VDP 31xxB
PRELIMINARY DATA SHEET
cross-color components, as well as cross-luminance.
The loss of vertical resolution in the luminance channel
is compensated by adding the vertical detail signal with
removed color information.
2.3.8. Luminance Notch Filter
If a composite video signal is applied, the color informa-
tion is suppressed by a programmable notch filter. The
position of the filter center frequency depends on the
subcarrier frequency for PAL/NTSC. For SECAM, the
notch is directly controlled by the chroma carrier fre-
quency. This considerably reduces the cross-lumi-
nance. The frequency responses for all three systems
are shown in Fig. 2–10.
CVBS
Luma
Y
Notch
filter
Y
8
8
Chroma
Chroma
Process.
Chroma
Process.
C C
r
C C
r
b
b
8
dB
10
a) conventional
b) S-VHS
CVBS
0
Notch
filter
Y
8
–10
Chroma
1 H
C C
r
b
–20
–30
Process.
Delay
c) compensated
–40
MHz
Notch
filter
Y
0
2
4
6
8
10
CVBS
1 H
Delay
PAL/NTSC notch filter
8
dB
10
C C
r
b
Chroma
Process.
0
d) comb filter
–10
Fig. 2–7: NTSCcolor decoding options
–20
–30
–40
CVBS
Notch
filter
MHz
Y
0
2
4
6
8
10
8
SECAM notch filter
Chroma
Process.
1 H
Delay
C C
r
b
Fig. 2–10: Frequency responses of the luma
notch filter for PAL, NTSC, and SECAM
a) conventional
Luma
Y
2.3.9. Skew Filtering
8
The system clock is free-running and not locked to the
TV line frequency. Therefore, the ADC sampling pattern
Chroma
Chroma
Process.
1 H
Delay
C C
r
b
8
is not orthogonal. The decoded YC C signals are con-
verted to an orthogonal sampling raster by the skew fil-
ters, which are part of the scaler block.
r
b
b) S-VHS
Fig. 2–8: PAL color decoding options
The skew filters allow the application of a group delay to
the input signals without introducing waveform or fre-
quency response distortion.
CVBS
Notch
filter
Y
8
The amount of phase shift of this filter is controlled by the
horizontal PLL1. The accuracy of the filters is 1/32
clocks for luminance and 1/4 clocks for chroma. Thus
MUX
Chroma
Process.
1 H
Delay
C C
r
b
the 4:2:2 YC C data is in an orthogonal pixel format
r
b
even in the case of nonstandard input signals such as
VCR.
Fig. 2–9: SECAM color decoding
12
Micronas
MICRONAS [ MICRONAS ]
