417 lines
13 KiB
C++
417 lines
13 KiB
C++
/*
|
|
* Brickworks
|
|
*
|
|
* Copyright (C) 2022, 2023 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 {{{ 1.0.0 }}}
|
|
* requires {{{ bw_common bw_math bw_one_pole }}}
|
|
* description {{{
|
|
* First-order lowpass filter (6 dB/oct) with unitary DC gain.
|
|
*
|
|
* This is better suited to filtering actual audio than
|
|
* [bw_one_pole](bw_one_pole).
|
|
* }}}
|
|
* changelog {{{
|
|
* <ul>
|
|
* <li>Version <strong>1.0.0</strong>:
|
|
* <ul>
|
|
* <li><code>bw_lp1_process()</code> and
|
|
* <code>bw_lp1_process_multi()</code> now use <code>size_t</code>
|
|
* to count samples and channels.</li>
|
|
* <li>Added more <code>const</code> specifiers to input
|
|
* arguments.</li>
|
|
* <li>Moved C++ code to C header.</li>
|
|
* <li>Added overladed C++ <code>process()</code> function taking
|
|
* C-style arrays as arguments.</li>
|
|
* <li>Removed usage of reserved identifiers.</li>
|
|
* </ul>
|
|
* </li>
|
|
* <li>Version <strong>0.6.0</strong>:
|
|
* <ul>
|
|
* <li>Removed dependency on bw_config.</li>
|
|
* </ul>
|
|
* </li>
|
|
* <li>Version <strong>0.5.0</strong>:
|
|
* <ul>
|
|
* <li>Added <code>bw_lp1_process_multi()</code>.</li>
|
|
* <li>Added C++ wrapper.</li>
|
|
* </ul>
|
|
* </li>
|
|
* <li>Version <strong>0.4.0</strong>:
|
|
* <ul>
|
|
* <li>Added initial input value to
|
|
* <code>bw_lp1_reset_state()</code>.</li>
|
|
* <li>Fixed unused parameter warnings.</li>
|
|
* </ul>
|
|
* </li>
|
|
* <li>Version <strong>0.3.0</strong>:
|
|
* <ul>
|
|
* <li>First release.</li>
|
|
* </ul>
|
|
* </li>
|
|
* </ul>
|
|
* }}}
|
|
*/
|
|
|
|
#ifndef BW_LP1_H
|
|
#define BW_LP1_H
|
|
|
|
#include <bw_common.h>
|
|
|
|
#ifdef __cplusplus
|
|
extern "C" {
|
|
#endif
|
|
|
|
/*! api {{{
|
|
* #### bw_lp1_coeffs
|
|
* ```>>> */
|
|
typedef struct bw_lp1_coeffs bw_lp1_coeffs;
|
|
/*! <<<```
|
|
* Coefficients and related.
|
|
*
|
|
* #### bw_lp1_state
|
|
* ```>>> */
|
|
typedef struct bw_lp1_state bw_lp1_state;
|
|
/*! <<<```
|
|
* Internal state and related.
|
|
*
|
|
* #### bw_lp1_init()
|
|
* ```>>> */
|
|
static inline void bw_lp1_init(bw_lp1_coeffs *BW_RESTRICT coeffs);
|
|
/*! <<<```
|
|
* Initializes input parameter values in `coeffs`.
|
|
*
|
|
* #### bw_lp1_set_sample_rate()
|
|
* ```>>> */
|
|
static inline void bw_lp1_set_sample_rate(bw_lp1_coeffs *BW_RESTRICT coeffs, float sample_rate);
|
|
/*! <<<```
|
|
* Sets the `sample_rate` (Hz) value in `coeffs`.
|
|
*
|
|
* #### bw_lp1_reset_coeffs()
|
|
* ```>>> */
|
|
static inline void bw_lp1_reset_coeffs(bw_lp1_coeffs *BW_RESTRICT coeffs);
|
|
/*! <<<```
|
|
* Resets coefficients in `coeffs` to assume their target values.
|
|
*
|
|
* #### bw_lp1_reset_state()
|
|
* ```>>> */
|
|
static inline void bw_lp1_reset_state(const bw_lp1_coeffs *BW_RESTRICT coeffs, bw_lp1_state *BW_RESTRICT state, float x_0);
|
|
/*! <<<```
|
|
* Resets the given `state` to its initial values using the given `coeffs`
|
|
* and the quiescent/initial input value `x_0`.
|
|
*
|
|
* #### bw_lp1_update_coeffs_ctrl()
|
|
* ```>>> */
|
|
static inline void bw_lp1_update_coeffs_ctrl(bw_lp1_coeffs *BW_RESTRICT coeffs);
|
|
/*! <<<```
|
|
* Triggers control-rate update of coefficients in `coeffs`.
|
|
*
|
|
* #### bw_lp1_update_coeffs_audio()
|
|
* ```>>> */
|
|
static inline void bw_lp1_update_coeffs_audio(bw_lp1_coeffs *BW_RESTRICT coeffs);
|
|
/*! <<<```
|
|
* Triggers audio-rate update of coefficients in `coeffs`.
|
|
*
|
|
* #### bw_lp1_process1()
|
|
* ```>>> */
|
|
static inline float bw_lp1_process1(const bw_lp1_coeffs *BW_RESTRICT coeffs, bw_lp1_state *BW_RESTRICT state, float x);
|
|
/*! <<<```
|
|
* Processes one input sample `x` using `coeffs`, while using and updating
|
|
* `state`. Returns the corresponding output sample.
|
|
*
|
|
* #### bw_lp1_process()
|
|
* ```>>> */
|
|
static inline void bw_lp1_process(bw_lp1_coeffs *BW_RESTRICT coeffs, bw_lp1_state *BW_RESTRICT state, const float *x, float *y, size_t 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_lp1_process_multi()
|
|
* ```>>> */
|
|
static inline void bw_lp1_process_multi(bw_lp1_coeffs *BW_RESTRICT coeffs, bw_lp1_state * const *BW_RESTRICT state, const float * const *x, float **y, size_t n_channels, size_t n_samples);
|
|
/*! <<<```
|
|
* Processes the first `n_samples` of the `n_channels` input buffers `x` and
|
|
* fills the first `n_samples` of the `n_channels` output buffers `y`, while
|
|
* using and updating both the common `coeffs` and each of the `n_channels`
|
|
* `state`s (control and audio rate).
|
|
*
|
|
* #### bw_lp1_set_cutoff()
|
|
* ```>>> */
|
|
static inline void bw_lp1_set_cutoff(bw_lp1_coeffs *BW_RESTRICT coeffs, float value);
|
|
/*! <<<```
|
|
* Sets the cutoff frequency `value` (Hz) in `coeffs`.
|
|
*
|
|
* Default value: `1e3f`.
|
|
*
|
|
* #### bw_lp1_set_prewarp_at_cutoff()
|
|
* ```>>> */
|
|
static inline void bw_lp1_set_prewarp_at_cutoff(bw_lp1_coeffs *BW_RESTRICT coeffs, char value);
|
|
/*! <<<```
|
|
* Sets whether bilinear transform prewarping frequency should match the
|
|
* cutoff frequency (non-`0`) or not (`0`).
|
|
*
|
|
* Default value: non-`0` (on).
|
|
*
|
|
* #### bw_lp1_set_prewarp_freq()
|
|
* ```>>> */
|
|
static inline void bw_lp1_set_prewarp_freq(bw_lp1_coeffs *BW_RESTRICT coeffs, float value);
|
|
/*! <<<```
|
|
* Sets the prewarping frequency `value` (Hz) in `coeffs`.
|
|
*
|
|
* Only used when the prewarp\_at\_cutoff parameter is off.
|
|
*
|
|
* Default value: `1e3f`.
|
|
* }}} */
|
|
|
|
#ifdef __cplusplus
|
|
}
|
|
#endif
|
|
|
|
/*** 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. */
|
|
|
|
#include <bw_math.h>
|
|
#include <bw_one_pole.h>
|
|
|
|
#ifdef __cplusplus
|
|
extern "C" {
|
|
#endif
|
|
|
|
struct bw_lp1_coeffs {
|
|
// Sub-components
|
|
bw_one_pole_coeffs smooth_coeffs;
|
|
bw_one_pole_state smooth_cutoff_state;
|
|
bw_one_pole_state smooth_prewarp_freq_state;
|
|
|
|
// Coefficients
|
|
float t_k;
|
|
|
|
float prewarp_k;
|
|
float t;
|
|
float X_x;
|
|
float X_X_z1;
|
|
float y_X;
|
|
|
|
// Parameters
|
|
float cutoff;
|
|
float prewarp_freq;
|
|
};
|
|
|
|
struct bw_lp1_state {
|
|
float y_z1;
|
|
float X_z1;
|
|
};
|
|
|
|
static inline void bw_lp1_init(bw_lp1_coeffs *BW_RESTRICT coeffs) {
|
|
bw_one_pole_init(&coeffs->smooth_coeffs);
|
|
bw_one_pole_set_tau(&coeffs->smooth_coeffs, 0.005f);
|
|
bw_one_pole_set_sticky_thresh(&coeffs->smooth_coeffs, 1e-3f);
|
|
coeffs->cutoff = 1e3f;
|
|
coeffs->prewarp_freq = 1e3f;
|
|
coeffs->prewarp_k = 1.f;
|
|
}
|
|
|
|
static inline void bw_lp1_set_sample_rate(bw_lp1_coeffs *BW_RESTRICT coeffs, float sample_rate) {
|
|
bw_one_pole_set_sample_rate(&coeffs->smooth_coeffs, sample_rate);
|
|
bw_one_pole_reset_coeffs(&coeffs->smooth_coeffs);
|
|
coeffs->t_k = 3.141592653589793f / sample_rate;
|
|
}
|
|
|
|
static inline void bw_lp1_do_update_coeffs(bw_lp1_coeffs *BW_RESTRICT coeffs, char force) {
|
|
const float prewarp_freq = coeffs->prewarp_freq + coeffs->prewarp_k * (coeffs->cutoff - coeffs->prewarp_freq);
|
|
float prewarp_freq_cur = bw_one_pole_get_y_z1(&coeffs->smooth_prewarp_freq_state);
|
|
float cutoff_cur = bw_one_pole_get_y_z1(&coeffs->smooth_cutoff_state);
|
|
const char prewarp_freq_changed = force || prewarp_freq != prewarp_freq_cur;
|
|
const char cutoff_changed = force || coeffs->cutoff != cutoff_cur;
|
|
if (prewarp_freq_changed || cutoff_changed) {
|
|
if (prewarp_freq_changed) {
|
|
prewarp_freq_cur = bw_one_pole_process1_sticky_rel(&coeffs->smooth_coeffs, &coeffs->smooth_prewarp_freq_state, prewarp_freq);
|
|
coeffs->t = bw_tanf(coeffs->t_k * prewarp_freq_cur);
|
|
}
|
|
if (cutoff_changed) {
|
|
cutoff_cur = bw_one_pole_process1_sticky_rel(&coeffs->smooth_coeffs, &coeffs->smooth_cutoff_state, coeffs->cutoff);
|
|
coeffs->y_X = bw_rcpf(cutoff_cur);
|
|
}
|
|
const float k = cutoff_cur * bw_rcpf(cutoff_cur * coeffs->t + prewarp_freq_cur);
|
|
coeffs->X_x = k * prewarp_freq_cur;
|
|
coeffs->X_X_z1 = k * coeffs->t;
|
|
}
|
|
}
|
|
|
|
static inline void bw_lp1_reset_coeffs(bw_lp1_coeffs *BW_RESTRICT coeffs) {
|
|
bw_one_pole_reset_state(&coeffs->smooth_coeffs, &coeffs->smooth_cutoff_state, coeffs->cutoff);
|
|
bw_one_pole_reset_state(&coeffs->smooth_coeffs, &coeffs->smooth_prewarp_freq_state, coeffs->prewarp_freq + coeffs->prewarp_k * (coeffs->cutoff - coeffs->prewarp_freq));
|
|
bw_lp1_do_update_coeffs(coeffs, 1);
|
|
}
|
|
|
|
static inline void bw_lp1_reset_state(const bw_lp1_coeffs *BW_RESTRICT coeffs, bw_lp1_state *BW_RESTRICT state, float x_0) {
|
|
(void)coeffs;
|
|
state->y_z1 = x_0;
|
|
state->X_z1 = 0.f;
|
|
}
|
|
|
|
static inline void bw_lp1_update_coeffs_ctrl(bw_lp1_coeffs *BW_RESTRICT coeffs) {
|
|
(void)coeffs;
|
|
}
|
|
|
|
static inline void bw_lp1_update_coeffs_audio(bw_lp1_coeffs *BW_RESTRICT coeffs) {
|
|
bw_lp1_do_update_coeffs(coeffs, 0);
|
|
}
|
|
|
|
static inline float bw_lp1_process1(const bw_lp1_coeffs *BW_RESTRICT coeffs, bw_lp1_state *BW_RESTRICT state, float x) {
|
|
const float X = coeffs->X_x * (x - state->y_z1) - coeffs->X_X_z1 * state->X_z1;
|
|
const float y = x - coeffs->y_X * X;
|
|
state->y_z1 = y;
|
|
state->X_z1 = X;
|
|
return y;
|
|
}
|
|
|
|
static inline void bw_lp1_process(bw_lp1_coeffs *BW_RESTRICT coeffs, bw_lp1_state *BW_RESTRICT state, const float *x, float *y, size_t n_samples) {
|
|
for (size_t i = 0; i < n_samples; i++) {
|
|
bw_lp1_update_coeffs_audio(coeffs);
|
|
y[i] = bw_lp1_process1(coeffs, state, x[i]);
|
|
}
|
|
}
|
|
|
|
static inline void bw_lp1_process_multi(bw_lp1_coeffs *BW_RESTRICT coeffs, bw_lp1_state * const *BW_RESTRICT state, const float * const *x, float **y, size_t n_channels, size_t n_samples) {
|
|
for (size_t i = 0; i < n_samples; i++) {
|
|
bw_lp1_update_coeffs_audio(coeffs);
|
|
for (size_t j = 0; j < n_channels; j++)
|
|
y[j][i] = bw_lp1_process1(coeffs, state[j], x[j][i]);
|
|
}
|
|
}
|
|
|
|
static inline void bw_lp1_set_cutoff(bw_lp1_coeffs *BW_RESTRICT coeffs, float value) {
|
|
coeffs->cutoff = value;
|
|
}
|
|
|
|
static inline void bw_lp1_set_prewarp_at_cutoff(bw_lp1_coeffs *BW_RESTRICT coeffs, char value) {
|
|
coeffs->prewarp_k = value ? 1.f : 0.f;
|
|
}
|
|
|
|
static inline void bw_lp1_set_prewarp_freq(bw_lp1_coeffs *BW_RESTRICT coeffs, float value) {
|
|
coeffs->prewarp_freq = value;
|
|
}
|
|
|
|
#ifdef __cplusplus
|
|
}
|
|
|
|
#include <array>
|
|
|
|
namespace Brickworks {
|
|
|
|
/*** Public C++ API ***/
|
|
|
|
/*! api_cpp {{{
|
|
* ##### Brickworks::LP1
|
|
* ```>>> */
|
|
template<size_t N_CHANNELS>
|
|
class LP1 {
|
|
public:
|
|
LP1();
|
|
|
|
void setSampleRate(float sampleRate);
|
|
void reset(float x_0 = 0.f);
|
|
void process(
|
|
const float * const *x,
|
|
float **y,
|
|
size_t nSamples);
|
|
void process(
|
|
std::array<const float *, N_CHANNELS> x,
|
|
std::array<float *, N_CHANNELS> y,
|
|
size_t nSamples);
|
|
|
|
void setCutoff(float value);
|
|
void setPrewarpAtCutoff(bool value);
|
|
void setPrewarpFreq(float value);
|
|
/*! <<<...
|
|
* }
|
|
* ```
|
|
* }}} */
|
|
|
|
/*** 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. */
|
|
|
|
private:
|
|
bw_lp1_coeffs coeffs;
|
|
bw_lp1_state states[N_CHANNELS];
|
|
bw_lp1_state *statesP[N_CHANNELS];
|
|
};
|
|
|
|
template<size_t N_CHANNELS>
|
|
inline LP1<N_CHANNELS>::LP1() {
|
|
bw_lp1_init(&coeffs);
|
|
for (size_t i = 0; i < N_CHANNELS; i++)
|
|
statesP[i] = states + i;
|
|
}
|
|
|
|
template<size_t N_CHANNELS>
|
|
inline void LP1<N_CHANNELS>::setSampleRate(float sampleRate) {
|
|
bw_lp1_set_sample_rate(&coeffs, sampleRate);
|
|
}
|
|
|
|
template<size_t N_CHANNELS>
|
|
inline void LP1<N_CHANNELS>::reset(float x_0) {
|
|
bw_lp1_reset_coeffs(&coeffs);
|
|
for (size_t i = 0; i < N_CHANNELS; i++)
|
|
bw_lp1_reset_state(&coeffs, states + i, x_0);
|
|
}
|
|
|
|
template<size_t N_CHANNELS>
|
|
inline void LP1<N_CHANNELS>::process(
|
|
const float * const *x,
|
|
float **y,
|
|
size_t nSamples) {
|
|
bw_lp1_process_multi(&coeffs, statesP, x, y, N_CHANNELS, nSamples);
|
|
}
|
|
|
|
template<size_t N_CHANNELS>
|
|
inline void LP1<N_CHANNELS>::process(
|
|
std::array<const float *, N_CHANNELS> x,
|
|
std::array<float *, N_CHANNELS> y,
|
|
size_t nSamples) {
|
|
process(x.data(), y.data(), nSamples);
|
|
}
|
|
|
|
template<size_t N_CHANNELS>
|
|
inline void LP1<N_CHANNELS>::setCutoff(float value) {
|
|
bw_lp1_set_cutoff(&coeffs, value);
|
|
}
|
|
|
|
template<size_t N_CHANNELS>
|
|
inline void LP1<N_CHANNELS>::setPrewarpAtCutoff(bool value) {
|
|
bw_lp1_set_prewarp_at_cutoff(&coeffs, value);
|
|
}
|
|
|
|
template<size_t N_CHANNELS>
|
|
inline void LP1<N_CHANNELS>::setPrewarpFreq(float value) {
|
|
bw_lp1_set_prewarp_freq(&coeffs, value);
|
|
}
|
|
|
|
}
|
|
#endif
|
|
|
|
#endif
|