From a31630e0d5b9880c716d9004ef4154396ba41ebc Mon Sep 17 00:00:00 2001 From: "Matthias P. Braendli" Date: Thu, 2 Jan 2014 21:55:13 +0100 Subject: Extract fec-3.0.1 --- sim.c | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) create mode 100644 sim.c (limited to 'sim.c') diff --git a/sim.c b/sim.c new file mode 100644 index 0000000..151b04c --- /dev/null +++ b/sim.c @@ -0,0 +1,43 @@ +#include +#include +#include "fec.h" + +#define MAX_RANDOM 0x7fffffff + +/* Generate gaussian random double with specified mean and std_dev */ +double normal_rand(double mean, double std_dev) +{ + double fac,rsq,v1,v2; + static double gset; + static int iset; + + if(iset){ + /* Already got one */ + iset = 0; + return mean + std_dev*gset; + } + /* Generate two evenly distributed numbers between -1 and +1 + * that are inside the unit circle + */ + do { + v1 = 2.0 * (double)random() / MAX_RANDOM - 1; + v2 = 2.0 * (double)random() / MAX_RANDOM - 1; + rsq = v1*v1 + v2*v2; + } while(rsq >= 1.0 || rsq == 0.0); + fac = sqrt(-2.0*log(rsq)/rsq); + gset = v1*fac; + iset++; + return mean + std_dev*v2*fac; +} + +unsigned char addnoise(int sym,double amp,double gain,double offset,int clip){ + int sample; + + sample = offset + gain*normal_rand(sym?amp:-amp,1.0); + /* Clip to 8-bit offset range */ + if(sample < 0) + sample = 0; + else if(sample > clip) + sample = clip; + return sample; +} -- cgit v1.2.3