342 lines
11 KiB
C++
342 lines
11 KiB
C++
/*
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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 {{{ 1.0.0 }}}
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* requires {{{ 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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* The multi-rate filtering approach was 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>1.0.0</strong>:
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* <ul>
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* <li><code>Fixed frequency response and improved speed.</code></li>
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* <li><code>bw_src_int_lim_process()</code> and
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* <code>bw_src_int_lim_process_multi()</code> now use
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* <code>size_t</code> to count samples and channels.</li>
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* <li>Added more <code>const</code> and <code>BW_RESTRICT</code>
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* specifiers to input arguments and implementation.</li>
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* <li>Moved C++ code to C header.</li>
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* <li>Added overloaded C++ <code>process()</code> function taking
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* C-style arrays as arguments.</li>
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* <li>Removed usage of reserved identifiers.</li>
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* <li>Clarified that the same buffer cannot be used for both input and
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* output.</li>
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* </ul>
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* </li>
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* <li>Version <strong>0.6.0</strong>:
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* <ul>
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* <li>Removed dependency on bw_config.</li>
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* </ul>
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* </li>
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* <li>Version <strong>0.5.0</strong>:
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* <ul>
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* <li>Added <code>bw_src_int_process_multi()</code>.</li>
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* <li>Added C++ wrapper.</li>
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* </ul>
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* </li>
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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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#include <bw_common.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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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 `coeffs` using the given resampling `ratio`.
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*
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* If `ratio` is positive, then the sample rate of the output signal will be
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* `ratio` times the sample rate of the input signal, otherwise, if it is
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* negative, then the sample rate of the output signal will be equal to the
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* sample rate of the input signal divided by `-ratio`. `ratio` *MUST NOT* be
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* in [`-1`, `1`].
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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 x_0);
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/*! <<<```
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* Resets the given `state` to its initial values using the given `coeffs`
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* and the quiescent/initial input value `x_0`.
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*
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* #### bw_src_int_process()
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* ```>>> */
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static inline size_t bw_src_int_process(const bw_src_int_coeffs *BW_RESTRICT coeffs, bw_src_int_state *BW_RESTRICT state, const float *BW_RESTRICT x, float *BW_RESTRICT y, size_t n_in_samples);
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/*! <<<```
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* Processes the first `n_in_samples` of the input buffer `x` and fills the
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* output buffer `y` using `coeffs`, while using and updating `state`.
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*
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* The number of generated output samples will be `ratio` times
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* `n_in_samples` if `ratio` is positive, otherwise at most `n_in_samples`
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* divided by `-ratio` and then rounded towards positive infinity.
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*
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* `x` and `y` must point to different buffers.
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*
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* Returns the number of generated output samples.
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*
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* #### bw_src_int_process_multi()
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* ```>>> */
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static inline void bw_src_int_process_multi(const bw_src_int_coeffs *BW_RESTRICT coeffs, bw_src_int_state *BW_RESTRICT const *BW_RESTRICT state, const float * const *BW_RESTRICT x, float *BW_RESTRICT const *BW_RESTRICT y, size_t *BW_RESTRICT n, size_t n_channels, size_t n_in_samples);
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/*! <<<```
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* Processes the first `n_in_samples` of the `n_channels` input buffers `x`
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* and fills the `n_channels` output buffers `y` using `coeffs`, while using
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* and updating each of the `n_channels` `state`s.
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*
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* The number of generated output samples in each output buffer will be
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* `ratio` times `n_in_samples` if `ratio` is positive, otherwise at most
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* `n_in_samples` divided by `-ratio` and then rounded towards positive
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* infinity.
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*
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* A given buffer cannot be used both as an input and output buffer.
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*
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* `n` is filled with the number of generated output samples for each output
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* buffer, if not `NULL`.
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* }}} */
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#ifdef __cplusplus
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}
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#endif
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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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#ifdef __cplusplus
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extern "C" {
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#endif
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struct bw_src_int_coeffs {
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int ratio;
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float b0;
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float ma1;
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float ma2;
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float ma3;
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float ma4;
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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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};
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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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// 4th-degree Butterworth with cutoff at ratio * Nyquist, using bilinear transform w/ prewarping
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const float fc = (float)(ratio >= 0 ? ratio : -ratio);
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const float T = bw_tanf(1.570796326794896f / fc);
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const float T2 = T * T;
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const float k = 1.f / (T * (T * (T * (T + 2.613125929752753f) + 3.414213562373095f) + 2.613125929752753f) + 1.f);
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coeffs->b0 = k * T2 * T2;
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coeffs->ma1 = k * (T * (T2 * (-5.226251859505504f - 4.f * T) + 5.226251859505504f) + 4.f);
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coeffs->ma2 = k * ((6.82842712474619f - 6.f * T2) * T2 - 6.f);
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coeffs->ma3 = k * (T * (T2 * (5.226251859505504f - 4.f * T) - 5.226251859505504f) + 4.f);
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coeffs->ma4 = k * (T * (T * ((2.613125929752753f - T) * T - 3.414213562373095f) + 2.613125929752753f) - 1.f);
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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 x_0) {
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if (coeffs->ratio < 0) {
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// DF-II
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state->z1 = x_0 / (1.f - coeffs->ma1 - coeffs->ma2 - coeffs->ma3 - coeffs->ma4);
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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 = 0;
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} else {
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// TDF-II
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const float k = 4.f * coeffs->b0;
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state->z4 = (coeffs->b0 + coeffs->ma4) * x_0;
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state->z3 = (k + coeffs->ma3) * x_0 + state->z4;
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state->z2 = (6.f * coeffs->b0 + coeffs->ma2) * x_0 + state->z3;
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state->z1 = (k + coeffs->ma1) * x_0 + state->z2;
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}
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}
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static inline size_t bw_src_int_process(const bw_src_int_coeffs *BW_RESTRICT coeffs, bw_src_int_state *BW_RESTRICT state, const float *BW_RESTRICT x, float *BW_RESTRICT y, size_t n_in_samples) {
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size_t n = 0;
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if (coeffs->ratio < 0) {
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for (size_t i = 0; i < n_in_samples; i++) {
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// DF-II
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const float z0 = x[i] + coeffs->ma1 * state->z1 + coeffs->ma2 * state->z2 + coeffs->ma3 * state->z3 + coeffs->ma4 * state->z4;
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if (!state->i) {
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state->i = -coeffs->ratio;
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y[n] = coeffs->b0 * (z0 + state->z4 + 4.f * (state->z1 + state->z3) + 6.f * state->z2);
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n++;
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}
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state->i--;
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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 (size_t i = 0; i < n_in_samples; i++) {
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// TDF-II
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const float in = coeffs->ratio * x[i];
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const float v0 = coeffs->b0 * in;
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const float v1 = 4.f * v0;
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const float v2 = 6.f * v0;
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float o = v0 + state->z1;
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state->z1 = v1 + coeffs->ma1 * o + state->z2;
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state->z2 = v2 + coeffs->ma2 * o + state->z3;
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state->z3 = v1 + coeffs->ma3 * o + state->z4;
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state->z4 = v0 + coeffs->ma4 * o;
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y[n] = o;
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n++;
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for (int j = 1; j < coeffs->ratio; j++) {
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o = state->z1;
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state->z1 = coeffs->ma1 * o + state->z2;
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state->z2 = coeffs->ma2 * o + state->z3;
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state->z3 = coeffs->ma3 * o + state->z4;
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state->z4 = coeffs->ma4 * o;
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y[n] = o;
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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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static inline void bw_src_int_process_multi(const bw_src_int_coeffs *BW_RESTRICT coeffs, bw_src_int_state *BW_RESTRICT const *BW_RESTRICT state, const float * const *BW_RESTRICT x, float *BW_RESTRICT const *BW_RESTRICT y, size_t *BW_RESTRICT n, size_t n_channels, size_t n_in_samples) {
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if (n != NULL)
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for (size_t i = 0; i < n_channels; i++)
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n[i] = bw_src_int_process(coeffs, state[i], x[i], y[i], n_in_samples);
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else
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for (size_t i = 0; i < n_channels; i++)
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bw_src_int_process(coeffs, state[i], x[i], y[i], n_in_samples);
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}
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#ifdef __cplusplus
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}
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#include <array>
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namespace Brickworks {
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/*** Public C++ API ***/
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/*! api_cpp {{{
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* ##### Brickworks::SRCInt
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* ```>>> */
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template<size_t N_CHANNELS>
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class SRCInt {
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public:
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SRCInt(int ratio);
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void reset(float x_0 = 0.f);
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std::array<size_t, N_CHANNELS> process(
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const float * const *x,
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float * const *y,
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size_t nInSamples);
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std::array<size_t, N_CHANNELS> process(
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std::array<const float *, N_CHANNELS> x,
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std::array<float *, N_CHANNELS> y,
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size_t nInSamples);
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/*! <<<...
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* }
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* ```
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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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private:
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bw_src_int_coeffs coeffs;
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bw_src_int_state states[N_CHANNELS];
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bw_src_int_state *BW_RESTRICT statesP[N_CHANNELS];
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};
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template<size_t N_CHANNELS>
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inline SRCInt<N_CHANNELS>::SRCInt(int ratio) {
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bw_src_int_init(&coeffs, ratio);
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for (size_t i = 0; i < N_CHANNELS; i++)
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statesP[i] = states + i;
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}
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template<size_t N_CHANNELS>
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inline void SRCInt<N_CHANNELS>::reset(float x_0) {
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for (size_t i = 0; i < N_CHANNELS; i++)
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bw_src_int_reset_state(&coeffs, states + i, x_0);
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}
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template<size_t N_CHANNELS>
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inline std::array<size_t, N_CHANNELS> SRCInt<N_CHANNELS>::process(
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const float * const *x,
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float * const *y,
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size_t nInSamples) {
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std::array<size_t, N_CHANNELS> ret;
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bw_src_int_process_multi(&coeffs, statesP, x, y, ret.data(), N_CHANNELS, nInSamples);
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return ret;
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}
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template<size_t N_CHANNELS>
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inline std::array<size_t, N_CHANNELS> SRCInt<N_CHANNELS>::process(
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std::array<const float *, N_CHANNELS> x,
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std::array<float *, N_CHANNELS> y,
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size_t nInSamples) {
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return process(x.data(), y.data(), nInSamples);
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}
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}
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#endif
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#endif
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