS [ MICRONAS ]
