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https://github.com/libretro/RetroArch
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Rewrite IIR DSP filter.
This commit is contained in:
Themaister
parent
7aaa0c254f
commit
d2161dfa50
8
audio/filters/IIR.dsp
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8
audio/filters/IIR.dsp
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filters = 1
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filter0 = iir
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iir_frequency = 1024.0
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iir_quality = 0.707
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iir_gain = 0.0
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iir_type = LPF
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360
audio/filters/iir.c
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360
audio/filters/iir.c
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/* RetroArch - A frontend for libretro.
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* Copyright (C) 2010-2014 - Hans-Kristian Arntzen
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* Copyright (C) 2014 - Brad Miller
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*
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* RetroArch is free software: you can redistribute it and/or modify it under the terms
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* of the GNU General Public License as published by the Free Software Found-
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* ation, either version 3 of the License, or (at your option) any later version.
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*
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* RetroArch is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
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* without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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* PURPOSE. See the 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 along with RetroArch.
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* If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "dspfilter.h"
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#include <math.h>
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#include <stdlib.h>
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#include <string.h>
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#ifndef M_PI
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#define M_PI 3.1415926535897932384626433832795
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#endif
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#define sqr(a) ((a) * (a))
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/* filter types */
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enum IIRFilter {
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LPF, /* low pass filter */
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HPF, /* High pass filter */
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BPCSGF,/* band pass filter 1 */
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BPZPGF,/* band pass filter 2 */
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APF, /* Allpass filter*/
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NOTCH, /* Notch Filter */
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RIAA_phono, /* RIAA record/tape deemphasis */
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PEQ, /* Peaking band EQ filter */
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BBOOST, /* Bassboost filter */
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LSH, /* Low shelf filter */
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HSH, /* High shelf filter */
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RIAA_CD /* CD de-emphasis */
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};
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struct iir_data
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{
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float b0, b1, b2;
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float a0, a1, a2;
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struct
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{
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float xn1, xn2;
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float yn1, yn2;
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} l, r;
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};
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static void iir_free(void *data)
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{
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free(data);
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}
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static void iir_process(void *data, struct dspfilter_output *output,
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const struct dspfilter_input *input)
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{
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unsigned i;
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struct iir_data *iir = (struct iir_data*)data;
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output->samples = input->samples;
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output->frames = input->frames;
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float *out = output->samples;
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float b0 = iir->b0;
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float b1 = iir->b1;
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float b2 = iir->b2;
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float a0 = iir->a0;
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float a1 = iir->a1;
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float a2 = iir->a2;
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float xn1_l = iir->l.xn1;
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float xn2_l = iir->l.xn2;
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float yn1_l = iir->l.yn1;
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float yn2_l = iir->l.yn2;
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float xn1_r = iir->r.xn1;
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float xn2_r = iir->r.xn2;
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float yn1_r = iir->r.yn1;
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float yn2_r = iir->r.yn2;
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for (i = 0; i < input->frames; i++, out += 2)
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{
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float in_l = out[0];
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float in_r = out[1];
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float l = (b0 * in_l + b1 * xn1_l + b2 * xn2_l - a1 * yn1_l - a2 * yn2_l) / a0;
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float r = (b0 * in_r + b1 * xn1_r + b2 * xn2_r - a1 * yn1_r - a2 * yn2_r) / a0;
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xn2_l = xn1_l;
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xn1_l = in_l;
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yn2_l = yn1_l;
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yn1_l = l;
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xn2_r = xn1_r;
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xn1_r = in_r;
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yn2_r = yn1_r;
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yn1_r = r;
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out[0] = l;
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out[1] = r;
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}
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iir->l.xn1 = xn1_l;
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iir->l.xn2 = xn2_l;
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iir->l.yn1 = yn1_l;
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iir->l.yn2 = yn2_l;
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iir->r.xn1 = xn1_r;
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iir->r.xn2 = xn2_r;
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iir->r.yn1 = yn1_r;
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iir->r.yn2 = yn2_r;
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}
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#define CHECK(x) if (!strcmp(str, #x)) return x
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static enum IIRFilter str_to_type(const char *str)
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{
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CHECK(LPF);
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CHECK(HPF);
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CHECK(BPCSGF);
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CHECK(BPZPGF);
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CHECK(APF);
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CHECK(NOTCH);
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CHECK(RIAA_phono);
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CHECK(PEQ);
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CHECK(BBOOST);
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CHECK(LSH);
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CHECK(HSH);
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CHECK(RIAA_CD);
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return LPF; // Fallback.
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}
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static void make_poly_from_roots(
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const double *roots, unsigned num_roots, float *poly)
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{
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unsigned i, j;
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poly[0] = 1;
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poly[1] = -roots[0];
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memset(poly + 2, 0, (num_roots + 1 - 2) * sizeof(*poly));
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for (i = 1; i < num_roots; i++)
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for (j = num_roots; j > 0; j--)
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poly[j] -= poly[j - 1] * roots[i];
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}
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static void iir_filter_init(struct iir_data *iir,
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float sample_rate, float freq, float qual, float gain, enum IIRFilter filter_type)
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{
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double omega = 2.0 * M_PI * freq / sample_rate;
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double cs = cos(omega);
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double sn = sin(omega);
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double a1pha = sn / (2.0 * qual);
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double A = exp(log(10.0) * gain / 40.0);
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double beta = sqrt(A + A);
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float b0 = 0.0, b1 = 0.0, b2 = 0.0, a0 = 0.0, a1 = 0.0, a2 = 0.0;
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// Set up filter coefficients according to type
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switch (filter_type)
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{
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case LPF:
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b0 = (1.0 - cs) / 2.0;
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b1 = 1.0 - cs ;
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b2 = (1.0 - cs) / 2.0;
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a0 = 1.0 + a1pha;
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a1 = -2.0 * cs;
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a2 = 1.0 - a1pha;
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break;
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case HPF:
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b0 = (1.0 + cs) / 2.0;
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b1 = -(1.0 + cs);
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b2 = (1.0 + cs) / 2.0;
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a0 = 1.0 + a1pha;
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a1 = -2.0 * cs;
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a2 = 1.0 - a1pha;
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break;
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case APF:
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b0 = 1.0 - a1pha;
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b1 = -2.0 * cs;
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b2 = 1.0 + a1pha;
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a0 = 1.0 + a1pha;
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a1 = -2.0 * cs;
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a2 = 1.0 - a1pha;
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break;
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case BPZPGF:
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b0 = a1pha;
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b1 = 0.0;
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b2 = -a1pha;
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a0 = 1.0 + a1pha;
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a1 = -2.0 * cs;
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a2 = 1.0 - a1pha;
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break;
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case BPCSGF:
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b0 = sn / 2.0;
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b1 = 0.0;
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b2 = -sn / 2.0;
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a0 = 1.0 + a1pha;
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a1 = -2.0 * cs;
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a2 = 1.0 - a1pha;
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break;
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case NOTCH:
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b0 = 1.0;
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b1 = -2.0 * cs;
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b2 = 1.0;
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a0 = 1.0 + a1pha;
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a1 = -2.0 * cs;
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a2 = 1.0 - a1pha;
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break;
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case RIAA_phono: /* http://www.dsprelated.com/showmessage/73300/3.php */
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{
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float b[3], a[3];
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if ((int)sample_rate == 44100)
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{
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static const double zeros[] = {-0.2014898, 0.9233820};
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static const double poles[] = {0.7083149, 0.9924091};
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make_poly_from_roots(zeros, 2, b);
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make_poly_from_roots(poles, 2, a);
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}
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else if ((int)sample_rate == 48000)
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{
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static const double zeros[] = {-0.1766069, 0.9321590};
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static const double poles[] = {0.7396325, 0.9931330};
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make_poly_from_roots(zeros, 2, b);
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make_poly_from_roots(poles, 2, a);
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}
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else if ((int)sample_rate == 88200)
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{
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static const double zeros[] = {-0.1168735, 0.9648312};
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static const double poles[] = {0.8590646, 0.9964002};
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make_poly_from_roots(zeros, 2, b);
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make_poly_from_roots(poles, 2, a);
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}
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else if ((int)sample_rate == 96000)
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{
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static const double zeros[] = {-0.1141486, 0.9676817};
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static const double poles[] = {0.8699137, 0.9966946};
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make_poly_from_roots(zeros, 2, b);
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make_poly_from_roots(poles, 2, a);
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}
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b0 = b[0];
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b1 = b[1];
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b2 = b[2];
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a0 = a[0];
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a1 = a[1];
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a2 = a[2];
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/* Normalise to 0dB at 1kHz (Thanks to Glenn Davis) */
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double y = 2.0 * M_PI * 1000.0 / sample_rate;
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double b_re = b0 + b1 * cos(-y) + b2 * cos(-2.0 * y);
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double a_re = a0 + a1 * cos(-y) + a2 * cos(-2.0 * y);
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double b_im = b1 * sin(-y) + b2 * sin(-2.0 * y);
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double a_im = a1 * sin(-y) + a2 * sin(-2.0 * y);
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double g = 1.0 / sqrt((sqr(b_re) + sqr(b_im)) / (sqr(a_re) + sqr(a_im)));
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b0 *= g; b1 *= g; b2 *= g;
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break;
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}
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case PEQ:
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b0 = 1.0 + a1pha * A;
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b1 = -2.0 * cs;
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b2 = 1.0 - a1pha * A;
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a0 = 1.0 + a1pha / A;
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a1 = -2.0 * cs;
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a2 = 1.0 - a1pha / A;
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break;
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case BBOOST:
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beta = sqrt((A * A + 1) / 1.0 - (pow((A - 1), 2)));
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b0 = A * ((A + 1) - (A - 1) * cs + beta * sn);
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b1 = 2 * A * ((A - 1) - (A + 1) * cs);
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b2 = A * ((A + 1) - (A - 1) * cs - beta * sn);
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a0 = ((A + 1) + (A - 1) * cs + beta * sn);
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a1 = -2 * ((A - 1) + (A + 1) * cs);
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a2 = (A + 1) + (A - 1) * cs - beta * sn;
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break;
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case LSH:
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b0 = A * ((A + 1) - (A - 1) * cs + beta * sn);
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b1 = 2 * A * ((A - 1) - (A + 1) * cs);
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b2 = A * ((A + 1) - (A - 1) * cs - beta * sn);
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a0 = (A + 1) + (A - 1) * cs + beta * sn;
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a1 = -2 * ((A - 1) + (A + 1) * cs);
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a2 = (A + 1) + (A - 1) * cs - beta * sn;
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break;
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case RIAA_CD:
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omega = 2.0 * M_PI * 5283.0 / sample_rate;
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cs = cos(omega);
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sn = sin(omega);
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a1pha = sn / (2.0 * 0.4845);
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A = exp(log(10.0) * -9.477 / 40.0);
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beta = sqrt(A + A);
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case HSH:
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b0 = A * ((A + 1.0) + (A - 1.0) * cs + beta * sn);
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b1 = -2.0 * A * ((A - 1.0) + (A + 1.0) * cs);
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b2 = A * ((A + 1.0) + (A - 1.0) * cs - beta * sn);
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a0 = (A + 1.0) - (A - 1.0) * cs + beta * sn;
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a1 = 2.0 * ((A - 1.0) - (A + 1.0) * cs);
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a2 = (A + 1.0) - (A - 1.0) * cs - beta * sn;
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break;
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default:
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break;
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}
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iir->b0 = b0;
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iir->b1 = b1;
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iir->b2 = b2;
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iir->a0 = a0;
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iir->a1 = a1;
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iir->a2 = a2;
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}
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static void *iir_init(const struct dspfilter_info *info,
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const struct dspfilter_config *config, void *userdata)
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{
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struct iir_data *iir = (struct iir_data*)calloc(1, sizeof(*iir));
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if (!iir)
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return NULL;
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float freq, qual, gain;
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config->get_float(userdata, "frequency", &freq, 1024.0f);
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config->get_float(userdata, "quality", &qual, 0.707f);
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config->get_float(userdata, "gain", &gain, 0.0f);
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char *type = NULL;
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config->get_string(userdata, "type", &type, "LPF");
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enum IIRFilter filter = str_to_type(type);
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config->free(type);
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iir_filter_init(iir, info->input_rate, freq, qual, gain, filter);
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return iir;
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}
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static const struct dspfilter_implementation iir_plug = {
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iir_init,
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iir_process,
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iir_free,
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DSPFILTER_API_VERSION,
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"IIR",
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"iir",
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};
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#ifdef HAVE_FILTERS_BUILTIN
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#define dspfilter_get_implementation iir_dspfilter_get_implementation
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#endif
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const struct dspfilter_implementation *dspfilter_get_implementation(dspfilter_simd_mask_t mask)
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{
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(void)mask;
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return &iir_plug;
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}
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#undef dspfilter_get_implementation
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