Databases Reference
In-Depth Information
a
b
b
1
b
2
b
3
b
4
b
11
b
12
b
13
b
14
b
21
b
22
b
23
b
24
d
c
b
31
b
32
b
33
b
34
b
41
b
42
b
43
b
44
II
I
V
III
IV
VI
VII
F I GU R E 16 . 11
Data structure used in the SPIHT algorithm.
or four, the size of
D
(
i
,
j
)
is either zero or a sum of powers of four.
H
This is the set of all root nodes—essentially Band I in the case of Figure
16.11
.
L
(
i
,
j
)
This is the set of coordinates of all the descendants of the coefficient at location
(
i
,
j
)
except for the immediate offsprings of the coefficient at location
(
i
,
j
)
. In other
words,
L
(
i
,
j
)
= D
(
i
,
j
)
− O
(
i
,
j
)
In Figure
16.11
the set
L
(
0
,
1
)
consists of the coordinates of the coefficients
b
11
,...,
b
14
,...,
b
44
.
is said to be significant if any coefficient in the set has a magnitude
greater than the threshold. Finally, thresholds used for checking significance are powers of
two, so in essence the SPIHT algorithm sends the binary representation of the integer value of
Aset
D
(
i
,
j
)
or
L
(
i
,
j
)
