ref: 9b8757eabebe9ae91d613d3c6a6ce5f00fd766ed
dir: /src/mask.c/
/*
* July 5, 1991
* Copyright 1991 Lance Norskog And Sundry Contributors
* This source code is freely redistributable and may be used for
* any purpose. This copyright notice must be maintained.
* Lance Norskog And Sundry Contributors are not responsible for
* the consequences of using this software.
*/
/*
* Sound Tools masking noise effect file.
*/
#include <stdlib.h>
#include <math.h>
#include "st.h"
#include "libst.h"
#define HALFABIT 1.44 /* square root of 2 */
/*
* Problems:
* 1) doesn't allow specification of noise depth
* 2) does triangular noise, could do local shaping
* 3) can run over 32 bits.
*/
/*
* Process options
*/
void mask_getopts(effp, n, argv)
eff_t effp;
int n;
char **argv;
{
if (n)
fail("Mask effect takes no options.");
/* should take # of bits */
st_initrand();
}
/*
* Processed signed long samples from ibuf to obuf.
* Return number of samples processed.
*/
void mask_flow(effp, ibuf, obuf, isamp, osamp)
eff_t effp;
LONG *ibuf, *obuf;
int *isamp, *osamp;
{
int len, done;
LONG l;
LONG tri16; /* 16 signed bits of triangular noise */
len = ((*isamp > *osamp) ? *osamp : *isamp);
switch (effp->outinfo.style) {
case ULAW:
case ALAW:
for(done = 0; done < len; done++) {
tri16 = (rand() + rand()) - 32767;
l = *ibuf++ + tri16*16*HALFABIT; /* 2^4.5 */
*obuf++ = l;
}
break;
default:
switch (effp->outinfo.size) {
case BYTE:
for(done = 0; done < len; done++) {
tri16 = (rand() + rand()) - 32767;
l = *ibuf++ + tri16*256*HALFABIT; /* 2^8.5 */
*obuf++ = l;
}
break;
case WORD:
for(done = 0; done < len; done++) {
tri16 = (rand() + rand()) - 32767;
l = *ibuf++ + tri16*HALFABIT; /* 2^.5 */
*obuf++ = l;
}
break;
default:
for(done = 0; done < len; done++) {
*obuf++ = *ibuf++;
}
break;
}
}
*isamp = done;
*osamp = done;
}