ADVANCE INFORMATION
VCT 38xxA
2.4.7. Automatic Standard Recognition
CVBS
Luma
Y
Y
Notch
filter
8
8
chroma
8
The burst-frequency measurement is also used for
automatic standard recognition (together with the sta-
tus of horizontal and vertical locking) thus allowing a
completely independent search of the line and color
standard of the input signal. The following standards
can be distinguished:
Chroma
Process.
Chroma
C C
C C
r
r
b
b
Process.
a) conventional
b) S-VHS
CVBS
Y
Notch
filter
8
PAL B,G,H,I; NTSC M; SECAM; NTSC 44; PAL M;
PAL N; PAL 60
1 H
Chroma
C C
r
b
Delay
Process.
For a preselection of allowed standards, the recogni-
tion can be enabled/disabled via I2C bus for each stan-
dard separately.
c) compensated
Notch
filter
Y
CVBS
If at least one standard is enabled, the VCT 38xxA reg-
ularly checks the horizontal and vertical locking of the
input signal and the state of the color killer. If an error
exists for several adjacent fields a new standard
search is started. Depending on the measured line
number and burst frequency, the current standard is
selected.
1 H
Delay
8
C C
r
b
Chroma
Process.
d) comb filter
For error handling the recognition algorithm delivers
the following status information:
Fig. 2–6: NTSC color decoding options
– search active (busy)
– search terminated, but failed
– found standard is disabled
– vertical standard invalid
– no color found
CVBS
Y
Notch
filter
8
1 H
Delay
Chroma
Process.
C C
r
b
a) conventional
Luma
Y
8
2.4.8. PAL Compensation/1-H Comb Filter
Chroma
1 H
Delay
Chroma
Process.
C C
r
The color decoder uses one fully integrated delay line.
Only active video is stored.
b
8
b) S-VHS
The delay line application depends on the color stan-
dard:
Fig. 2–7: PAL color decoding options
– NTSC:
– PAL:
1-H comb filter or color compensation
color compensation
CVBS
Y
Notch
– SECAM: crossover switch
filter
8
In the NTSC compensated mode, (Fig. 2–6c), the color
signal is averaged for two adjacent lines. Thus,
cross-color distortion and chroma noise is reduced. In
the NTSC comb filter mode, (Fig. 2–6d), the delay line
is in the composite signal path, thus allowing reduction
of cross-color components, as well as cross-lumi-
nance. The loss of vertical resolution in the luminance
channel is compensated by adding the vertical detail
signal with removed color information.
MUX
1 H
Delay
Chroma
Process.
C C
r
b
Fig. 2–8: SECAM color decoding
Micronas
15
MICRONAS [ MICRONAS ]
