314 lines
10 KiB
C
314 lines
10 KiB
C
/*
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* Brickworks
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*
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* Copyright (C) 2022, 2023 Orastron Srl unipersonale
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*
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* Brickworks 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, version 3 of the License.
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*
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* Brickworks 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 Brickworks. If not, see <http://www.gnu.org/licenses/>.
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*
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* File author: Stefano D'Angelo
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*/
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/*!
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* module_type {{{ dsp }}}
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* version {{{ 1.0.0 }}}
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* requires {{{ bw_common bw_math bw_one_pole }}}
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* description {{{
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* First-order lowpass filter (6 dB/oct) with unitary DC gain.
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*
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* This is better suited to filtering actual audio than
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* [bw_one_pole](bw_one_pole).
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* }}}
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* changelog {{{
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* <ul>
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* <li>Version <strong>1.0.0</strong>:
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* <ul>
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* <li>Now using <code>size_t</code> instead of
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* <code>BW_SIZE_T</code>.</li>
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* </ul>
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* </li>
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* <li>Version <strong>0.6.0</strong>:
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* <ul>
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* <li>Removed dependency on bw_config.</li>
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* </ul>
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* </li>
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* <li>Version <strong>0.5.0</strong>:
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* <ul>
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* <li>Added <code>bw_lp1_process_multi()</code>.</li>
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* <li>Added C++ wrapper.</li>
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* </ul>
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* </li>
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* <li>Version <strong>0.4.0</strong>:
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* <ul>
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* <li>Added initial input value to
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* <code>bw_lp1_reset_state()</code>.</li>
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* <li>Fixed unused parameter warnings.</li>
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* </ul>
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* </li>
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* <li>Version <strong>0.3.0</strong>:
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* <ul>
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* <li>First release.</li>
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* </ul>
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* </li>
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* </ul>
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* }}}
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*/
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#ifndef _BW_LP1_H
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#define _BW_LP1_H
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#include <bw_common.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/*! api {{{
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* #### bw_lp1_coeffs
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* ```>>> */
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typedef struct _bw_lp1_coeffs bw_lp1_coeffs;
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/*! <<<```
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* Coefficients and related.
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*
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* #### bw_lp1_state
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* ```>>> */
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typedef struct _bw_lp1_state bw_lp1_state;
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/*! <<<```
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* Internal state and related.
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*
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* #### bw_lp1_init()
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* ```>>> */
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static inline void bw_lp1_init(bw_lp1_coeffs *BW_RESTRICT coeffs);
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/*! <<<```
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* Initializes input parameter values in `coeffs`.
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*
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* #### bw_lp1_set_sample_rate()
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* ```>>> */
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static inline void bw_lp1_set_sample_rate(bw_lp1_coeffs *BW_RESTRICT coeffs, float sample_rate);
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/*! <<<```
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* Sets the `sample_rate` (Hz) value in `coeffs`.
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*
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* #### bw_lp1_reset_coeffs()
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* ```>>> */
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static inline void bw_lp1_reset_coeffs(bw_lp1_coeffs *BW_RESTRICT coeffs);
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/*! <<<```
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* Resets coefficients in `coeffs` to assume their target values.
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*
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* #### bw_lp1_reset_state()
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* ```>>> */
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static inline void bw_lp1_reset_state(const bw_lp1_coeffs *BW_RESTRICT coeffs, bw_lp1_state *BW_RESTRICT state, float x0);
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/*! <<<```
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* Resets the given `state` to its initial values using the given `coeffs`
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* and the quiescent/initial input value `x0`.
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*
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* #### bw_lp1_update_coeffs_ctrl()
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* ```>>> */
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static inline void bw_lp1_update_coeffs_ctrl(bw_lp1_coeffs *BW_RESTRICT coeffs);
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/*! <<<```
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* Triggers control-rate update of coefficients in `coeffs`.
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*
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* #### bw_lp1_update_coeffs_audio()
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* ```>>> */
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static inline void bw_lp1_update_coeffs_audio(bw_lp1_coeffs *BW_RESTRICT coeffs);
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/*! <<<```
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* Triggers audio-rate update of coefficients in `coeffs`.
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*
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* #### bw_lp1_process1()
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* ```>>> */
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static inline float bw_lp1_process1(const bw_lp1_coeffs *BW_RESTRICT coeffs, bw_lp1_state *BW_RESTRICT state, float x);
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/*! <<<```
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* Processes one input sample `x` using `coeffs`, while using and updating
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* `state`. Returns the corresponding output sample.
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*
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* #### bw_lp1_process()
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* ```>>> */
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static inline void bw_lp1_process(bw_lp1_coeffs *BW_RESTRICT coeffs, bw_lp1_state *BW_RESTRICT state, const float *x, float *y, int n_samples);
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/*! <<<```
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* Processes the first `n_samples` of the input buffer `x` and fills the
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* first `n_samples` of the output buffer `y`, while using and updating both
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* `coeffs` and `state` (control and audio rate).
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*
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* #### bw_lp1_process_multi()
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* ```>>> */
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static inline void bw_lp1_process_multi(bw_lp1_coeffs *BW_RESTRICT coeffs, bw_lp1_state **BW_RESTRICT state, const float **x, float **y, int n_channels, int n_samples);
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/*! <<<```
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* Processes the first `n_samples` of the `n_channels` input buffers `x` and
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* fills the first `n_samples` of the `n_channels` output buffers `y`, while
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* using and updating both the common `coeffs` and each of the `n_channels`
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* `state`s (control and audio rate).
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*
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* #### bw_lp1_set_cutoff()
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* ```>>> */
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static inline void bw_lp1_set_cutoff(bw_lp1_coeffs *BW_RESTRICT coeffs, float value);
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/*! <<<```
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* Sets the cutoff frequency `value` (Hz) in `coeffs`.
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*
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* Default value: `1e3f`.
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*
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* #### bw_lp1_set_prewarp_at_cutoff()
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* ```>>> */
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static inline void bw_lp1_set_prewarp_at_cutoff(bw_lp1_coeffs *BW_RESTRICT coeffs, char value);
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/*! <<<```
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* Sets whether bilinear transform prewarping frequency should match the
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* cutoff frequency (non-`0`) or not (`0`).
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*
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* Default value: non-`0` (on).
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*
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* #### bw_lp1_set_prewarp_freq()
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* ```>>> */
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static inline void bw_lp1_set_prewarp_freq(bw_lp1_coeffs *BW_RESTRICT coeffs, float value);
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/*! <<<```
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* Sets the prewarping frequency `value` (Hz) in `coeffs`.
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*
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* Only used when the prewarp\_at\_cutoff parameter is off.
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*
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* Default value: `1e3f`.
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* }}} */
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#ifdef __cplusplus
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}
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#endif
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/*** Implementation ***/
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/* WARNING: This part of the file is not part of the public API. Its content may
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* change at any time in future versions. Please, do not use it directly. */
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#include <bw_math.h>
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#include <bw_one_pole.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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struct _bw_lp1_coeffs {
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// Sub-components
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bw_one_pole_coeffs smooth_coeffs;
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bw_one_pole_state smooth_cutoff_state;
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bw_one_pole_state smooth_prewarp_freq_state;
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// Coefficients
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float t_k;
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float prewarp_k;
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float t;
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float X_x;
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float X_X_z1;
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float y_X;
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// Parameters
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float cutoff;
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float prewarp_freq;
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};
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struct _bw_lp1_state {
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float y_z1;
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float X_z1;
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};
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static inline void bw_lp1_init(bw_lp1_coeffs *BW_RESTRICT coeffs) {
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bw_one_pole_init(&coeffs->smooth_coeffs);
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bw_one_pole_set_tau(&coeffs->smooth_coeffs, 0.005f);
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bw_one_pole_set_sticky_thresh(&coeffs->smooth_coeffs, 1e-3f);
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coeffs->cutoff = 1e3f;
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coeffs->prewarp_freq = 1e3f;
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coeffs->prewarp_k = 1.f;
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}
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static inline void bw_lp1_set_sample_rate(bw_lp1_coeffs *BW_RESTRICT coeffs, float sample_rate) {
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bw_one_pole_set_sample_rate(&coeffs->smooth_coeffs, sample_rate);
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bw_one_pole_reset_coeffs(&coeffs->smooth_coeffs);
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coeffs->t_k = 3.141592653589793f / sample_rate;
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}
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static inline void _bw_lp1_do_update_coeffs(bw_lp1_coeffs *BW_RESTRICT coeffs, char force) {
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const float prewarp_freq = coeffs->prewarp_freq + coeffs->prewarp_k * (coeffs->cutoff - coeffs->prewarp_freq);
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float prewarp_freq_cur = bw_one_pole_get_y_z1(&coeffs->smooth_prewarp_freq_state);
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float cutoff_cur = bw_one_pole_get_y_z1(&coeffs->smooth_cutoff_state);
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const char prewarp_freq_changed = force || prewarp_freq != prewarp_freq_cur;
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const char cutoff_changed = force || coeffs->cutoff != cutoff_cur;
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if (prewarp_freq_changed || cutoff_changed) {
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if (prewarp_freq_changed) {
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prewarp_freq_cur = bw_one_pole_process1_sticky_rel(&coeffs->smooth_coeffs, &coeffs->smooth_prewarp_freq_state, prewarp_freq);
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coeffs->t = bw_tanf(coeffs->t_k * prewarp_freq_cur);
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}
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if (cutoff_changed) {
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cutoff_cur = bw_one_pole_process1_sticky_rel(&coeffs->smooth_coeffs, &coeffs->smooth_cutoff_state, coeffs->cutoff);
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coeffs->y_X = bw_rcpf(cutoff_cur);
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}
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const float k = cutoff_cur * bw_rcpf(cutoff_cur * coeffs->t + prewarp_freq_cur);
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coeffs->X_x = k * prewarp_freq_cur;
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coeffs->X_X_z1 = k * coeffs->t;
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}
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}
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static inline void bw_lp1_reset_coeffs(bw_lp1_coeffs *BW_RESTRICT coeffs) {
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bw_one_pole_reset_state(&coeffs->smooth_coeffs, &coeffs->smooth_cutoff_state, coeffs->cutoff);
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bw_one_pole_reset_state(&coeffs->smooth_coeffs, &coeffs->smooth_prewarp_freq_state, coeffs->prewarp_freq + coeffs->prewarp_k * (coeffs->cutoff - coeffs->prewarp_freq));
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_bw_lp1_do_update_coeffs(coeffs, 1);
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}
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static inline void bw_lp1_reset_state(const bw_lp1_coeffs *BW_RESTRICT coeffs, bw_lp1_state *BW_RESTRICT state, float x0) {
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(void)coeffs;
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state->y_z1 = x0;
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state->X_z1 = 0.f;
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}
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static inline void bw_lp1_update_coeffs_ctrl(bw_lp1_coeffs *BW_RESTRICT coeffs) {
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(void)coeffs;
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}
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static inline void bw_lp1_update_coeffs_audio(bw_lp1_coeffs *BW_RESTRICT coeffs) {
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_bw_lp1_do_update_coeffs(coeffs, 0);
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}
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static inline float bw_lp1_process1(const bw_lp1_coeffs *BW_RESTRICT coeffs, bw_lp1_state *BW_RESTRICT state, float x) {
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const float X = coeffs->X_x * (x - state->y_z1) - coeffs->X_X_z1 * state->X_z1;
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const float y = x - coeffs->y_X * X;
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state->y_z1 = y;
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state->X_z1 = X;
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return y;
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}
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static inline void bw_lp1_process(bw_lp1_coeffs *BW_RESTRICT coeffs, bw_lp1_state *BW_RESTRICT state, const float *x, float *y, int n_samples) {
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for (int i = 0; i < n_samples; i++) {
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bw_lp1_update_coeffs_audio(coeffs);
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y[i] = bw_lp1_process1(coeffs, state, x[i]);
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}
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}
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static inline void bw_lp1_process_multi(bw_lp1_coeffs *BW_RESTRICT coeffs, bw_lp1_state **BW_RESTRICT state, const float **x, float **y, int n_channels, int n_samples) {
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for (int i = 0; i < n_samples; i++) {
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bw_lp1_update_coeffs_audio(coeffs);
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for (int j = 0; j < n_channels; j++)
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y[j][i] = bw_lp1_process1(coeffs, state[j], x[j][i]);
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}
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}
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static inline void bw_lp1_set_cutoff(bw_lp1_coeffs *BW_RESTRICT coeffs, float value) {
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coeffs->cutoff = value;
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}
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static inline void bw_lp1_set_prewarp_at_cutoff(bw_lp1_coeffs *BW_RESTRICT coeffs, char value) {
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coeffs->prewarp_k = value ? 1.f : 0.f;
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}
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static inline void bw_lp1_set_prewarp_freq(bw_lp1_coeffs *BW_RESTRICT coeffs, float value) {
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coeffs->prewarp_freq = value;
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}
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#ifdef __cplusplus
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}
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#endif
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#endif
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