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Recommendation H.261
(03/93)
5
T 150 24 41-9 0/ d0 3
C C
T
Q
Q
T
F
P
p
t
q z
q
v
f
T
Q
P
F
C C
p
t
q z
q
v
f
V id e o
in
T o vide o
m ultip lex
co de r
T r a ns fo rm
Q ua n tizer
P ictu r e m e m or y with m o tio n com p en sa te d var iab le de lay
L o op f ilte r
C o d in g co nt ro l
F la g fo r IN T R A /IN T E R
F la g fo r tr an sm itte d o r no t
Q ua n tizer in d ic atio n
Q ua n tizing in de x f or t ra n sfo rm coe ff icie n ts
M o tio n v ect or
S w itch in g o n/ off o f t he lo op f ilte r
- 1
- 1
FIGURE 3/H.261
Source coder
FIGURE 3/H.261...[D03] = 16 CM
3.2.3
Loop filter
The prediction process may be modified by a two-dimensional spatial filter (FIL) which operates on pels within a predicted 8
by 8 block.
The filter is separable into one-dimensional horizontal and vertical functions. Both are non-recursive with coefficients of 1/4,
1/2, 1/4 except at block edges where one of the taps would fall outside the block. In such cases the 1-D filter is changed to
have coefficients of 0, 1, 0. Full arithmetic precision is retained with rounding to 8 bit integer values at the 2-D filter output.
Values whose fractional part is one half are rounded up.