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60 lines
1.7 KiB
C
60 lines
1.7 KiB
C
/* spek-fft.c
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*
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* Copyright (C) 2010 Alexander Kojevnikov <alexander@kojevnikov.com>
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*
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* Spek is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Spek is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Spek. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <math.h>
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#include <libavutil/mem.h>
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#include "spek-fft.h"
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SpekFftPlan * spek_fft_plan_new (gint n, gint threshold) {
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gint bits;
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SpekFftPlan *p = g_new0 (SpekFftPlan, 1);
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p->input = av_mallocz (sizeof (gfloat) * n);
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p->output = av_mallocz (sizeof (gfloat) * (n / 2 + 1));
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p->threshold = threshold;
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for (bits = 0; n; n >>= 1, bits++);
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p->n = 1 << --bits;
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p->cx = av_rdft_init (bits, DFT_R2C);
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return p;
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}
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void spek_fft_execute (SpekFftPlan *p) {
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int i;
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int n = p->n;
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av_rdft_calc (p->cx, p->input);
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/* Calculate magnitudes */
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p->output[0] = p->input[0] * p->input[0] / (n * n);
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p->output[n / 2] = p->input[1] * p->input[1] / (n * n);
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for (i = 1; i < n / 2; i++) {
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gfloat val;
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val = p->input[i * 2] * p->input[i * 2] + p->input[i * 2 + 1] * p->input[i * 2 + 1];
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val /= n * n;
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val = 10.0 * log10f (val);
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p->output[i] = val < p->threshold ? p->threshold : val;
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}
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}
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void spek_fft_destroy (SpekFftPlan *p) {
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av_rdft_end (p->cx);
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av_free (p->input);
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av_free (p->output);
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g_free (p);
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}
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