pdhalf

Casio-style phase distortion with "pivot point" on the X axis This module is designed to emulate the classic phase distortion synthesis technique. From the mid 90's. The technique reads the first and second halves of the ftbl at different rates in order to warp the waveform. For example, pdhalf can smoothly transition a sinewave into something approximating a sawtooth wave.

#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include "soundpipe.h"

typedef struct {
    sp_metro *met;
    sp_ftbl *ft; 
    sp_tabread *tab;
    sp_phasor *phs;
    sp_tenv *tenv;
    sp_pdhalf *pdhalf;
    sp_scale *scl;
    sp_tseq *ts;
    sp_ftbl *seq; 
} UserData;

void process(sp_data *sp, void *udata) 
{
    UserData *ud = udata;
    SPFLOAT met = 0;
    SPFLOAT tenv = 0;
    SPFLOAT phs = 0;
    SPFLOAT pd = 0;
    SPFLOAT tr = 0;
    SPFLOAT amt = 0;
    SPFLOAT rev = 0;
    SPFLOAT frq = 0;

    sp_metro_compute(sp, ud->met, NULL, &met);
    sp_tenv_compute(sp, ud->tenv, &met, &tenv);
    sp_tseq_compute(sp, ud->ts, &met, &frq);
    frq = sp_midi2cps(frq);
    ud->phs->freq = frq;
    sp_phasor_compute(sp, ud->phs, NULL, &phs);
    rev = 1 - tenv;
    sp_scale_compute(sp, ud->scl, &rev, &amt);
    ud->pdhalf->amount = amt;
    sp_pdhalf_compute(sp, ud->pdhalf, &phs, &pd);
    ud->tab->index = pd;
    sp_tabread_compute(sp, ud->tab, NULL, &tr);

    sp_out(sp, 0, tr * tenv);

}

int main() 
{
    UserData ud;
    sp_data *sp;
    sp_create(&sp);
    sp_srand(sp, 1234567);

    sp_pdhalf_create(&ud.pdhalf);
    sp_ftbl_create(sp, &ud.ft, 2048);
    sp_gen_sine(sp, ud.ft);
    sp_metro_create(&ud.met);

    sp_tabread_create(&ud.tab);
    sp_tenv_create(&ud.tenv);
    sp_phasor_create(&ud.phs);
    sp_scale_create(&ud.scl);
    sp_ftbl_create(sp, &ud.seq, 1);
    sp_gen_vals(sp, ud.seq, "62 67 69 72");
    sp_tseq_create(&ud.ts);


    sp_pdhalf_init(sp, ud.pdhalf);
    sp_tabread_init(sp, ud.tab, ud.ft, 1);
    sp_phasor_init(sp, ud.phs, 0);
    ud.phs->freq = 440;
    sp_tenv_init(sp, ud.tenv);
    ud.tenv->atk = 0.001;
    ud.tenv->hold = 0.01;
    ud.tenv->rel = 0.2;
    sp_metro_init(sp, ud.met);
    ud.met->freq = 8;
    sp_scale_init(sp, ud.scl);
    ud.scl->min = -0.8;
    ud.scl->max = 0;
    sp_tseq_init(sp, ud.ts, ud.seq);


    sp->len = 44100 * 5;
    sp_process(sp, &ud, process);

    sp_pdhalf_destroy(&ud.pdhalf);
    sp_ftbl_destroy(&ud.ft);
    sp_tabread_destroy(&ud.tab);
    sp_phasor_destroy(&ud.phs);
    sp_tenv_destroy(&ud.tenv);
    sp_metro_destroy(&ud.met);
    sp_scale_destroy(&ud.scl);
    sp_tseq_destroy(&ud.ts);
    sp_ftbl_destroy(&ud.seq);

    sp_destroy(&sp);
    return 0;
}