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1/*
2 * IIR filter
3 * Copyright (c) 2008 Konstantin Shishkov
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22/**
23 * @file
24 * different IIR filters implementation
25 */
26
27#include <math.h>
28
29#include "libavutil/attributes.h"
30#include "libavutil/common.h"
31
32#include "iirfilter.h"
33
34/**
35 * IIR filter global parameters
36 */
37typedef struct FFIIRFilterCoeffs {
38 int order;
39 float gain;
40 int *cx;
41 float *cy;
42} FFIIRFilterCoeffs;
43
44/**
45 * IIR filter state
46 */
47typedef struct FFIIRFilterState {
48 float x[1];
49} FFIIRFilterState;
50
51/// maximum supported filter order
52#define MAXORDER 30
53
54static av_cold int butterworth_init_coeffs(void *avc,
55 struct FFIIRFilterCoeffs *c,
56 enum IIRFilterMode filt_mode,
57 int order, float cutoff_ratio,
58 float stopband)
59{
60 int i, j;
61 double wa;
62 double p[MAXORDER + 1][2];
63
64 if (filt_mode != FF_FILTER_MODE_LOWPASS) {
65 av_log(avc, AV_LOG_ERROR, "Butterworth filter currently only supports "
66 "low-pass filter mode\n");
67 return -1;
68 }
69 if (order & 1) {
70 av_log(avc, AV_LOG_ERROR, "Butterworth filter currently only supports "
71 "even filter orders\n");
72 return -1;
73 }
74
75 wa = 2 * tan(M_PI * 0.5 * cutoff_ratio);
76
77 c->cx[0] = 1;
78 for (i = 1; i < (order >> 1) + 1; i++)
79 c->cx[i] = c->cx[i - 1] * (order - i + 1LL) / i;
80
81 p[0][0] = 1.0;
82 p[0][1] = 0.0;
83 for (i = 1; i <= order; i++)
84 p[i][0] = p[i][1] = 0.0;
85 for (i = 0; i < order; i++) {
86 double zp[2];
87 double th = (i + (order >> 1) + 0.5) * M_PI / order;
88 double a_re, a_im, c_re, c_im;
89 zp[0] = cos(th) * wa;
90 zp[1] = sin(th) * wa;
91 a_re = zp[0] + 2.0;
92 c_re = zp[0] - 2.0;
93 a_im =
94 c_im = zp[1];
95 zp[0] = (a_re * c_re + a_im * c_im) / (c_re * c_re + c_im * c_im);
96 zp[1] = (a_im * c_re - a_re * c_im) / (c_re * c_re + c_im * c_im);
97
98 for (j = order; j >= 1; j--) {
99 a_re = p[j][0];
100 a_im = p[j][1];
101 p[j][0] = a_re * zp[0] - a_im * zp[1] + p[j - 1][0];
102 p[j][1] = a_re * zp[1] + a_im * zp[0] + p[j - 1][1];
103 }
104 a_re = p[0][0] * zp[0] - p[0][1] * zp[1];
105 p[0][1] = p[0][0] * zp[1] + p[0][1] * zp[0];
106 p[0][0] = a_re;
107 }
108 c->gain = p[order][0];
109 for (i = 0; i < order; i++) {
110 c->gain += p[i][0];
111 c->cy[i] = (-p[i][0] * p[order][0] + -p[i][1] * p[order][1]) /
112 (p[order][0] * p[order][0] + p[order][1] * p[order][1]);
113 }
114 c->gain /= 1 << order;
115
116 return 0;
117}
118
119static av_cold int biquad_init_coeffs(void *avc, struct FFIIRFilterCoeffs *c,
120 enum IIRFilterMode filt_mode, int order,
121 float cutoff_ratio, float stopband)
122{
123 double cos_w0, sin_w0;
124 double a0, x0, x1;
125
126 if (filt_mode != FF_FILTER_MODE_HIGHPASS &&
127 filt_mode != FF_FILTER_MODE_LOWPASS) {
128 av_log(avc, AV_LOG_ERROR, "Biquad filter currently only supports "
129 "high-pass and low-pass filter modes\n");
130 return -1;
131 }
132 if (order != 2) {
133 av_log(avc, AV_LOG_ERROR, "Biquad filter must have order of 2\n");
134 return -1;
135 }
136
137 cos_w0 = cos(M_PI * cutoff_ratio);
138 sin_w0 = sin(M_PI * cutoff_ratio);
139
140 a0 = 1.0 + (sin_w0 / 2.0);
141
142 if (filt_mode == FF_FILTER_MODE_HIGHPASS) {
143 c->gain = ((1.0 + cos_w0) / 2.0) / a0;
144 x0 = ((1.0 + cos_w0) / 2.0) / a0;
145 x1 = (-(1.0 + cos_w0)) / a0;
146 } else { // FF_FILTER_MODE_LOWPASS
147 c->gain = ((1.0 - cos_w0) / 2.0) / a0;
148 x0 = ((1.0 - cos_w0) / 2.0) / a0;
149 x1 = (1.0 - cos_w0) / a0;
150 }
151 c->cy[0] = (-1.0 + (sin_w0 / 2.0)) / a0;
152 c->cy[1] = (2.0 * cos_w0) / a0;
153
154 // divide by gain to make the x coeffs integers.
155 // during filtering, the delay state will include the gain multiplication
156 c->cx[0] = lrintf(x0 / c->gain);
157 c->cx[1] = lrintf(x1 / c->gain);
158
159 return 0;
160}
161
162av_cold struct FFIIRFilterCoeffs *ff_iir_filter_init_coeffs(void *avc,
163 enum IIRFilterType filt_type,
164 enum IIRFilterMode filt_mode,
165 int order, float cutoff_ratio,
166 float stopband, float ripple)
167{
168 FFIIRFilterCoeffs *c;
169 int ret = 0;
170
171 if (order <= 0 || order > MAXORDER || cutoff_ratio >= 1.0)
172 return NULL;
173
174 FF_ALLOCZ_OR_GOTO(avc, c, sizeof(FFIIRFilterCoeffs),
175 init_fail);
176 FF_ALLOC_OR_GOTO(avc, c->cx, sizeof(c->cx[0]) * ((order >> 1) + 1),
177 init_fail);
178 FF_ALLOC_OR_GOTO(avc, c->cy, sizeof(c->cy[0]) * order,
179 init_fail);
180 c->order = order;
181
182 switch (filt_type) {
183 case FF_FILTER_TYPE_BUTTERWORTH:
184 ret = butterworth_init_coeffs(avc, c, filt_mode, order, cutoff_ratio,
185 stopband);
186 break;
187 case FF_FILTER_TYPE_BIQUAD:
188 ret = biquad_init_coeffs(avc, c, filt_mode, order, cutoff_ratio,
189 stopband);
190 break;
191 default:
192 av_log(avc, AV_LOG_ERROR, "filter type is not currently implemented\n");
193 goto init_fail;
194 }
195
196 if (!ret)
197 return c;
198
199init_fail:
200 ff_iir_filter_free_coeffsp(&c);
201 return NULL;
202}
203
204av_cold struct FFIIRFilterState *ff_iir_filter_init_state(int order)
205{
206 FFIIRFilterState *s = av_mallocz(sizeof(FFIIRFilterState) + sizeof(s->x[0]) * (order - 1));
207 return s;
208}
209
210#define CONV_S16(dest, source) dest = av_clip_int16(lrintf(source));
211
212#define CONV_FLT(dest, source) dest = source;
213
214#define FILTER_BW_O4_1(i0, i1, i2, i3, fmt) \
215 in = *src0 * c->gain + \
216 c->cy[0] * s->x[i0] + \
217 c->cy[1] * s->x[i1] + \
218 c->cy[2] * s->x[i2] + \
219 c->cy[3] * s->x[i3]; \
220 res = (s->x[i0] + in) * 1 + \
221 (s->x[i1] + s->x[i3]) * 4 + \
222 s->x[i2] * 6; \
223 CONV_ ## fmt(*dst0, res) \
224 s->x[i0] = in; \
225 src0 += sstep; \
226 dst0 += dstep;
227
228#define FILTER_BW_O4(type, fmt) { \
229 int i; \
230 const type *src0 = src; \
231 type *dst0 = dst; \
232 for (i = 0; i < size; i += 4) { \
233 float in, res; \
234 FILTER_BW_O4_1(0, 1, 2, 3, fmt); \
235 FILTER_BW_O4_1(1, 2, 3, 0, fmt); \
236 FILTER_BW_O4_1(2, 3, 0, 1, fmt); \
237 FILTER_BW_O4_1(3, 0, 1, 2, fmt); \
238 } \
239}
240
241#define FILTER_DIRECT_FORM_II(type, fmt) { \
242 int i; \
243 const type *src0 = src; \
244 type *dst0 = dst; \
245 for (i = 0; i < size; i++) { \
246 int j; \
247 float in, res; \
248 in = *src0 * c->gain; \
249 for (j = 0; j < c->order; j++) \
250 in += c->cy[j] * s->x[j]; \
251 res = s->x[0] + in + s->x[c->order >> 1] * c->cx[c->order >> 1]; \
252 for (j = 1; j < c->order >> 1; j++) \
253 res += (s->x[j] + s->x[c->order - j]) * c->cx[j]; \
254 for (j = 0; j < c->order - 1; j++) \
255 s->x[j] = s->x[j + 1]; \
256 CONV_ ## fmt(*dst0, res) \
257 s->x[c->order - 1] = in; \
258 src0 += sstep; \
259 dst0 += dstep; \
260 } \
261}
262
263#define FILTER_O2(type, fmt) { \
264 int i; \
265 const type *src0 = src; \
266 type *dst0 = dst; \
267 for (i = 0; i < size; i++) { \
268 float in = *src0 * c->gain + \
269 s->x[0] * c->cy[0] + \
270 s->x[1] * c->cy[1]; \
271 CONV_ ## fmt(*dst0, s->x[0] + in + s->x[1] * c->cx[1]) \
272 s->x[0] = s->x[1]; \
273 s->x[1] = in; \
274 src0 += sstep; \
275 dst0 += dstep; \
276 } \
277}
278
279void ff_iir_filter(const struct FFIIRFilterCoeffs *c,
280 struct FFIIRFilterState *s, int size,
281 const int16_t *src, ptrdiff_t sstep,
282 int16_t *dst, ptrdiff_t dstep)
283{
284 if (c->order == 2) {
285 FILTER_O2(int16_t, S16)
286 } else if (c->order == 4) {
287 FILTER_BW_O4(int16_t, S16)
288 } else {
289 FILTER_DIRECT_FORM_II(int16_t, S16)
290 }
291}
292
293void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *c,
294 struct FFIIRFilterState *s, int size,
295 const float *src, ptrdiff_t sstep,
296 float *dst, ptrdiff_t dstep)
297{
298 if (c->order == 2) {
299 FILTER_O2(float, FLT)
300 } else if (c->order == 4) {
301 FILTER_BW_O4(float, FLT)
302 } else {
303 FILTER_DIRECT_FORM_II(float, FLT)
304 }
305}
306
307av_cold void ff_iir_filter_free_statep(struct FFIIRFilterState **state)
308{
309 av_freep(state);
310}
311
312av_cold void ff_iir_filter_free_coeffsp(struct FFIIRFilterCoeffs **coeffsp)
313{
314 struct FFIIRFilterCoeffs *coeffs = *coeffsp;
315 if (coeffs) {
316 av_freep(&coeffs->cx);
317 av_freep(&coeffs->cy);
318 }
319 av_freep(coeffsp);
320}
321
322void ff_iir_filter_init(FFIIRFilterContext *f) {
323 f->filter_flt = ff_iir_filter_flt;
324
325 if (HAVE_MIPSFPU)
326 ff_iir_filter_init_mips(f);
327}
328
generated by cgit at 2024-05-17 03:17:49 (GMT)