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- /*
- * aptdec - A lightweight FOSS (NOAA) APT decoder
- * Copyright (C) 2004-2009 Thierry Leconte (F4DWV) 2019-2022 Xerbo (xerbo@protonmail.com)
- *
- * 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 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"
- #include "util.h"
-
- float convolve(const float *in, const float *taps, size_t len) {
- float sum = 0.0;
- for (size_t i = 0; i < len; i++) {
- sum += in[i] * taps[i];
- }
-
- return sum;
- }
-
- complexf_t hilbert_transform(const float *in, const float *taps, size_t len) {
- float i = 0.0;
- float q = 0.0;
-
- for (size_t k = 0; k < len; k++) {
- q += in[2*k] * taps[k];
- i += in[2*k];
- }
-
- i = in[len-1] - (i / len);
- #ifdef _MSC_VER
- return _FCbuild(i, q);
- #else
- return i + q*I;
- #endif
- }
-
- float interpolating_convolve(const float *in, const float *taps, size_t len, float offset, float delta) {
- float out = 0.0;
- float n = offset;
-
- for (size_t i = 0; i < (len-1)/delta-1; n += delta, i++) {
- int k = (int)floor(n);
- float alpha = n - k;
-
- out += in[i] * (taps[k] * (1.0f-alpha) + taps[k + 1] * alpha);
- }
- return out;
- }
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