**diff options**

Diffstat (limited to 'src/common/filter.c')

-rw-r--r-- | src/common/filter.c | 99 |

1 files changed, 0 insertions, 99 deletions

diff --git a/src/common/filter.c b/src/common/filter.c deleted file mode 100644 index 0a5c0dd..0000000 --- a/src/common/filter.c +++ /dev/null @@ -1,99 +0,0 @@ -/* cut-off filter (biquad) based on Nigel Redmon (www.earlevel.com) - * - * (C) 2016 by Andreas Eversberg <jolly@eversberg.eu> - * All Rights Reserved - * - * This program is free software: you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation, either version 3 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program. If not, see <http://www.gnu.org/licenses/>. - */ - -#include <stdio.h> -#include <stdint.h> -#include <string.h> -#include <stdlib.h> -#include <math.h> -#include "sample.h" -#include "filter.h" - -#define PI M_PI - -void filter_lowpass_init(filter_t *bq, double frequency, int samplerate, int iterations) -{ - double Fc, Q, K, norm; - - if (iterations > 64) { - fprintf(stderr, "%s failed: too many iterations, please fix!\n", __func__); - abort(); - } - - memset(bq, 0, sizeof(*bq)); - bq->iter = iterations; - Q = pow(sqrt(0.5), 1.0 / (double)iterations); /* 0.7071 @ 1 iteration */ - Fc = frequency / (double)samplerate; - K = tan(PI * Fc); - norm = 1 / (1 + K / Q + K * K); - bq->a0 = K * K * norm; - bq->a1 = 2 * bq->a0; - bq->a2 = bq->a0; - bq->b1 = 2 * (K * K - 1) * norm; - bq->b2 = (1 - K / Q + K * K) * norm; -} - -void filter_highpass_init(filter_t *bq, double frequency, int samplerate, int iterations) -{ - double Fc, Q, K, norm; - - memset(bq, 0, sizeof(*bq)); - bq->iter = iterations; - Q = pow(sqrt(0.5), 1.0 / (double)iterations); /* 0.7071 @ 1 iteration */ - Fc = frequency / (double)samplerate; - K = tan(PI * Fc); - norm = 1 / (1 + K / Q + K * K); - bq->a0 = 1 * norm; - bq->a1 = -2 * bq->a0; - bq->a2 = bq->a0; - bq->b1 = 2 * (K * K - 1) * norm; - bq->b2 = (1 - K / Q + K * K) * norm; -} - -void filter_process(filter_t *bq, sample_t *samples, int length) -{ - double a0, a1, a2, b1, b2; - double *z1, *z2; - double in, out; - int iterations = bq->iter; - int i, j; - - /* get states */ - a0 = bq->a0; - a1 = bq->a1; - a2 = bq->a2; - b1 = bq->b1; - b2 = bq->b2; - - z1 = bq->z1; - z2 = bq->z2; - - /* process filter */ - for (i = 0; i < length; i++) { - in = *samples; - for (j = 0; j < iterations; j++) { - out = in * a0 + z1[j]; - z1[j] = in * a1 + z2[j] - b1 * out; - z2[j] = in * a2 - b2 * out; - in = out; - } - *samples++ = in; - } -} - |