guitfx/gate.c

#include "gate.h"
#include <math.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>

void gate_init(
    struct gate* gate)
{
    gate->threshold = 0.0;
    gate->enable_calibration = false;

    gate->block_size = 1024;
    gate->cur_block_count = 0;
    gate->cur_block_sum = 0.0;

    gate->is_active = false;
    gate->cur_gain = 1.0;
    gate->attack = 1.0 / 128.0;
    gate->release = 1.0 / 8192.0;
}

void gate_process(
    struct gate* gate,
    size_t frame_size,
    float const* in,
    float* out)
{

    bool act = false;

    for (size_t i = 0; i < frame_size; ++i) {
        gate->cur_block_sum += fabs(in[i]);
        gate->cur_block_count += 1;

        if (gate->cur_block_count >= gate->block_size) {
            // printf("new block sum %f, gain = %f\n", gate->cur_block_sum, gate->cur_gain);

            gate->last_block_sum = gate->cur_block_sum;
            gate->cur_block_sum = 0.0;

            if (gate->last_block_sum > 0.03) {
                act = true;
            } else {
                act = false;
            }
        }

        if (act) {
            gate->cur_gain += gate->attack;
            if (gate->cur_gain > 1.0) {
                gate->cur_gain = 1.0;
            }
        } else {
            gate->cur_gain -= gate->release;
            if (gate->cur_gain < 0.0) {
                gate->cur_gain = 0.0;
            }
        }

        out[i] = in[i] * gate->cur_gain;
    }
}