
PRODUCT SPECIFICATION
TMC22x5yA
43
The TMC22x5yA Comb Filter 
Architecture
The TMC22x5yA, when implementing a line based comb 
filter, has a core architecture as shown in Figure 10. The con-
cept of the complementary bandsplit filter is also observed in 
the complementary comb filter architecture. It is therefore 
possible to adapt between the complementary comb filter 
and bandsplit filter without throwing away any of the 
original composite video frequency spectrum. 
The first step in the complementary comb filter is to separate 
the high frequency luminance from the chrominance signal. 
This combed high frequency luma signal is shown as 
YCOMB
 in Figure 10. The second step is to produce an array 
of comb filter error signals that indicate the degree of confi-
dence that the 
YCOMB
 signal is just the high frequency luma 
and not a combination of high frequency luma and chroma 
smeared over the number of lines used in the comb filter. The 
signal representing this degree of confidence is termed “K” 
in Figure 10. The last step is to provide a complementary 
cross fade between the 
YCOMB
 signal and the output of the 
complementary bandsplit filter, shown as 
SIMPLE
 in Figure 
10. The 
FLAT
 signal is simply a delayed version of the input 
to the comb filter, therefore the sum of 
Output1
 and 
Output2
will always be equal to the 
FLAT
 video input.
The TMC22x53A comb filter architecture has three taps. 
These taps are three consecutive field lines in a line based 
comb, three consecutive picture lines in a field based comb, 
or lines that are one frame and one field line apart in the 
frame based comb. In addition to these different inputs to the 
comb filter, NTSC and PAL video signals comb over differ-
ent taps in different architectures, as described in the comb 
filter introduction.
The total internal pipeline latency is 1H + 40 pixels for 3 line 
comb filters, for all other comb filter and simple decoder 
architectures the pipeline latency is 40 pixels.
Figure 10. TMC22x5yA Line Based Comb Filter Architecture
Input
Output1
Output2
1H
1H
Bandsplit
Filters
COMB
Filter
XLUT
XLUT
SIMPLE
YCOMB
Simple +/- {k * Ycomb}
K
X
+
–