Digital Signal Processing Reference
In-Depth Information
threshold
threshold
0.8
0.8
probability
0.0
0.0
probability
r(n)
r(n)
0
50
100
150
200
0
50
100
150
200
samples
samples
(a) Onset with irregular pulses
(b) High fundamental frequency vowel, 'o'
s(n)
s(n)
threshold
0.8
threshold
0.0
probability
0.8
0.0
probability
r(n)
r(n)
0
100
200
300
400
0
100
200
300
400
samples
samples
(d) Resonance at the nasal sound 'ng'
(c) Resonance at the nasal sound 'nd'
Figure 9.6
Some instances of difficult pitch pulse extraction
found recursively, with any
n
q
which have already satisfied equation (9.11)
taken as
n
l
in the next iteration. If more than one
n
q
satisfies equation (9.11),
the one which minimizes
n
l
+
n
q
is chosen.
n
l
+
τ
+
τ
+
n
q
<
0
.
15
τ
(9.11)
The final probability of the candidate location
n
p
0
containing a pitch pulse
p
0
is recalculated,
p
0
max
p
p
0
=
(9.12)
A set of positions,
n
p
w
which have probabilities,
p
>
0
.
8, are selected as
the pitch pulse locations, and they are further refined in order to select
the pitch pulse closest to the synthesis frame boundary. Figure 9.6 shows
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