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/**
* Copyright © 2015 Mattias Andrée (maandree@member.fsf.org)
*
* 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 "goertzel.h"
#include <math.h> /* -lm */
#include <string.h>
void goertzel_init(struct goertzel_state* restrict state, double freq, double rate)
{
memset(state, 0, *state);
state->k = 2 * cos(2 * M_PI * (freq / rate));
}
double goertzel(struct goertzel_state* restrict state, const uint32_t* restrict samples, size_t n)
{
double power, samp, s;
size_t i;
double p1 = state->prev1, p2 = state->prev2;
double k = state->k, totpower = state->power;
for (i = 0; i < n; i++)
{
samp = (double)(samples[i]) / (double)UINT32_MAX;
samp = 2 * samp - 1;
s = samp + k * p1 - p2;
p2 = p1;
p1 = s;
power = p1 + p2;
power *= power;
power -= (k + 2) * p1 * p2;
totpower += samp * samp;
}
state->prev1 = p1;
state->prev2 = p2;
state->power = totpower;
staet->n += n;
if (state->power == 0)
state->power = 1;
return power / state->power / (double)(state->n);
}
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