DDP3310B Datasheet, PDF (9/60 Pages) Micronas – Display and Deflection Processor

ADVANCE INFORMATION
DDP 3310B
2.1.7. Chroma Interpolation
In case of YC_rC_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_rC_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
Fig. 2–4. All further processing is carried out at the full
sampling rate.
dB
0
-10
-20
-30
-40
-50
MHz
0
4
8
12
16
20
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.
2.1.9. Inverse Matrix and Digital RGB Processing
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:
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_rC_b
input
t
b)
Ampl.
t
c)
C_r out
C_b out
a) C_rC_b input of DTI
t
b) C_rC_b input + correction signal
c) sharpened and limited C_rC_b
Fig. 2–5: Digital color transient improvement
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-
tion 2.2.4. “CRT Measurement and Control”.
R
G
=
MIN
 ^{C----3-T--2--M---}
×
S_----A_--3--T_-2---M_{--- ,}
S_----A_----T_----L_---I_---M_---
32
×
--1---
64
×
MR1M MR2M
MG1M MG2M ^×
Cb
Cr
+


C_-----T_----M_---
32
×
Y_
B
MB1M MB2M
Micronas
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