280 lines
9.1 KiB
C
280 lines
9.1 KiB
C
/*
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* Brickworks
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*
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* Copyright (C) 2022 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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*
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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 {{{ 0.2.0 }}}
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* requires {{{ bw_config bw_common bw_one_pole bw_math }}}
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* description {{{
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* Antialiased tanh-based saturation with parametric bias and gain
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* (compensation) and output bias removal.
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*
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* In other words this implements
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*
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* > y(n) = tanh(gain \* x(n) + bias) - tanh(bias)
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*
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* with antialiasing and optionally dividing the output by gain.
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*
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* As a side effect, antialiasing causes attenuation at higher frequencies
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* (about 3 dB at 0.5 × Nyquist frequency and rapidly increasing at higher
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* frequencies).
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* }}}
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* changelog {{{
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* <ul>
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* <li>Version <strong>0.2.0</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_SATUR_H
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#define _BW_SATUR_H
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#ifdef __cplusplus
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extern "C" {
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#endif
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#include <bw_common.h>
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/*! api {{{
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* #### bw_satur_coeffs
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* ```>>> */
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typedef struct _bw_satur_coeffs bw_satur_coeffs;
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/*! <<<```
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* Coefficients and related.
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*
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* ### bw_satur_state
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* ```>>> */
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typedef struct _bw_satur_state bw_satur_state;
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/*! <<<```
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* Internal state and related.
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*
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* #### bw_satur_init()
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* ```>>> */
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static inline void bw_satur_init(bw_satur_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_satur_set_sample_rate()
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* ```>>> */
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static inline void bw_satur_set_sample_rate(bw_satur_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_satur_reset_coeffs()
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* ```>>> */
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static inline void bw_satur_reset_coeffs(bw_satur_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_satur_reset_state()
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* ```>>> */
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static inline void bw_satur_reset_state(const bw_satur_coeffs *BW_RESTRICT coeffs, bw_satur_state *BW_RESTRICT state);
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/*! <<<```
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* Resets the given `state` to its initial values using the given `coeffs`.
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*
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* #### bw_satur_update_coeffs_ctrl()
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* ```>>> */
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static inline void bw_satur_update_coeffs_ctrl(bw_satur_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_satur_update_coeffs_audio()
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* ```>>> */
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static inline void bw_satur_update_coeffs_audio(bw_satur_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_satur_process1()
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* ```>>> */
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static inline float bw_satur_process1(const bw_satur_coeffs *BW_RESTRICT coeffs, bw_satur_state *BW_RESTRICT state, float x);
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static inline float bw_satur_process1_comp(const bw_satur_coeffs *BW_RESTRICT coeffs, bw_satur_state *BW_RESTRICT state, float x);
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/*! <<<```
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* These function process one input sample `x` using `coeffs`, while using
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* and updating `state`. They return the corresponding output sample.
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*
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* In particular:
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* * `bw_satur_process1()` assumes that gain compensation is disabled;
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* * `bw_satur_process1_comp()` assumes that gain compensation is enabled.
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*
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* #### bw_satur_process()
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* ```>>> */
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static inline void bw_satur_process(bw_satur_coeffs *BW_RESTRICT coeffs, bw_satur_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_satur_set_bias()
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* ```>>> */
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static inline void bw_satur_set_bias(bw_satur_coeffs *BW_RESTRICT coeffs, float value);
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/*! <<<```
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* Sets the input bias `value` in `coeffs`.
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*
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* Default value: `0.f`.
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*
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* #### bw_satur_set_gain()
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* ```>>> */
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static inline void bw_satur_set_gain(bw_satur_coeffs *BW_RESTRICT coeffs, float value);
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/*! <<<```
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* Sets the gain `value` in `coeffs`.
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*
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* Do not set it to `0.f`, obviously.
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*
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* Default value: `1.f`.
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*
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* #### bw_satur_set_gain_compensation()
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* ```>>> */
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static inline void bw_satur_set_gain_compensation(bw_satur_coeffs *BW_RESTRICT coeffs, char value);
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/*! <<<```
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* Sets whether the output should be divided by gain (`value` non-`0`) or not
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* (`0`).
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*
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* Default value: `1` (on).
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* }}} */
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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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struct _bw_satur_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_bias_state;
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bw_one_pole_state smooth_gain_state;
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// Coefficients
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float bias_dc;
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float inv_gain;
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// Parameters
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float bias;
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float gain;
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char gain_compensation;
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};
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struct _bw_satur_state {
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float x_z1;
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float F_z1;
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};
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static inline float _bw_satur_tanhf_3(float x) {
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const float xm = bw_clipf(x, -2.115287308554551f, 2.115287308554551f);
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const float axm = bw_absf(xm);
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return xm * axm * (0.01218073260037716f * axm - 0.2750231331124371f) + xm;
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}
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static inline void bw_satur_init(bw_satur_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->bias = 0.f;
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coeffs->gain = 1.f;
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coeffs->gain_compensation = 1;
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}
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static inline void bw_satur_set_sample_rate(bw_satur_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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}
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static inline void _bw_satur_do_update_coeffs(bw_satur_coeffs *BW_RESTRICT coeffs, char force) {
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float bias_cur = bw_one_pole_get_y_z1(&coeffs->smooth_bias_state);
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if (force || coeffs->bias != bias_cur) {
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bias_cur = bw_one_pole_process1_sticky_abs(&coeffs->smooth_coeffs, &coeffs->smooth_bias_state, coeffs->bias);
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coeffs->bias_dc = _bw_satur_tanhf_3(bias_cur);
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}
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float gain_cur = bw_one_pole_get_y_z1(&coeffs->smooth_gain_state);
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if (force || coeffs->gain != gain_cur) {
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gain_cur = bw_one_pole_process1_sticky_rel(&coeffs->smooth_coeffs, &coeffs->smooth_gain_state, coeffs->gain);
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coeffs->inv_gain = bw_rcpf_2(gain_cur);
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}
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}
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static inline void bw_satur_reset_coeffs(bw_satur_coeffs *BW_RESTRICT coeffs) {
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bw_one_pole_reset_state(&coeffs->smooth_coeffs, &coeffs->smooth_bias_state, coeffs->bias);
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_bw_satur_do_update_coeffs(coeffs, 1);
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}
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static inline void bw_satur_reset_state(const bw_satur_coeffs *BW_RESTRICT coeffs, bw_satur_state *BW_RESTRICT state) {
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state->F_z1 = 0.f;
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state->x_z1 = 0.f;
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}
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static inline void bw_satur_update_coeffs_ctrl(bw_satur_coeffs *BW_RESTRICT coeffs) {
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}
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static inline void bw_satur_update_coeffs_audio(bw_satur_coeffs *BW_RESTRICT coeffs) {
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_bw_satur_do_update_coeffs(coeffs, 0);
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}
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static inline float bw_satur_process1(const bw_satur_coeffs *BW_RESTRICT coeffs, bw_satur_state *BW_RESTRICT state, float x) {
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x = bw_one_pole_get_y_z1(&coeffs->smooth_gain_state) * x + bw_one_pole_get_y_z1(&coeffs->smooth_bias_state);
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const float ax = bw_absf(x);
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const float F = ax >= 2.115287308554551f ? ax - 0.6847736211329452f : ax * ax * ((0.00304518315009429f * ax - 0.09167437770414569f) * ax + 0.5f);
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const float d = x - state->x_z1;
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const float y = d * d < 1e-6f ? _bw_satur_tanhf_3(0.5f * (x + state->x_z1)) : (F - state->F_z1) * bw_rcpf_2(d);
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state->x_z1 = x;
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state->F_z1 = F;
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return y - coeffs->bias_dc;
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}
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static inline float bw_satur_process1_comp(const bw_satur_coeffs *BW_RESTRICT coeffs, bw_satur_state *BW_RESTRICT state, float x) {
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float y = bw_satur_process1(coeffs, state, x);
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return coeffs->inv_gain * y;
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}
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static inline void bw_satur_process(bw_satur_coeffs *BW_RESTRICT coeffs, bw_satur_state *BW_RESTRICT state, const float *x, float *y, int n_samples) {
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if (coeffs->gain_compensation)
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for (int i = 0; i < n_samples; i++) {
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bw_satur_update_coeffs_audio(coeffs);
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y[i] = bw_satur_process1_comp(coeffs, state, x[i]);
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}
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else
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for (int i = 0; i < n_samples; i++) {
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bw_satur_update_coeffs_audio(coeffs);
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y[i] = bw_satur_process1(coeffs, state, x[i]);
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}
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}
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static inline void bw_satur_set_bias(bw_satur_coeffs *BW_RESTRICT coeffs, float value) {
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coeffs->bias = value;
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}
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static inline void bw_satur_set_gain(bw_satur_coeffs *BW_RESTRICT coeffs, float value) {
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coeffs->gain = value;
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}
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static inline void bw_satur_set_gain_compensation(bw_satur_coeffs *BW_RESTRICT coeffs, char value) {
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coeffs->gain_compensation = 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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