Digital Signal Processing Reference
In-Depth Information
Figure 6.5. (a) Noisy. Denoised based on (b) MS-VST + starlet, (c) Anscombe VST, and (d)
Haar-Fisz VST.
apply the VST on the approximation coefficients
c
j
, leading to the following scheme
(see also the block diagram of Fig. 6.6):
UWT
c
j
=
c
j
=
MS-VST
+
UWT
h
↑
j
−
1
h
↑
j
−
1
c
j
−
1
c
j
−
1
a
j
−
1
=⇒
(6.39)
g
↑
j
−
1
g
↑
j
−
1
w
j
=
w
j
=
A
j
−
1
(
c
j
−
1
)
e
(
j
)
)
b
(
j
)
sign(
c
j
+
, and
b
(
j
)
and
e
(
j
)
are defined as in
where
A
j
(
c
j
)
=
|
c
j
+
e
(
j
)
|
equation (6.36).
Asymptotic normality of MS-VST
UWT detail coefficients was also proved
by Zhang et al. (2008b) with an asymptotic variance that does not depend on the
underlying intensity:
+
2
j
)
w
j
[
k
]
∼N
(0
,σ
,
(6.40)
