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comparison spandsp-0.0.3/spandsp-0.0.3/src/spandsp/awgn.h @ 5:f762bf195c4b

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import spandsp-0.0.3
author Peter Meerwald <pmeerw@cosy.sbg.ac.at>
date Fri, 25 Jun 2010 16:00:21 +0200
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4:26cd8f1ef0b1 5:f762bf195c4b
1 /*
2 * SpanDSP - a series of DSP components for telephony
3 *
4 * awgn.h - An additive Gaussian white noise generator
5 *
6 * Written by Steve Underwood <steveu@coppice.org>
7 *
8 * Copyright (C) 2001 Steve Underwood
9 *
10 * All rights reserved.
11 *
12 * This program is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU General Public License version 2, as
14 * published by the Free Software Foundation.
15 *
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
20 *
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, write to the Free Software
23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24 *
25 * $Id: awgn.h,v 1.8 2006/10/24 13:45:27 steveu Exp $
26 */
27
28 /*! \file */
29
30 /* This code is based on some demonstration code in a research
31 paper somewhere. I can't track down where I got the original from,
32 so that due recognition can be given. The original had no explicit
33 copyright notice, and I hope nobody objects to its use here.
34
35 Having a reasonable Gaussian noise generator is pretty important for
36 telephony testing (in fact, pretty much any DSP testing), and this
37 one seems to have served me OK. Since the generation of Gaussian
38 noise is only for test purposes, and not a core system component,
39 I don't intend to worry excessively about copyright issues, unless
40 someone worries me.
41
42 The non-core nature of this code also explains why it is unlikely
43 to ever be optimised. */
44
45 #if !defined(_AWGN_H_)
46 #define _AWGN_H_
47
48 /*! \page awgn_page Additive white gaussian noise (AWGN) generation
49
50 \section awgn_page_sec_1 What does it do?
51 Adding noise is not the most useful thing in most DSP applications, but it is
52 awfully useful for test suites.
53
54 \section awgn_page_sec_2 How does it work?
55
56 This code is based on some demonstration code in a research paper somewhere. I
57 can't track down where I got the original from, so that due recognition can be
58 given. The original had no explicit copyright notice, and I hope nobody objects
59 to its use here.
60
61 Having a reasonable Gaussian noise generator is pretty important for telephony
62 testing (in fact, pretty much any DSP testing), and this one seems to have
63 served me OK. Since the generation of Gaussian noise is only for test purposes,
64 and not a core system component, I don't intend to worry excessively about
65 copyright issues, unless someone worries me.
66
67 The non-core nature of this code also explains why it is unlikely to ever be
68 optimised.
69 */
70
71 /*!
72 AWGN generator descriptor. This contains all the state information for an AWGN generator.
73 */
74 typedef struct
75 {
76 double rms;
77 long int ix1;
78 long int ix2;
79 long int ix3;
80 double r[98];
81 double gset;
82 int iset;
83 } awgn_state_t;
84
85 #ifdef __cplusplus
86 extern "C" {
87 #endif
88
89 void awgn_init_dbm0(awgn_state_t *s, int idum, float level);
90
91 void awgn_init_dbov(awgn_state_t *s, int idum, float level);
92
93 int16_t awgn(awgn_state_t *s);
94
95 #ifdef __cplusplus
96 }
97 #endif
98
99 #endif
100 /*- End of file ------------------------------------------------------------*/

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