ref: 03961e94972a0419db48886a1067158d9ca3d85b
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_i.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 */ int st_mask_getopts(eff_t effp, int n, char **argv) { if (n) { st_fail("Mask effect takes no options."); return (ST_EOF); } /* should take # of bits */ st_initrand(); return (ST_SUCCESS); } /* * Processed signed long samples from ibuf to obuf. * Return number of samples processed. */ int st_mask_flow(eff_t effp, st_sample_t *ibuf, st_sample_t *obuf, st_size_t *isamp, st_size_t *osamp) { int len, done; st_sample_t l; st_sample_t tri16; /* 16 signed bits of triangular noise */ len = ((*isamp > *osamp) ? *osamp : *isamp); switch (effp->outinfo.encoding) { case ST_ENCODING_ULAW: case ST_ENCODING_ALAW: for(done = 0; done < len; done++) { tri16 = ((rand()%32768L) + (rand()%32768L)) - 32767; l = *ibuf++ + tri16*16*HALFABIT; /* 2^4.5 */ *obuf++ = l; } break; default: switch (effp->outinfo.size) { case ST_SIZE_BYTE: for(done = 0; done < len; done++) { tri16 = ((rand()%32768L) + (rand()%32768L)) - 32767; l = *ibuf++ + tri16*256*HALFABIT; /* 2^8.5 */ *obuf++ = l; } break; case ST_SIZE_WORD: for(done = 0; done < len; done++) { tri16 = ((rand()%32768L) + (rand()%32768L)) - 32767; l = *ibuf++ + tri16*HALFABIT; /* 2^.5 */ *obuf++ = l; } break; default: for(done = 0; done < len; done++) { *obuf++ = *ibuf++; } break; } } *isamp = done; *osamp = done; return (ST_SUCCESS); }