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/* spek-fft.c
*
* Copyright (C) 2010-2012 Alexander Kojevnikov <alexander@kojevnikov.com>
*
* Spek 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.
*
* Spek 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 Spek. If not, see <http://www.gnu.org/licenses/>.
*/
#include <math.h>
#include <libavcodec/avfft.h>
#include <libavutil/mem.h>
#include "spek-fft.h"
struct spek_fft_plan * spek_fft_plan_new(int n)
{
struct spek_fft_plan *p = malloc(sizeof(struct spek_fft_plan));
p->input = av_mallocz(sizeof(float) * n);
p->output = av_mallocz(sizeof(float) * (n / 2 + 1));
int bits = 0;
while (n) {
n >>= 1;
++bits;
}
p->n = 1 << --bits;
p->cx = av_rdft_init(bits, DFT_R2C);
return p;
}
void spek_fft_execute(struct spek_fft_plan *p)
{
av_rdft_calc(p->cx, p->input);
// Calculate magnitudes.
int n = p->n;
p->output[0] = p->input[0] * p->input[0] / (n * n);
p->output[n / 2] = p->input[1] * p->input[1] / (n * n);
for (int i = 1; i < n / 2; i++) {
float val =
p->input[i * 2] * p->input[i * 2] +
p->input[i * 2 + 1] * p->input[i * 2 + 1];
val /= n * n;
p->output[i] = 10.0 * log10f (val);
}
}
void spek_fft_delete(struct spek_fft_plan *p)
{
av_rdft_end(p->cx);
av_free(p->input);
av_free(p->output);
free(p);
}
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