oscillators.c

#include <complex.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <tgmath.h>

#define SR 44100
#define SIMPLE_HARMONIC

#ifdef SIMPLE_HARMONIC

int main(void) {
    double freq = 100;
    double phase = 0;

    complex double osc = exp(-I * phase);
    complex double multiplier = exp(-I * 2 * M_PI * freq / SR);

    while (true) {
        fwrite(&osc, sizeof(double), 2, stdout);
        osc *= multiplier;
    }
}

#else

#define TABLE_BITS (16ULL)
#define TABLE_SIZE (1ULL << TABLE_BITS)
#define COUNTER_BITS 32ULL
#define COUNTER_MAX ((1ULL << COUNTER_BITS) - 1ULL)
#define DISCARD_BITS (COUNTER_BITS - TABLE_BITS)
#define DISCARD_MASK ((1ULL << DISCARD_BITS) - 1ULL)

int main(void) {
    double freq = 100;
    double phase = 0;

    double table[TABLE_SIZE];

    for (int i = 0; i < TABLE_SIZE; i++) {
        table[i] = sin(2 * M_PI * i / (double)(TABLE_SIZE));
    }

    uint64_t osc = phase * COUNTER_MAX;
    uint64_t increment = COUNTER_MAX * freq / (double)SR;

    srand48(12345);

    while (true) {
        uint64_t dither[2] = {
            lrand48() & DISCARD_MASK,
            lrand48() & DISCARD_MASK,
        };

        double out[2] = {
            table[((osc + dither[0]) & COUNTER_MAX) >> DISCARD_BITS],
            table[(((osc + dither[1]) + COUNTER_MAX / 4) & COUNTER_MAX) >> DISCARD_BITS],
        };

        fwrite(&out, sizeof(double), 2, stdout);
        osc += increment;
    }
}

#endif