236 lines
7.8 KiB
C
236 lines
7.8 KiB
C
/*
|
|
* Brickworks
|
|
*
|
|
* Copyright (C) 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 {{{ 0.6.0 }}}
|
|
* requires {{{ bw_common bw_math }}}
|
|
* description {{{
|
|
* Integer-ratio IIR sample rate converter.
|
|
*
|
|
* Multi-rate filtering inspired by
|
|
*
|
|
* M. Holters and J.Parker, "A Combined Model for a Bucket Brigade Device and
|
|
* its Input and Output Filters", 21st Intl. Conf. Digital Audio Effects
|
|
* (DAFx-18), Aveiro, Portugal, September 2018.
|
|
* }}}
|
|
* changelog {{{
|
|
* <ul>
|
|
* <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_src_int_process_multi()</code>.</li>
|
|
* <li>Added C++ wrapper.</li>
|
|
* </ul>
|
|
* </li>
|
|
* <li>Version <strong>0.4.0</strong>:
|
|
* <ul>
|
|
* <li>First release.</li>
|
|
* </ul>
|
|
* </li>
|
|
* </ul>
|
|
* }}}
|
|
*/
|
|
|
|
#ifndef _BW_SRC_INT_H
|
|
#define _BW_SRC_INT_H
|
|
|
|
#ifdef __cplusplus
|
|
extern "C" {
|
|
#endif
|
|
|
|
#include <bw_common.h>
|
|
|
|
/*! api {{{
|
|
* #### bw_src_int_coeffs
|
|
* ```>>> */
|
|
typedef struct _bw_src_int_coeffs bw_src_int_coeffs;
|
|
/*! <<<```
|
|
* Coefficients and related.
|
|
*
|
|
* #### bw_src_int_state
|
|
* ```>>> */
|
|
typedef struct _bw_src_int_state bw_src_int_state;
|
|
/*! <<<```
|
|
* Internal state and related.
|
|
*
|
|
* #### bw_src_int_init()
|
|
* ```>>> */
|
|
static inline void bw_src_int_init(bw_src_int_coeffs *BW_RESTRICT coeffs, int ratio);
|
|
/*! <<<```
|
|
* Initializes `coeffs` using the given resampling `ratio`.
|
|
*
|
|
* If `ratio` is positive, then the sample rate of the output signal will be
|
|
* `ratio` times the sample rate of the input signal, otherwise, if it is
|
|
* negative, then the sample rate of the output signal will be equal to the
|
|
* sample rate of the input signal divided by `-ratio`. `ratio` *MUST NOT* be
|
|
* in [`-1`, `1`].
|
|
*
|
|
* #### bw_src_int_reset_state()
|
|
* ```>>> */
|
|
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);
|
|
/*! <<<```
|
|
* Resets the given `state` to its initial values using the given `coeffs`
|
|
* and the quiescent/initial input value `x0`.
|
|
*
|
|
* #### bw_src_int_process()
|
|
* ```>>> */
|
|
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);
|
|
/*! <<<```
|
|
* Processes the first `n_in_samples` of the input buffer `x` and fills the
|
|
* output buffer `y` using `coeffs`, while using and updating `state`.
|
|
*
|
|
* The number of generated output samples will be `ratio` times
|
|
* `n_in_samples` if `ratio` is positive, otherwise at most `n_in_samples`
|
|
* divided by `-ratio` and then rounded towards positive infinity.
|
|
*
|
|
* Returns the number of generated output samples.
|
|
*
|
|
* #### bw_src_int_process_multi()
|
|
* ```>>> */
|
|
static inline void bw_src_int_process_multi(const bw_src_int_coeffs *BW_RESTRICT coeffs, bw_src_int_state **BW_RESTRICT state, const float **x, float **y, int *n, int n_channels, int n_in_samples);
|
|
/*! <<<```
|
|
* Processes the first `n_in_samples` of the `n_channels` input buffers `x`
|
|
* and fills the `n_channels` output buffers `y` using `coeffs`, while using
|
|
* and updating each of the `n_channels` `state`s.
|
|
*
|
|
* The number of generated output samples in each output buffer will be
|
|
* `ratio` times `n_in_samples` if `ratio` is positive, otherwise at most
|
|
* `n_in_samples` divided by `-ratio` and then rounded towards positive
|
|
* infinity.
|
|
*
|
|
* `n` is filled with the number of generated output samples for each output
|
|
* buffer, if not `NULL`.
|
|
* }}} */
|
|
|
|
/*** 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_src_int_coeffs {
|
|
int ratio;
|
|
float a1;
|
|
float a2;
|
|
float a3;
|
|
float a4;
|
|
float b0;
|
|
float b1;
|
|
float b2;
|
|
};
|
|
|
|
struct _bw_src_int_state {
|
|
int i;
|
|
float z1;
|
|
float z2;
|
|
float z3;
|
|
float z4;
|
|
};
|
|
|
|
static inline void bw_src_int_init(bw_src_int_coeffs *BW_RESTRICT coeffs, int ratio) {
|
|
coeffs->ratio = ratio;
|
|
// 4th-degree Butterworth with cutoff at ratio * Nyquist, using bilinear transform w/ prewarping
|
|
const float fc = (float)(ratio >= 0 ? ratio : -ratio);
|
|
const float T = bw_tanf_3(1.570796326794896f / fc);
|
|
const float T2 = T * T;
|
|
const float k = 1.f / (T * (T * (T * (T + 2.613125929752753f) + 3.414213562373095f) + 2.613125929752753f) + 1.f);
|
|
coeffs->b0 = k * T2 * T2;
|
|
coeffs->b1 = 4.f * coeffs->b0;
|
|
coeffs->b2 = 6.f * coeffs->b0;
|
|
coeffs->a1 = k * (T * (T2 * (4.f * T + 5.226251859505504f) - 5.226251859505504f) - 4.f);
|
|
coeffs->a2 = k * (T2 * (6.f * T2 - 6.82842712474619f) + 6.f);
|
|
coeffs->a3 = k * (T * (T2 * (4.f * T - 5.226251859505504f) + 5.226251859505504f) - 4.f);
|
|
coeffs->a4 = k * (T * (T * (T * (T - 2.613125929752753f) + 3.414213562373095f) - 2.613125929752753f) + 1.f);
|
|
}
|
|
|
|
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) {
|
|
if (coeffs->ratio < 0) {
|
|
// DF-II
|
|
state->z1 = x0 / (1.f + coeffs->a1 + coeffs->a2 + coeffs->a3 + coeffs->a4);
|
|
state->z2 = state->z1;
|
|
state->z3 = state->z2;
|
|
state->z4 = state->z3;
|
|
state->i = 0;
|
|
} else {
|
|
// TDF-II
|
|
state->z4 = (coeffs->b0 - coeffs->a4) * x0;
|
|
state->z3 = (coeffs->b1 - coeffs->a3) * x0 + state->z4;
|
|
state->z2 = (coeffs->b2 - coeffs->a2) * x0 + state->z3;
|
|
state->z1 = (coeffs->b1 - coeffs->a1) * x0 + state->z2;
|
|
}
|
|
}
|
|
|
|
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) {
|
|
int n = 0;
|
|
if (coeffs->ratio < 0) {
|
|
for (int i = 0; i < n_in_samples; i++) {
|
|
// DF-II
|
|
const float z0 = x[i] - coeffs->a1 * state->z1 - coeffs->a2 * state->z2 - coeffs->a3 * state->z3 - coeffs->a4 * state->z4;
|
|
if (!state->i) {
|
|
state->i = -coeffs->ratio;
|
|
y[n] = coeffs->b0 * (z0 + state->z4) + coeffs->b1 * (state->z1 + state->z3) + coeffs->b2 * state->z2;
|
|
n++;
|
|
}
|
|
state->i--;
|
|
state->z4 = state->z3;
|
|
state->z3 = state->z2;
|
|
state->z2 = state->z1;
|
|
state->z1 = z0;
|
|
}
|
|
} else {
|
|
for (int i = 0; i < n_in_samples; i++) {
|
|
// TDF-II
|
|
const float v0 = coeffs->b0 * x[i];
|
|
const float v1 = coeffs->b1 * x[i];
|
|
const float v2 = coeffs->b2 * x[i];
|
|
for (int j = 0; j < coeffs->ratio; j++) {
|
|
y[n] = v0 + state->z1;
|
|
state->z1 = v1 - coeffs->a1 * y[n] + state->z2;
|
|
state->z2 = v2 - coeffs->a2 * y[n] + state->z3;
|
|
state->z3 = v1 - coeffs->a3 * y[n] + state->z4;
|
|
state->z4 = v0 - coeffs->a4 * y[n];
|
|
n++;
|
|
}
|
|
}
|
|
}
|
|
return n;
|
|
}
|
|
|
|
static inline void bw_src_int_process_multi(const bw_src_int_coeffs *BW_RESTRICT coeffs, bw_src_int_state **BW_RESTRICT state, const float **x, float **y, int *n, int n_channels, int n_in_samples) {
|
|
if (n != NULL)
|
|
for (int i = 0; i < n_channels; i++)
|
|
n[i] = bw_src_int_process(coeffs, state[i], x[i], y[i], n_in_samples);
|
|
else
|
|
for (int i = 0; i < n_channels; i++)
|
|
bw_src_int_process(coeffs, state[i], x[i], y[i], n_in_samples);
|
|
}
|
|
|
|
#ifdef __cplusplus
|
|
}
|
|
#endif
|
|
|
|
#endif
|