jens
843c6e300c
git-svn-id: http://moon:8086/svn/software/trunk/projects/JaySynth@37 b431acfa-c32f-4a4a-93f1-934dc6c82436
95 lines
2.6 KiB
C
95 lines
2.6 KiB
C
// --------------------------------------------------------------
|
||
// --------------------------------------------------------------
|
||
|
||
#include <string.h>
|
||
#include <stdlib.h>
|
||
#include <time.h>
|
||
#include <math.h>
|
||
|
||
#include "synth_defs.h"
|
||
#include "noise.h"
|
||
|
||
// --------------------------------------------------------------
|
||
// internal funcs
|
||
// --------------------------------------------------------------
|
||
#define PM_IA 16807
|
||
#define PM_IM 2147483647
|
||
#define PM_AM (1.0/PM_IM)
|
||
#define PM_IQ 127773
|
||
#define PM_IR 2836
|
||
#define PM_MASK 123459876
|
||
|
||
// 'Minimal' random number generator of Park and Miller. Returns a uniform random deviate
|
||
// between 0.0 and 1.0. Set or resetidumto any integer value (except the unlikely value MASK)
|
||
// to initialize the sequence; idummust not be altered between calls for successive deviates in
|
||
// a sequence.
|
||
double ran0(long *idum)
|
||
{
|
||
long k;
|
||
double ans;
|
||
|
||
*idum ^= PM_MASK; // XORing with MASKallows use of zero and other
|
||
k=(*idum)/PM_IQ; // simple bit patterns for idum.
|
||
*idum=PM_IA*(*idum-k*PM_IQ)-PM_IR *k; // Compute idum=(IA*idum) % IM without over-
|
||
// flows by Schrage’s method.
|
||
if (*idum < 0)
|
||
*idum += PM_IM;
|
||
|
||
ans=PM_AM*(*idum); // Convert idumto a floating result.
|
||
*idum ^= PM_MASK; // Unmask before return.
|
||
|
||
return ans;
|
||
}
|
||
|
||
// --------------------------------------------------------------
|
||
// Exported functions
|
||
// --------------------------------------------------------------
|
||
void Noise_Init(noise_gen_t *pObj, UINT32 seed)
|
||
{
|
||
pObj->state = (long)(seed & NOISE_LFSR_MAX);
|
||
}
|
||
|
||
void Noise_Free(noise_gen_t *pObj)
|
||
{
|
||
}
|
||
|
||
synth_float_t Noise_Uniform(noise_gen_t *pObj, synth_float_t var, synth_float_t mu)
|
||
{
|
||
/*
|
||
if (pObj->lfsr & 0x800000)
|
||
pObj->lfsr = ((pObj->lfsr << 1) | 1) ^ NOISE_LFSR_POLY;
|
||
else
|
||
pObj->lfsr = (pObj->lfsr << 1);
|
||
|
||
pObj->lfsr &= NOISE_LFSR_MAX;
|
||
*/
|
||
|
||
/* taps: 32 31 29 1; characteristic polynomial: x^32 + x^31 + x^29 + x + 1 */
|
||
// pObj->lfsr = (pObj->lfsr >> 1) ^ (-(pObj->lfsr & 1) & NOISE_LFSR_POLY);
|
||
|
||
// return var * ((synth_float_t)rand()/(RAND_MAX+1) + mu -0.5);
|
||
return var*(ran0(&pObj->state) + mu -0.5);
|
||
|
||
}
|
||
|
||
synth_float_t Noise_Gaussian(noise_gen_t *pObj, synth_float_t std, synth_float_t mu)
|
||
{
|
||
synth_float_t U1, U2, V1, V2, S, Y;
|
||
|
||
do
|
||
{
|
||
U1 = Noise_Uniform(pObj, 1, 0.5); // U1=[0,1]
|
||
U2 = Noise_Uniform(pObj, 1, 0.5); // U2=[0,1]
|
||
V1 = 2 * U1 - 1; // V1=[-1,1]
|
||
V2 = 2 * U2 - 1; // V2=[-1,1]
|
||
S = V1 * V1 + V2 * V2;
|
||
|
||
} while (S >= 1);
|
||
|
||
// X = sqrt(-2 * log(S) / S) * V1;
|
||
Y = sqrt(-2 * log(S) / S) * V2;
|
||
Y = mu + std*Y;
|
||
|
||
return Y;
|
||
}
|