/*
* 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 .
*/
#include
#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;
}
float complex 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);
return i + q*I;
}
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;
}