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49 lines
870 B
C
49 lines
870 B
C
/* Hilbert function */
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/* SPDX-FileCopyrightText: Copyright © 2021 Wim Taymans */
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/* SPDX-License-Identifier: MIT */
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#ifndef HILBERT_H
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#define HILBERT_H
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#ifdef __cplusplus
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extern "C" {
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#endif
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#include <errno.h>
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#include <stddef.h>
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#include <math.h>
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static inline void blackman_window(float *taps, int n_taps)
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{
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int n;
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for (n = 0; n < n_taps; n++) {
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float w = 2 * M_PI * n / (n_taps-1);
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taps[n] = 0.3635819 - 0.4891775 * cos(w)
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+ 0.1365995 * cos(2 * w) - 0.0106411 * cos(3 * w);
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}
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}
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static inline int hilbert_generate(float *taps, int n_taps)
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{
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int i;
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if ((n_taps & 1) == 0)
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return -EINVAL;
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for (i = 0; i < n_taps; i++) {
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int k = -(n_taps / 2) + i;
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if (k & 1) {
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float pk = M_PI * k;
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taps[i] *= (1.0f - cosf(pk)) / pk;
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} else {
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taps[i] = 0.0f;
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}
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}
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return 0;
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}
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#ifdef __cplusplus
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} /* extern "C" */
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#endif
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#endif /* HILBERT_H */
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