fosc
Files: fosc.h, fosc.c

FM oscilator pair with linear interpolation

Functions

sp_fosc_create(sp_fosc **fosc)
sp_fosc_init(sp_data *sp, sp_fosc *fosc, sp_ftbl *tbl)
sp_fosc_compute(sp_data *sp, sp_fosc *fosc, SPFLOAT *dummy, SPFLOAT *out)
sp_fosc_destroy(sp_fosc **fosc)

Mandatory Parameters

tbl: Wavetable to read from. Note: the size of this table must be a power of 2.
(Recommended value: N/A)

Optional Parameters

freq: Frequency (in Hz)
(Default value: 440)
amp: Amplitude (typically a value between 0 and 1).
(Default value: 0.4)
car: Carrier frequency, expressed as a ratio number in C:M ratio. Typically an integer.
(Default value: 1)
mod: Modulator frequency, expressed as a ratio number in C:M ratio. Typically an integer.
(Default value: 1)
indx: Modulation index. Most commercial synthesizers have a range from 0-8, but there's nothing stopping you from going beyond that.
(Default value: 8)

Outputs

out: Signal out.

Example Code

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

typedef struct {
    sp_fosc *osc;
    sp_ftbl *ft; 
    int counter;
} UserData;

void process(sp_data *sp, void *udata) {
    UserData *ud = ud;
    if(ud->counter == 0){
        ud->osc->freq = 500 + rand() % 2000;
    }
    sp_fosc_compute(sp, ud->osc, NULL, &sp->out[0]);
    ud->counter = (ud->counter + 1) % 4410;
}

int main() {
    srand(time(NULL));
    UserData ud;
    ud.counter = 0;
    sp_data *sp;
    sp_create(&sp);
    sp_ftbl_create(sp, &ud.ft, 2048);
    sp_fosc_create(&ud.osc);

    sp_gen_sine(sp, ud.ft);
    sp_fosc_init(sp, ud.osc, ud.ft);
    ud.osc->freq = 500;
    sp->len = 44100 * 5;
    sp_process(sp, &ud, process);

    sp_ftbl_destroy(&ud.ft);
    sp_fosc_destroy(&ud.osc);
    sp_destroy(&sp);
    return 0;
}