new module bw_allpass1 (untested)

TODO

@@ -15,7 +15,7 @@ code:
 * fix vst3 mapped values (visible in Ableton Live) and short names
 * polish examples (ranges, etc.)
 * change name of vst3 template folders to something that doesn't look like a vst3 folder itself
-* how can we only compute bit depth reduction when the input changes in bw_fx_bitcrush?
+* compute bit depth reduction only when input changes? (state)
 
 build system:
 * make makefiles handle paths with spaces etc

include/bw_allpass1.h

@@ -0,0 +1,195 @@
+/*
+ * 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 {{{ 0.3.0 }}}
+ *  requires {{{ bw_config bw_common bw_math }}}
+ *  description {{{
+ *    First-order allpass filter.
+ *  }}}
+ *  changelog {{{
+ *    <ul>
+ *      <li>Version <strong>0.3.0</strong>:
+ *        <ul>
+ *          <li>First release.</li>
+ *        </ul>
+ *      </li>
+ *    </ul>
+ *  }}}
+ */
+
+#ifndef _BW_ALLPASS1_H
+#define _BW_ALLPASS1_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <bw_common.h>
+
+/*! api {{{
+ *    #### bw_allpass1_coeffs
+ *  ```>>> */
+typedef struct _bw_allpass1_coeffs bw_allpass1_coeffs;
+/*! <<<```
+ *    Coefficients and related.
+ *
+ *    #### bw_allpass1_state
+ *  ```>>> */
+typedef struct _bw_allpass1_state bw_allpass1_state;
+/*! <<<```
+ *    Internal state and related.
+ *
+ *    #### bw_allpass1_init()
+ *  ```>>> */
+static inline void bw_allpass1_init(bw_allpass1_coeffs *BW_RESTRICT coeffs);
+/*! <<<```
+ *    Initializes input parameter values in `coeffs`.
+ *
+ *    #### bw_allpass1_set_sample_rate()
+ *  ```>>> */
+static inline void bw_allpass1_set_sample_rate(bw_allpass1_coeffs *BW_RESTRICT coeffs, float sample_rate);
+/*! <<<```
+ *    Sets the `sample_rate` (Hz) value in `coeffs`.
+ *
+ *    #### bw_allpass1_reset_coeffs()
+ *  ```>>> */
+static inline void bw_allpass1_reset_coeffs(bw_allpass1_coeffs *BW_RESTRICT coeffs);
+/*! <<<```
+ *    Resets coefficients in `coeffs` to assume their target values.
+ *
+ *    #### bw_allpass1_reset_state()
+ *  ```>>> */
+static inline void bw_allpass1_reset_state(const bw_allpass1_coeffs *BW_RESTRICT coeffs, bw_allpass1_state *BW_RESTRICT state);
+/*! <<<```
+ *    Resets the given `state` to its initial values using the given `coeffs`.
+ *
+ *    #### bw_allpass1_update_coeffs_ctrl()
+ *  ```>>> */
+static inline void bw_allpass1_update_coeffs_ctrl(bw_allpass1_coeffs *BW_RESTRICT coeffs);
+/*! <<<```
+ *    Triggers control-rate update of coefficients in `coeffs`.
+ *
+ *    #### bw_allpass1_update_coeffs_audio()
+ *  ```>>> */
+static inline void bw_allpass1_update_coeffs_audio(bw_allpass1_coeffs *BW_RESTRICT coeffs);
+/*! <<<```
+ *    Triggers audio-rate update of coefficients in `coeffs`.
+ *
+ *    #### bw_allpass1_process1()
+ *  ```>>> */
+static inline float bw_allpass1_process1(const bw_allpass1_coeffs *BW_RESTRICT coeffs, bw_allpass1_state *BW_RESTRICT state, float x);
+/*! <<<```
+ *    Processes one input sample `x` using `coeffs`, while using and updating
+ *    `state`. Returns the corresponding output sample.
+ *
+ *    #### bw_allpass1_process()
+ *  ```>>> */
+static inline void bw_allpass1_process(bw_allpass1_coeffs *BW_RESTRICT coeffs, bw_allpass1_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_allpass1_set_cutoff()
+ *  ```>>> */
+static inline void bw_allpass1_set_cutoff(bw_allpass1_coeffs *BW_RESTRICT coeffs, float value);
+/*! <<<```
+ *    Sets the cutoff frequency `value` (Hz) in `coeffs`.
+ *
+ *    Default value: `1e3f`.
+ *  }}} */
+
+/*** 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>
+
+struct _bw_allpass1_coeffs {
+	// Coefficients
+	float	t_k;
+
+	float	t;
+	float	X_k;
+
+	// Parameters
+	float	cutoff;
+	float	cutoff_prev;
+};
+
+struct _bw_allpass1_state {
+	float	lp_z1;
+	float	X_z1;
+};
+
+static inline void bw_allpass1_init(bw_allpass1_coeffs *BW_RESTRICT coeffs) {
+	coeffs->cutoff = 1e3f;
+}
+
+static inline void bw_allpass1_set_sample_rate(bw_allpass1_coeffs *BW_RESTRICT coeffs, float sample_rate) {
+	coeffs->t_k = 3.141592653589793f / sample_rate;
+}
+
+static inline void bw_allpass1_reset_coeffs(bw_allpass1_coeffs *BW_RESTRICT coeffs) {
+	coeffs->cutoff_prev = -1.f;
+	bw_allpass1_update_coeffs_ctrl(coeffs);
+}
+
+static inline void bw_allpass1_reset_state(const bw_allpass1_coeffs *BW_RESTRICT coeffs, bw_allpass1_state *BW_RESTRICT state) {
+	state->lp_z1 = 0.f;
+	state->X_z1 = 0.f;
+}
+
+static inline void bw_allpass1_update_coeffs_ctrl(bw_allpass1_coeffs *BW_RESTRICT coeffs) {
+	if (coeffs->cutoff != coeffs->cutoff_prev) {
+		coeffs->t = bw_tanf_3(coeffs->t_k * coeffs->cutoff);
+		coeffs->X_k = bw_rcpf_2(1,f + coeffs->t);
+		coeffs->cutoff_prev = coeffs->cutoff;
+	}
+}
+
+static inline void bw_allpass1_update_coeffs_audio(bw_allpass1_coeffs *BW_RESTRICT coeffs) {
+}
+
+static inline float bw_allpass1_process1(const bw_allpass1_coeffs *BW_RESTRICT coeffs, bw_allpass1_state *BW_RESTRICT state, float x) {
+	const float X = coeffs->X_k * (x - state->lp_z1 - coeffs->t * state->X_z1);
+	const float lp = x - X;
+	state->X_z1 = X;
+	state->lp_z1 = lp;
+	return lp + lp - x;
+}
+
+static inline void bw_allpass1_process(bw_allpass1_coeffs *BW_RESTRICT coeffs, bw_allpass1_state *BW_RESTRICT state, const float *x, float *y, int n_samples) {
+	for (int i = 0; i < n_samples; i++)
+		y[i] = bw_allpass1_process1(coeffs, state, x[i]);
+}
+
+static inline void bw_allpass1_set_cutoff(bw_allpass1_coeffs *BW_RESTRICT coeffs, float value) {
+	coeffs->cutoff = value;
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif