1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
|
<HTML>
<HEAD>
<TITLE>TSP (libtsp/SP) - SPcorBWexp</TITLE>
</HEAD>
<BODY BGCOLOR="#FFFACD">
<H2>SPcorBWexp</H2>
<HR>
<H4>Routine</H4>
<DL>
<DT>
void SPcorBWexp (double bwexp, const float rxx[], float rxxb[], int Nc)
</DL>
<H4>Purpose</H4>
<DL>
<DT>
Bandwidth expand a set of correlation values
</DL>
<H4>Description</H4>
The procedure forms the bandwidth expanded version of a set of correlation
values. The correlation coefficients are multiplied by a Gaussian function.
This is equivalent to convolving the power spectral density by a Gaussian
function. The bandwidth expansion is measured in terms of the width of
the Gaussian function in the frequency domain. A power spectrum consisting
of spectral lines will have each spectral line converted into a Gaussian
function with this bandwidth.
<P>
The Gaussian function is specified in terms of its normalized bandwidth
(measured at the 1 standard deviation point). The 3 dB bandwidth is
related to the 1 sigma bandwidth by the following relationship.
<PRE>
B3dB = sqrt (2 ln 2) Bsigma = 1.1774 Bsigma
</PRE>
The ITU-T G.729 8 kb/s CS-ACELP speech coder uses a 1 sigma bandwidth
expansion of 60 Hz relative to a sampling rate of 8000 Hz (bwexp = 60/8000
= 0.0075).
<P>
<DL>
<DT>
Reference:
</DL>
Y. Tohkura, F. Itakura, and S. Hashimoto, "Spectral smoothing technique in
PARCOR speech analysis-synthesis", IEEE Trans. Acoustics, Speech, Signal
Proc., vol. ASSP-26, pp. 587-596, Dec. 1978.
<H4>Parameters</H4>
<DL>
<DT>
-> double bwexp
<DD>
Bandwidth expansion factor
<DT>
-> const float rxx[]
<DD>
Input correlation coefficients (Nc values)
<DT>
<- float rxxb[]
<DD>
Output correlation coefficients (Nc values). The output values can
overlay the input values.
<DT>
-> int Nc
<DD>
Number of correlation coefficients
</DL>
<H4>Author / revision</H4>
P. Kabal Copyright (C) 1996
/ Revision 1.1 1996/05/23
<H4>See Also</H4>
<A HREF="SPpcBWexp.html">SPpcBWexp</A>
<P>
<HR>
Main Index <A HREF="../libtsp.html">libtsp</A>
</BODY>
</HTML>
|
