TMC22x5yA
PRODUCT SPECIFICATION
phase relationship to the chroma on 1H. Therefore normally
0H and 2H are added together to produce the average luma
across 3 lines and this is then subtracted from 1H to produce
the combed chroma.
0H and FR0H and the two consecutive field lines FR0H and
FR1H are 180 degrees apart. The flat color on FR0H and
FR1H can be added or subtracted to provide the luminance
or chrominance to subtract from 0H.
LINE no FIELD 1
FIELD 2 FIELD 3 FIELD 4
I
FIELD LINE no
PAL
U
NTSC
I
283
(1H)
I
Q
Q
N
0
1
0
Q
I
(FR1H)
V
U
21
22
23
24
Q
Q
I
M
(F1H)
I
V
284
285
286
Q
Q
Q
Q
I
N+1
2H
1H
0H
(FR0H)
Q
(0H)
Q
I
Q
(F0H)
Q
I
1
0
M+1
N+2
I
V
Q
I
I
U
V
Q
1
0
M+2
N+3
I
I
U
Q
Q
I
I
I
I
Q
Q
1
0
M+3
N+4
U
I
V
Q
65-22x5y-49
65-22x5y-48
Figure 8. Chrominance Vector Rotation Over 4
Fields in NTSC
Figure 7. Chrominance Vector Rotation in PAL and NTSC
Composite Field-Based Comb Filters
YC Line-Based Comb Filters
In NTSC field based comb decoders, there is an external
delay of 263 lines, therefore the 2 adjacent picture lines 0H
and F0H and the two consecutive field lines F0H and F1H
are 180 degrees apart. The flat color on F0H and F1H can be
added or subtracted to provide the luminance or chromi-
nance to subtract from 0H.
The luminance and chrominance signals, are by definition,
already separated for YC inputs. However, if the original
source was composite, there is a distinct possibility that there
is some residual luminance (cross color) in the chrominance
signal and some residual chrominance (cross luma) in the
luminance signal. It is therefore legitimate to treat these
signals as if they were simply the output from bandsplit
filters and process the luma and chroma signals accordingly.
PAL Field Decoders
D1 Line-Based Comb Filters
Composite, PAL Field Comb Filters
In PAL field based comb decoders, there is an external delay
of 312 lines, therefore the 2 adjacent picture lines 0H and F0H
are 180 degrees apart. In fields 5, 6, 7, and 8 the U and V
vectors are 180 degrees advanced from fields 1, 2, 3, and 4.
A D1 data stream consists of multiplexed Y, C and C
component data. If the original source was composite there
B
R
maybe luminance (cross color) in C C and chrominance
B R
(cross luma) in Y. In the first case any luminance that was
passed through a demodulator along with the chroma to
LINE no FIELD 1 FIELD 2 FIELD 3 FIELD 4
produce the baseband C C color difference signals would
B R
V
U
have the same characteristics as chroma. That is to say, the
cross color would advance by 180° every line in NTSC and
every 2 lines in PAL. It is therefore possible to remove this
cross color in a comb filter. In the latter case any chromi-
nance that is still in theY data can obviously be removed in a
comb filter as well.
U
23
336
24
337
V
U
U
(F0H)
V
U
V
V
(FR0h)
V
(0H)
U
V
U
V
U
V
U
The original source for the D1 signal could also have been
computer graphics. In this case, the comb filter can be used
to remove the picture flicker and convert the output to RGB.
U
U
(FR0H)
V
V
U
25
338
26
U
V
V
U
V
NTSC Frame and Field Based
Decoders
65-22x5y-50
Figure 9. Chrominance Vector Rotation
Over 4 Fields in PAL
Composite Frame-Based Comb Filters
In NTSC the chrominance vectors advance by 180 degrees
every line, therefore after 525 lines the 2 adjacent frame lines
42
REV. 1.0.0 2/4/03
CADEKA [ CADEKA MICROCIRCUITS LLC. ]
