
PRODUCT SPECIFICATION
TMC22x5yA
47
Adaptive Comb Filter
The IPCF[1:0] register bits select the inputs to the adaptive 
comb filter, this would normally be xHH for chroma combs, 
xHF for luma combs, and xHL if the luminance signal was to 
be sampled dropped on the output of the TMC22x5yA. The 
Gaussian filters in the sample drop mode already limit the 
chrominance bandwidth to 1.3MHz allowing a [2:1:1] data 
format on the output, with the luminance signal having been 
vertically filtered by a fixed 3 line comb filter.
The SIMP selection bit is an internally generated signal 
based upon the comb filter selected. If a 3 line chroma, luma, 
or D1 comb filter is selected, due to the internal 1H delay 
inherent with this type of comb filter, the 1HL and 1HH 
signals are selected for the respective luma and chroma 
SIMPLE
 data signals. When any other type of comb filter is 
selected 0HL and 0HH are selected.
The DLYF selection bit is also internally generated from the 
type of comb filter selected and whether or not the input is in 
either the YC or Y & CbCr (ie D1 input) data formats. The 
VIDEOB
 data is always selected when the YCCOMP register 
bit is HIGH, ie for YC inputs. The selection of 1HF or 0HF 
depends upon the SIMP selection bit only when the 
YCCOMP register bit is LOW. Therefore, when YCCOMP is 
LOW and 0Hx is selected by SIMP then 0HF is selected for 
the 
FLAT
 signal, and when 1Hx is selected by SIMP then 
1HF is selected for the 
FLAT
 signal. This ensures that the 
FLAT
 and 
SIMPLE
 data selected for any comb filter is 
delayed by the same amount as the data processed through 
the comb filter to produce the 
COMB
 output.
The final selection is the output required for the combed 
luminance and chrominance data. The output selection can 
be 
SIMPLE
, 
COMB
, 
FLAT-COMB
, or
 FLAT
. Generally
COMB
 is selected based upon whether a luma or chroma 
comb was selected and the complementary output selects 
FLAT-COMB
. In the YC and Y & CbCr data modes the 
FLAT
signal selects the secondary data and 
SIMPLE
 or 
COMB
 can 
be used to select the primary signal. In these modes the 
bandsplit filter can be bypassed or used to remove low fre-
quency noise from the chrominance signal if chroma was 
selected as the primary signal.
Figure 16. Signal Flow Around the Adaptive Comb Filter.
SIMP
IPCF[1:0]
OHF
OHH
OHL
1HF
1HH
1HL
2HF
2HH
2HL
VideoB
IPCF[1:0]
YMUX[1:0]
Y Data
C Data
65-22x5y-57
CMUX[1:0]
Adaptive
Comb
Filter
IPCF[1:0]
SIMP
A
B
C
D
A
A: Comb
B: Simple
C: Flat - Comb
D: Flat
B
C
D
DLYF
2:1
MUX
2:1
MUX
3:1
MUX
3:1
MUX
–
3:1
MUX
3:1
MUX
4:1
MUX
4:1
MUX