pareq
Files: pareq.h, pareq.c

Parametric Equalizer This is an implementation of Zoelzer's parametric equalizer filter.

Functions

sp_pareq_create(sp_pareq **pareq)
sp_pareq_init(sp_data *sp, sp_pareq *pareq)
sp_pareq_compute(sp_data *sp, sp_pareq *pareq, SPFLOAT *input, SPFLOAT *out)
sp_pareq_destroy(sp_pareq **pareq)

Optional Parameters

fc: Center frequency in peak mode, corner frequency in shelving mode.
(Default value: 1000)
v: Amount at which the center frequency value shall be increased or decreased. A value of 1 is a flat response.
(Default value: 1)
q: Q of the filter. sqrt(0.5) is no resonance.
(Default value: 0.707)
mode: EQ mode. 0 = peak, 1 = low shelving, 2 = high shelving
(Default value: 0)

Inputs

input: Signal input.

Outputs

out: Signal output.

Example Code

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

typedef struct {
    sp_pareq *pareq;
    sp_noise *noise;
    sp_ftbl *ft; 
} UserData;

void process(sp_data *sp, void *udata) {
    UserData *ud = udata;
    SPFLOAT noise = 0, pareq = 0;
    sp_noise_compute(sp, ud->noise, NULL, &noise);
    sp_pareq_compute(sp, ud->pareq, &noise, &pareq);
    sp->out[0] = pareq;
}

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

    sp_pareq_create(&ud.pareq);
    sp_noise_create(&ud.noise);

    sp_pareq_init(sp, ud.pareq);
    ud.pareq->fc = 500;
    sp_noise_init(sp, ud.noise);
    ud.noise->amp = 0.4;

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

    sp_pareq_destroy(&ud.pareq);
    sp_noise_destroy(&ud.noise);

    sp_destroy(&sp);
    return 0;
}