tentative bw_src_int, cosmetic change to bw_svf
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1
TODO
1
TODO
@ -31,6 +31,7 @@ code:
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* MEM_REQ_ROUGH() macro?
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* use BW_SIZE_T, check constant types
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* web examples: need to export memset?
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* cite papers, thank authors
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build system:
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* make makefiles handle paths with spaces etc
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197
include/bw_src_int.h
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197
include/bw_src_int.h
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@ -0,0 +1,197 @@
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/*
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* Brickworks
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*
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* Copyright (C) 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 {{{ 0.4.0 }}}
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* requires {{{ bw_config bw_common bw_math }}}
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* description {{{
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* Integer-ratio IIR sample rate converter.
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*
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* Multi-rate filtering inspired by
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*
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* M. Holters and J.Parker, "A Combined Model for a Bucket Brigade Device and
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* its Input and Output Filters", 21st Intl. Conf. Digital Audio Effects
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* (DAFx-18), Aveiro, Portugal, September 2018.
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* }}}
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* changelog {{{
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* <ul>
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* <li>Version <strong>0.4.0</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_SRC_INT_H
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#define _BW_SRC_INT_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_src_int_coeffs
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* ```>>> */
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typedef struct _bw_src_int_coeffs bw_src_int_coeffs;
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/*! <<<```
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* Coefficients and related.
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*
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* ### bw_src_int_state
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* ```>>> */
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typedef struct _bw_src_int_state bw_src_int_state;
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/*! <<<```
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* Internal state and related.
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*
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* #### bw_src_int_init()
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* ```>>> */
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static inline void bw_src_int_init(bw_src_int_coeffs *BW_RESTRICT coeffs, int ratio);
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/*! <<<```
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* Initializes input parameter values in `coeffs`.
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* XXX
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*
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* #### bw_src_int_reset_state()
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* ```>>> */
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static inline void bw_src_int_reset_state(const bw_src_int_coeffs *BW_RESTRICT coeffs, bw_src_int_state *BW_RESTRICT state, float x0);
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/*! <<<```
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* XXX
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*
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* #### bw_src_int_process()
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* ```>>> */
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static inline int bw_src_int_process(const bw_src_int_coeffs *BW_RESTRICT coeffs, bw_src_int_state *BW_RESTRICT state, const float *x, float *y, int n_in_samples);
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/*! <<<```
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* XXX
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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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struct _bw_src_int_coeffs {
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int ratio;
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float a1;
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float a2;
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float a3;
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float a4;
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float b0;
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float b1;
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float b2;
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float b3;
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float b4;
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};
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struct _bw_src_int_state {
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int i;
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float z1;
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float z2;
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float z3;
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float z4;
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float xz1;
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float xz2;
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float xz3;
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float xz4;
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};
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static inline void bw_src_int_init(bw_src_int_coeffs *BW_RESTRICT coeffs, int ratio) {
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coeffs->ratio = ratio;
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// TODO: better filter, perhaps optimzied coefficients
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ratio = ratio >= 0 ? ratio : -ratio;
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coeffs->a1 = (12.56637061435917f - 8.f * ratio) / (2.f * ratio + 3.141592653589793f);
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coeffs->a2 = (ratio * (24.f * ratio - 75.39822368615503f) + 59.21762640653615f) / (ratio * (4.f * ratio + 12.56637061435917f) + 9.869604401089358f);
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coeffs->a3 = (ratio * ((150.7964473723101f - 32.f * ratio) * ratio - 236.8705056261446f) + 124.0251067211993f) / (ratio * (ratio * (8.f * ratio + 37.69911184307752f) + 59.21762640653615f) + 31.00627668029982f);
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coeffs->a4 = (ratio * (ratio * (ratio * (16.f * ratio - 100.5309649148734f) + 236.8705056261446f) - 248.0502134423985f) + 97.40909103400242f) / (ratio * (ratio * (ratio * (16.f * ratio + 100.5309649148734f) + 236.8705056261446f) + 248.0502134423985f) + 97.40909103400242f);
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coeffs->b0 = 97.40909103400242f / (ratio * (ratio * (ratio * (16.f * ratio + 100.5309649148734f) + 236.8705056261446f) + 248.0502134423985f) + 97.40909103400242f);
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coeffs->b1 = 4.f * coeffs->b0;
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coeffs->b2 = 6.f * coeffs->b0;
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coeffs->b3 = coeffs->b1;
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coeffs->b4 = coeffs->b0;
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}
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static inline void bw_src_int_reset_state(const bw_src_int_coeffs *BW_RESTRICT coeffs, bw_src_int_state *BW_RESTRICT state, float x0) {
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if (coeffs->ratio < 0) {
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// DF-II
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state->z1 = x0 / (1.f + coeffs->a1 + coeffs->a2 + coeffs->a3 + coeffs->a4);
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state->z2 = state->z1;
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state->z3 = state->z2;
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state->z4 = state->z3;
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state->i = -coeffs->ratio;
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} else {
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// DF-I
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state->z1 = x0;
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state->z2 = x0;
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state->z3 = x0;
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state->z4 = x0;
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state->xz1 = x0;
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state->xz2 = x0;
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state->xz3 = x0;
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state->xz4 = x0;
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}
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}
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static inline int bw_src_int_process(const bw_src_int_coeffs *BW_RESTRICT coeffs, bw_src_int_state *BW_RESTRICT state, const float *x, float *y, int n_in_samples) {
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n = 0;
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if (coeffs->ratio < 0) {
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for (int i = 0; i < n_in_samples; i++) {
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// DF-II
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const float z0 = x[i] - coeffs->a1 * state->z1 - coeffs->a2 * state->z2 - coeffs->a3 * state->z3 - coeffs->a4 * state->z4;
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state->i--;
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if (!state->i) {
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state->i = -coeffs->ratio;
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y[n] = coeffs->b0 * z0 + coeffs->b1 * state->z1 + coeffs->b2 * state->z2 + coeffs->b3 * state->z3 + coeffs->b4 * state->z4;
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n++;
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}
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state->z4 = state->z3;
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state->z3 = state->z2;
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state->z2 = state->z1;
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state->z1 = z0;
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}
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} else {
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for (int i = 0; i < n_in_samples; i++) {
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// DF-I
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const float v = coeffs->b0 * x[i] + coeffs->b1 * state->xz1 + coeffs->b2 * state->xz2 + coeffs->b3 * state->xz3 + coeffs->b4 * state->xz4;
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state->xz4 = state->xz3;
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state->xz3 = state->xz2;
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state->xz2 = state->xz1;
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state->xz1 = x[i];
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for (int j = 0; j < coeffs->ratio; j++) {
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y[n] = v - coeffs->a1 * state->z1 - coeffs->a2 * state->z2 - coeffs->a3 * state->z3 - coeffs->a4 * state->z4;
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state->z4 = state->z3;
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state->z3 = state->z2;
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state->z2 = state->z1;
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state->z1 = y[n];
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n++;
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}
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}
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}
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return n;
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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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@ -21,7 +21,7 @@
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/*!
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* module_type {{{ dsp }}}
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* version {{{ 0.3.0 }}}
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* requires {{{ bw_config bw_common bw_one_pole bw_math }}}
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* requires {{{ bw_config bw_common bw_math bw_one_pole }}}
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* description {{{
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* State variable filter (2nd order, 12 dB/oct) model with separated lowpass,
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* bandpass, and highpass outputs.
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