72 lines
2.4 KiB
C
72 lines
2.4 KiB
C
/**
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* Copyright 2022 Colin Lam, Ploopy Corporation
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*
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* This program 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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* This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
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*
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* SPECIAL THANKS TO:
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* Robert Bristow-Johnson, a.k.a. RBJ
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* for his exceptional work on biquad formulae as applied to digital
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* audio filtering, summarised in his pamphlet, "Audio EQ Cookbook".
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*/
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#ifndef BQF_H
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#define BQF_H
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#include "fix16.h"
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typedef struct _bqf_coeff_t {
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fix3_28_t a0;
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fix3_28_t a1;
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fix3_28_t a2;
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fix3_28_t b0;
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fix3_28_t b1;
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fix3_28_t b2;
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} bqf_coeff_t;
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typedef struct _bqf_mem_t {
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fix3_28_t x_1;
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fix3_28_t x_2;
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fix3_28_t y_1;
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fix3_28_t y_2;
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} bqf_mem_t;
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// In reality we do not have enough CPU resource to run 8 filtering
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// stages without some optimisation.
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#define MAX_FILTER_STAGES 8
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extern int filter_stages;
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extern bqf_coeff_t bqf_filters_left[MAX_FILTER_STAGES];
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extern bqf_coeff_t bqf_filters_right[MAX_FILTER_STAGES];
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extern bqf_mem_t bqf_filters_mem_left[MAX_FILTER_STAGES];
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extern bqf_mem_t bqf_filters_mem_right[MAX_FILTER_STAGES];
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#define Q_BUTTERWORTH 0.707106781
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#define Q_BESSEL 0.577350269
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#define Q_LINKWITZ_RILEY 0.5
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void bqf_lowpass_config(double, double, double, bqf_coeff_t *);
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void bqf_highpass_config(double, double, double, bqf_coeff_t *);
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void bqf_bandpass_skirt_config(double, double, double, bqf_coeff_t *);
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void bqf_bandpass_peak_config(double, double, double, bqf_coeff_t *);
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void bqf_notch_config(double, double, double, bqf_coeff_t *);
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void bqf_allpass_config(double, double, double, bqf_coeff_t *);
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void bqf_peaking_config(double, double, double, double, bqf_coeff_t *);
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void bqf_lowshelf_config(double, double, double, double, bqf_coeff_t *);
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void bqf_highshelf_config(double, double, double, double, bqf_coeff_t *);
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fix3_28_t bqf_transform(fix3_28_t, bqf_coeff_t *, bqf_mem_t *);
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void bqf_memreset(bqf_mem_t *);
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#endif
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