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46 2 Hybrid Video Coding
n
0
n
1
p
n
0
p
n
1
n
0
p
n
1
n
0
p
n
1
(a) (b) (c) (d)
Figure 2.15 Four gradient patterns used in SAO. Sample labeled p indicates a center pixel to be
considered. Two pixels labeled n
0
and n
1
specify two neighboring pixels along the (a) horizontal,
(b) vertical, (c) 135 diagonal, and (d) 45 gradient patterns.
Table 2.2 Pixel edge categories in the SAO edge offset mode.
Edge Category Condition Meaning
0 Cases not listed below Monotonic area
1 p < n
0
and p < n
1
Local min
2 p < n
0
and p = n
1
or p < n
1
and p = n
0
Edge
3 p > n
0
and p = n
1
or p > n
1
and p = n
0
Edge
4 p > n
0
and p > n
1
Local max
efficient. In summary, SAO is a nonlinear filtering operation which ...