|
- /*
- * This file is part of Aptdec.
- * Copyright (c) 2004-2009 Thierry Leconte (F4DWV), Xerbo (xerbo@protonmail.com) 2019-2020
- *
- * Aptdec 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 2 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 <https://www.gnu.org/licenses/>.
- *
- */
-
- #include <math.h>
-
- #include "filter.h"
-
- // Finite impulse response
- float fir(float *buff, const float *coeff, const int len) {
- double r;
-
- r = 0.0;
- for (int i = 0; i < len; i++) {
- r += buff[i] * coeff[i];
- }
- return r;
- }
-
- /* IQ finite impulse response
- * Turn samples into a single IQ sample
- */
- void iqfir(float *buff, const float *coeff, const int len, double *I, double *Q) {
- double i = 0.0, q = 0.0;
-
- for (int k = 0; k < len; k++) {
- q += buff[2*k] * coeff[k];
- i += buff[2*k];
- }
-
- i = buff[len-1] - (i / len);
- *I = i, *Q = q;
- }
-
- /* Gaussian finite impulse responce compensation
- * https://www.recordingblogs.com/wiki/gaussian-window
- */
- float rsfir(double *buff, const float *coeff, const int len, const double offset, const double delta) {
- double out;
-
- out = 0.0;
- double n = offset;
- for (int i = 0; i < (len-1)/delta-1; n += delta, i++) {
- int k;
- double alpha;
-
- k = (int)floor(n);
- alpha = n - k;
- out += buff[i] * (coeff[k] * (1.0 - alpha) + coeff[k + 1] * alpha);
- }
- return out;
- }
|