151 lines
4.4 KiB
C
151 lines
4.4 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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* 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 {{{ 0.3.0 }}}
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* requires {{{ bw_config bw_common bw_math }}}
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* description {{{
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* Sample rate reducer.
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*
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* This is purely an audio effect, it doesn't actually produce an output
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* signal at a lower sample rate. The algorithm is deliberately crude to
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* obtain the characteristic aliasing due to lo-fi downsampling.
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* }}}
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* changelog {{{
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* <ul>
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* <li>Version <strong>0.3.0</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_SR_REDUCE_H
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#define _BW_SR_REDUCE_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_sr_reduce_coeffs
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* ```>>> */
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typedef struct _bw_sr_reduce_coeffs bw_sr_reduce_coeffs;
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/*! <<<```
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* Coefficients and related.
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*
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* #### bw_sr_reduce_state
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* ```>>> */
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typedef struct _bw_sr_reduce_state bw_sr_reduce_state;
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/*! <<<```
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* Internal state and related.
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*
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* #### bw_sr_reduce_init()
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* ```>>> */
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static inline void bw_sr_reduce_init(bw_sr_reduce_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_sr_reduce_reset_state()
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* ```>>> */
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static inline void bw_sr_reduce_reset_state(const bw_sr_reduce_coeffs *BW_RESTRICT coeffs, bw_sr_reduce_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_sr_reduce_process1()
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* ```>>> */
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static inline float bw_sr_reduce_process1(const bw_sr_reduce_coeffs *BW_RESTRICT coeffs, bw_sr_reduce_state *BW_RESTRICT state, float x);
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/*! <<<```
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* Processes one input sample `x` using `coeffs`, while using and updating
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* `state`. Returns the corresponding output sample.
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*
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* #### bw_sr_reduce_process()
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* ```>>> */
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static inline void bw_sr_reduce_process(bw_sr_reduce_coeffs *BW_RESTRICT coeffs, bw_sr_reduce_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 `coeffs` and
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* using and updating `state` (control and audio rate).
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*
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* #### bw_sr_reduce_set_ratio()
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* ```>>> */
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static inline void bw_sr_reduce_set_ratio(bw_sr_reduce_coeffs *BW_RESTRICT coeffs, float value);
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/*! <<<```
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* Sets the output to input sample rate ratio in `coeffs`.
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*
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* Valid input range: [`0.f`, `1.f`].
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*
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* Default value: `1.f`.
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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_sr_reduce_coeffs {
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// Parameters
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float ratio;
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};
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struct _bw_sr_reduce_state {
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float phase;
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float y_z1;
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};
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static inline void bw_sr_reduce_init(bw_sr_reduce_coeffs *BW_RESTRICT coeffs) {
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coeffs->ratio = 1.f;
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}
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static inline void bw_sr_reduce_reset_state(const bw_sr_reduce_coeffs *BW_RESTRICT coeffs, bw_sr_reduce_state *BW_RESTRICT state) {
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state->phase = 1.f;
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}
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static inline float bw_sr_reduce_process1(const bw_sr_reduce_coeffs *BW_RESTRICT coeffs, bw_sr_reduce_state *BW_RESTRICT state, float x) {
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state->phase += coeffs->ratio;
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if (state->phase >= 1.f) {
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state->y_z1 = x;
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state->phase -= bw_floorf(state->phase);
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}
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return state->y_z1;
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}
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static inline void bw_sr_reduce_process(bw_sr_reduce_coeffs *BW_RESTRICT coeffs, bw_sr_reduce_state *BW_RESTRICT state, const float *x, float* y, int n_samples) {
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for (int i = 0; i < n_samples; i++)
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y[i] = bw_sr_reduce_process1(coeffs, state, x[i]);
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}
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static inline void bw_sr_reduce_set_ratio(bw_sr_reduce_coeffs *BW_RESTRICT coeffs, float value) {
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coeffs->ratio = 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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