213 lines
7.2 KiB
C
213 lines
7.2 KiB
C
/*
|
||
* Brickworks
|
||
*
|
||
* Copyright (C) 2022 Orastron Srl unipersonale
|
||
*
|
||
* Brickworks is free software: you can redistribute it and/or modify
|
||
* it under the terms of the GNU General Public License as published by
|
||
* the Free Software Foundation, version 3 of the License.
|
||
*
|
||
* Brickworks is distributed in the hope that it will be useful,
|
||
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||
* GNU General Public License for more details.
|
||
*
|
||
* You should have received a copy of the GNU General Public License
|
||
* along with Brickworks. If not, see <http://www.gnu.org/licenses/>.
|
||
*
|
||
* File author: Stefano D'Angelo
|
||
*/
|
||
|
||
/*!
|
||
* module_type {{{ dsp }}}
|
||
* version {{{ 0.2.1 }}}
|
||
* requires {{{ bw_config bw_common }}}
|
||
* description {{{
|
||
* Pinking filter.
|
||
*
|
||
* This is a
|
||
* <a href="https://en.wikipedia.org/wiki/Linear_time-invariant_system"
|
||
* target="_blank">linear time-invariant filter</a> approximately attenuating
|
||
* 3 dB/oct from about 0.000046 × Nyquist frequency to about 0.9 × Nyquist
|
||
* frequency. It can be used to turn white noise into pink noise (hence the
|
||
* name).
|
||
* }}}
|
||
* changelog {{{
|
||
* <ul>
|
||
* <li>Version <strong>0.2.1</strong>:
|
||
* <ul>
|
||
* <li>Added missing documentation for
|
||
* <code>bw_pink_filt_coeffs</code>.</li>
|
||
* </ul>
|
||
* </li>
|
||
* <li>Version <strong>0.2.0</strong>:
|
||
* <ul>
|
||
* <li>Refactored API.</li>
|
||
* </ul>
|
||
* </li>
|
||
* <li>Version <strong>0.1.0</strong>:
|
||
* <ul>
|
||
* <li>First release.</li>
|
||
* </ul>
|
||
* </li>
|
||
* </ul>
|
||
* }}}
|
||
*/
|
||
|
||
#ifndef _BW_PINK_FILT_H
|
||
#define _BW_PINK_FILT_H
|
||
|
||
#ifdef __cplusplus
|
||
extern "C" {
|
||
#endif
|
||
|
||
#include <bw_common.h>
|
||
|
||
/*! api {{{
|
||
* #### bw_pink_filt_coeffs
|
||
* ```>>> */
|
||
typedef struct _bw_pink_filt_coeffs bw_pink_filt_coeffs;
|
||
/*! <<<```
|
||
* Coefficients and related.
|
||
*
|
||
* #### bw_pink_filt_state
|
||
* ```>>> */
|
||
typedef struct _bw_pink_filt_state bw_pink_filt_state;
|
||
/*! <<<```
|
||
* Internal state and related.
|
||
*
|
||
* #### bw_pink_filt_init()
|
||
* ```>>> */
|
||
static inline void bw_pink_filt_init(bw_pink_filt_coeffs *BW_RESTRICT coeffs);
|
||
/*! <<<```
|
||
* Initializes input parameter values in `coeffs`.
|
||
*
|
||
* #### bw_pink_filt_set_sample_rate()
|
||
* ```>>> */
|
||
static inline void bw_pink_filt_set_sample_rate(bw_pink_filt_coeffs *BW_RESTRICT coeffs, float sample_rate);
|
||
/*! <<<```
|
||
* Sets the `sample_rate` (Hz) value in `coeffs`.
|
||
*
|
||
* #### bw_pink_filt_reset_state()
|
||
* ```>>> */
|
||
static inline void bw_pink_filt_reset_state(const bw_pink_filt_coeffs *BW_RESTRICT coeffs, bw_pink_filt_state *BW_RESTRICT state);
|
||
/*! <<<```
|
||
* Resets the given `state` to its initial values using the given `coeffs`.
|
||
*
|
||
* #### bw_pink_filt_process1()
|
||
* ```>>> */
|
||
static inline float bw_pink_filt_process1(const bw_pink_filt_coeffs *BW_RESTRICT coeffs, bw_pink_filt_state *BW_RESTRICT state, float x);
|
||
static inline float bw_pink_filt_process1_scaling(const bw_pink_filt_coeffs *BW_RESTRICT coeffs, bw_pink_filt_state *BW_RESTRICT state, float x);
|
||
/*! <<<```
|
||
* These function process one input sample `x` using `coeffs`, while using
|
||
* and updating `state`. They return the corresponding output sample.
|
||
*
|
||
* In particular:
|
||
* * `bw_pink_filt_process1()` assumes that sample rate scaling is disabled;
|
||
* * `bw_pink_filt_process1_scaling()` assumes that sample rate scaling is
|
||
* enabled.
|
||
*
|
||
* #### bw_pink_filt_process()
|
||
* ```>>> */
|
||
static inline void bw_pink_filt_process(bw_pink_filt_coeffs *BW_RESTRICT coeffs, bw_pink_filt_state *BW_RESTRICT state, const float *x, float* y, int n_samples);
|
||
/*! <<<```
|
||
* Processes the first `n_samples` of the input buffer `x` and fills the
|
||
* first `n_samples` of the output buffer `y`, while using and updating both
|
||
* `coeffs` and `state` (control and audio rate).
|
||
*
|
||
* #### bw_pink_filt_set_sample_rate_scaling()
|
||
* ```>>> */
|
||
static inline void bw_pink_filt_set_sample_rate_scaling(bw_noise_gen_coeffs *BW_RESTRICT coeffs, char value);
|
||
/*! <<<```
|
||
* Sets whether the output should be scaled (`value` non-`0`) or not (`0`)
|
||
* according to the sample rate in `coeffs`.
|
||
*
|
||
* In order to keep the magnitude response consistent at different sample
|
||
* rates, the output of this filter should be accordingly scaled. The 44100
|
||
* Hz sample rate is used as a reference (that is, the scaling factor at that
|
||
* sample rate is `1.f`).
|
||
*
|
||
* Default value: `0` (off).
|
||
*
|
||
* #### bw_pink_filt_get_scaling_k()
|
||
* ```>>> */
|
||
static inline float bw_pink_filt_get_scaling_k(const bw_pink_filt_coeffs *BW_RESTRICT coeffs);
|
||
/*! <<<```
|
||
* Returns the sample rate scaling factor that is applied or would be applied
|
||
* if sample rate scaling were enabled, as stored in `coeffs`.
|
||
* }}} */
|
||
|
||
/*** Implementation ***/
|
||
|
||
/* WARNING: This part of the file is not part of the public API. Its content may
|
||
* change at any time in future versions. Please, do not use it directly. */
|
||
|
||
struct _bw_pink_filt_coeffs {
|
||
// Coefficients
|
||
float scaling_k;
|
||
|
||
// Parameters
|
||
float sample_rate_scaling;
|
||
};
|
||
|
||
struct _bw_pink_filt_state {
|
||
float s1_z1;
|
||
float s2_z1;
|
||
float s3_z1;
|
||
float s4_z1;
|
||
};
|
||
|
||
static inline void bw_pink_filt_init(bw_pink_filt_coeffs *BW_RESTRICT coeffs) {
|
||
coeffs->sample_rate_scaling = 0;
|
||
}
|
||
|
||
static inline void bw_pink_filt_set_sample_rate(bw_pink_filt_coeffs *BW_RESTRICT coeffs, float sample_rate) {
|
||
coeffs->scaling_k = 210.f / bw_sqrtf_2(sample_rate);
|
||
}
|
||
|
||
static inline void bw_pink_filt_reset_state(const bw_pink_filt_coeffs *BW_RESTRICT coeffs, bw_pink_filt_state *BW_RESTRICT state) {
|
||
state->s1_z1 = 0.f;
|
||
state->s2_z1 = 0.f;
|
||
state->s3_z1 = 0.f;
|
||
state->s4_z1 = 0.f;
|
||
}
|
||
|
||
static inline float bw_pink_filt_process1(const bw_pink_filt_coeffs *BW_RESTRICT coeffs, bw_pink_filt_state *BW_RESTRICT state, float x) {
|
||
const float s1 = 0.320696754235142f * x + state->s1_z1;
|
||
state->s1_z1 = 0.999760145116749f * s1 - 0.3204568993518913f * x;
|
||
const float s2 = 0.2870206617007935f * s1 + state->s2_z1;
|
||
state->s2_z1 = 0.9974135207366259f * s2 - 0.2844341824374191f * s1;
|
||
const float s3 = 0.2962862885898576f * s2 + state->s3_z1;
|
||
state->s3_z1 = 0.9687905029568185f * s3 - 0.265076791546676f * s2;
|
||
const float s4 = 0.3882183163519794f * s3 + state->s4_z1;
|
||
state->s4_z1 = 0.6573784623288251f * s4 - 0.04559677868080467 * s3;
|
||
return s4;
|
||
}
|
||
|
||
static inline float bw_pink_filt_process1_scaling(const bw_pink_filt_coeffs *BW_RESTRICT coeffs, bw_pink_filt_state *BW_RESTRICT state, float x) {
|
||
return coeffs->scaling_k * bw_pink_filt_process1(coeffs, state, x);
|
||
}
|
||
|
||
static inline void bw_pink_filt_process(bw_pink_filt_coeffs *BW_RESTRICT coeffs, bw_pink_filt_state *BW_RESTRICT state, const float *x, float* y, int n_samples) {
|
||
if (coeffs->sample_rate_scaling)
|
||
for (int i = 0; i < n_samples; i++)
|
||
y[i] = bw_pink_filt_process1_scaling(coeffs, state, x[i]);
|
||
else
|
||
for (int i = 0; i < n_samples; i++)
|
||
y[i] = bw_pink_filt_process1(coeffs, state, x[i]);
|
||
}
|
||
|
||
static inline void bw_pink_filt_set_sample_rate_scaling(bw_noise_gen_coeffs *BW_RESTRICT coeffs, char value) {
|
||
coeffs->sample_rate_scaling = value;
|
||
}
|
||
|
||
static inline float bw_pink_filt_get_scaling_k(const bw_pink_filt_coeffs *BW_RESTRICT coeffs) {
|
||
return coeffs->scaling_k;
|
||
}
|
||
|
||
#ifdef __cplusplus
|
||
}
|
||
#endif
|
||
|
||
#endif
|