/* * SpanDSP - a series of DSP components for telephony * * awgn.h - An additive Gaussian white noise generator * * Written by Steve Underwood <steveu@coppice.org> * * Copyright (C) 2001 Steve Underwood * * All rights reserved. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2, as * published by the Free Software Foundation. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. * * $Id: awgn.h,v 1.11 2007/04/08 08:16:17 steveu Exp $ *//*! \file *//* This code is based on some demonstration code in a research   paper somewhere. I can't track down where I got the original from,   so that due recognition can be given. The original had no explicit   copyright notice, and I hope nobody objects to its use here.      Having a reasonable Gaussian noise generator is pretty important for   telephony testing (in fact, pretty much any DSP testing), and this   one seems to have served me OK. Since the generation of Gaussian   noise is only for test purposes, and not a core system component,   I don't intend to worry excessively about copyright issues, unless   someone worries me.           The non-core nature of this code also explains why it is unlikely   to ever be optimised. */#if !defined(_SPANDSP_AWGN_H_)#define _SPANDSP_AWGN_H_/*! \page awgn_page Additive white gaussian noise (AWGN) generation\section awgn_page_sec_1 What does it do?Adding noise is not the most useful thing in most DSP applications, but it isawfully useful for test suites. \section awgn_page_sec_2 How does it work?This code is based on some demonstration code in a research paper somewhere. Ican't track down where I got the original from, so that due recognition can begiven. The original had no explicit copyright notice, and I hope nobody objectsto its use here. Having a reasonable Gaussian noise generator is pretty important for telephonytesting (in fact, pretty much any DSP testing), and this one seems to haveserved me OK. Since the generation of Gaussian noise is only for test purposes,and not a core system component, I don't intend to worry excessively aboutcopyright issues, unless someone worries me. The non-core nature of this code also explains why it is unlikely to ever beoptimised.*//*!    AWGN generator descriptor. This contains all the state information for an AWGN generator. */typedef struct{    double rms;    long int ix1;    long int ix2;    long int ix3;    double r[98];    double gset;    int iset;} awgn_state_t;#if defined(__cplusplus)extern "C"{#endifvoid awgn_init_dbm0(awgn_state_t *s, int idum, float level);void awgn_init_dbov(awgn_state_t *s, int idum, float level);int16_t awgn(awgn_state_t *s);#if defined(__cplusplus)}#endif#endif/*- End of file ------------------------------------------------------------*/