VDP 31xxB
PRELIMINARY DATA SHEET
2.8.3. Dynamic Peaking
The center frequency of the peaking filter is switchable
from 2.5 MHz to 3.2 MHz. For S-VHS and for notch filter
color decoding, the total system frequency responses
for both PAL and NTSC are shown in figure 2–16.
Especiallywithdecodedcompositesignalsandnotchfil-
ter luminance separation, as input signals, it is neces-
sary to improve the luminance frequency characteris-
tics. With transparent, high-bandwidth signals, it is
sometimes desirable to soften the image.
Transients, produced by the dynamic peaking when
switching video source signals, can be suppressed via
the priority bus.
IntheVDP31xxB, thelumaresponseisimprovedby‘dy-
namic’ peaking. The algorithm has been optimized re-
garding step and frequency response. It adapts to the
amplitude of the high frequency part. Small AC ampli-
tudes are processed, while large AC amplitudes stay
nearly unmodified.
dB
20
15
10
5
0
The dynamic range can be adjusted from *14 to
)14 dB for small high frequency signals. There is sepa-
rate adjustment for signal overshoot and for signal un-
dershoot. For large signals, the dynamic range is limited
by a non-linear function that does not create any visible
alias components. The peaking can be switched over to
“softening” by inverting the peaking term by software.
–5
–10
–15
–20
MHz
0
2
4
6
8
10
Fig. 2–15: Dynamic peaking frequency response
dB
20
dB
20
CF= 2.5 MHz
15
15
CF= 3.2 MHz
10
10
5
5
0
0
S-VHS
–5
–5
–10
–15
–10
–15
–20
MHz
–20
MHz
0
2
4
6
8
10
0
2
4
6
8
10
dB
dB
20
15
10
20
CF= 3.2 MHz
CF= 2.5 MHz
15
10
5
0
5
0
PAL/SECAM
–5
–5
–10
–10
–15
–20
–15
–20
MHz
MHz
0
2
4
6
8
10
0
2
4
6
8
10
dB
dB
20
15
10
20
15
10
CF= 2.5 MHz
CF= 3.2 MHz
5
0
5
0
NTSC
–5
–5
–10
–10
–15
–20
–15
–20
MHz
MHz
0
2
4
6
8
10
0
2
4
6
8
10
Fig. 2–16: Total frequency response for peaking filter and S-VHS, PAL, NTSC
16
Micronas
MICRONAS [ MICRONAS ]
