VDP 313xY
ADVANCE INFORMATION
2.4.9. Luminance Notch Filter
CVBS
Notch
filter
Y
If a composite video signal is applied, the color infor-
mation 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 chrominance car-
rier frequency. This considerably reduces the
cross-luminance. The frequency responses for all
three systems are shown in Fig. 2–8.
8
Chroma
Process.
1H
Delay
CRCB
a) conventional
Luma
Y
8
Chroma
dB
10
Chroma
Process.
1H
Delay
CRCB
8
0
b) S-VHS
–10
Fig. 2–6: PAL color decoding options
–20
–30
CVBS
Notch
filter
–40
Y
MHz
0
2
4
6
8
10
8
PAL/NTSC notch filter
MUX
Chroma
Process.
1H
Delay
CRCB
dB
10
Fig. 2–7: SECAM color decoding
0
–10
–20
–30
–40
MHz
0
2
4
6
8
10
SECAM notch filter
Fig. 2–8: Frequency responses of the luminance
notch filter for PAL, NTSC, SECAM
2.4.10.Skew Filtering
The system clock is free-running and not locked to the
TV line frequency. Therefore, the ADC sampling pat-
tern is not orthogonal. The decoded YCRCB signals
are converted to an orthogonal sampling raster by the
skew filters, which are part of the scaler block.
The skew filters allow the application of a group delay
to the input signals without introducing waveform or
frequency response distortion.
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 chrominance.
Thus the 4:2:2 YCRCB data is in an orthogonal pixel
format even in the case of nonstandard input signals
such as VCR.
12
Micronas
MICRONAS [ MICRONAS ]
