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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 | */ | ||
37 | typedef struct FFIIRFilterCoeffs { | ||
38 | int order; | ||
39 | float gain; | ||
40 | int *cx; | ||
41 | float *cy; | ||
42 | } FFIIRFilterCoeffs; | ||
43 | |||
44 | /** | ||
45 | * IIR filter state | ||
46 | */ | ||
47 | typedef struct FFIIRFilterState { | ||
48 | float x[1]; | ||
49 | } FFIIRFilterState; | ||
50 | |||
51 | /// maximum supported filter order | ||
52 | #define MAXORDER 30 | ||
53 | |||
54 | 1 | static 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 |
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1 | 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 |
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1 | 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 | 1 | wa = 2 * tan(M_PI * 0.5 * cutoff_ratio); | |
76 | |||
77 | 1 | c->cx[0] = 1; | |
78 |
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3 | for (i = 1; i < (order >> 1) + 1; i++) |
79 | 2 | c->cx[i] = c->cx[i - 1] * (order - i + 1LL) / i; | |
80 | |||
81 | 1 | p[0][0] = 1.0; | |
82 | 1 | p[0][1] = 0.0; | |
83 |
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5 | for (i = 1; i <= order; i++) |
84 | 4 | p[i][0] = p[i][1] = 0.0; | |
85 |
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5 | for (i = 0; i < order; i++) { |
86 | double zp[2]; | ||
87 | 4 | double th = (i + (order >> 1) + 0.5) * M_PI / order; | |
88 | double a_re, a_im, c_re, c_im; | ||
89 | 4 | zp[0] = cos(th) * wa; | |
90 | 4 | zp[1] = sin(th) * wa; | |
91 | 4 | a_re = zp[0] + 2.0; | |
92 | 4 | c_re = zp[0] - 2.0; | |
93 | 4 | a_im = | |
94 | 4 | c_im = zp[1]; | |
95 | 4 | zp[0] = (a_re * c_re + a_im * c_im) / (c_re * c_re + c_im * c_im); | |
96 | 4 | zp[1] = (a_im * c_re - a_re * c_im) / (c_re * c_re + c_im * c_im); | |
97 | |||
98 |
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20 | for (j = order; j >= 1; j--) { |
99 | 16 | a_re = p[j][0]; | |
100 | 16 | a_im = p[j][1]; | |
101 | 16 | p[j][0] = a_re * zp[0] - a_im * zp[1] + p[j - 1][0]; | |
102 | 16 | p[j][1] = a_re * zp[1] + a_im * zp[0] + p[j - 1][1]; | |
103 | } | ||
104 | 4 | a_re = p[0][0] * zp[0] - p[0][1] * zp[1]; | |
105 | 4 | p[0][1] = p[0][0] * zp[1] + p[0][1] * zp[0]; | |
106 | 4 | p[0][0] = a_re; | |
107 | } | ||
108 | 1 | c->gain = p[order][0]; | |
109 |
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5 | for (i = 0; i < order; i++) { |
110 | 4 | c->gain += p[i][0]; | |
111 | 4 | c->cy[i] = (-p[i][0] * p[order][0] + -p[i][1] * p[order][1]) / | |
112 | 4 | (p[order][0] * p[order][0] + p[order][1] * p[order][1]); | |
113 | } | ||
114 | 1 | c->gain /= 1 << order; | |
115 | |||
116 | 1 | return 0; | |
117 | } | ||
118 | |||
119 | ✗ | static 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 | |||
162 | 1 | av_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 | 1 | int ret = 0; | |
170 | |||
171 |
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1 | if (order <= 0 || order > MAXORDER || cutoff_ratio >= 1.0) |
172 | ✗ | return NULL; | |
173 | |||
174 |
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1 | if (!(c = av_mallocz(sizeof(*c))) || |
175 |
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1 | !(c->cx = av_malloc (sizeof(c->cx[0]) * ((order >> 1) + 1))) || |
176 |
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1 | !(c->cy = av_malloc (sizeof(c->cy[0]) * order))) |
177 | ✗ | goto free; | |
178 | 1 | c->order = order; | |
179 | |||
180 |
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1 | switch (filt_type) { |
181 | 1 | case FF_FILTER_TYPE_BUTTERWORTH: | |
182 | 1 | ret = butterworth_init_coeffs(avc, c, filt_mode, order, cutoff_ratio, | |
183 | stopband); | ||
184 | 1 | break; | |
185 | ✗ | case FF_FILTER_TYPE_BIQUAD: | |
186 | ✗ | ret = biquad_init_coeffs(avc, c, filt_mode, order, cutoff_ratio, | |
187 | stopband); | ||
188 | ✗ | break; | |
189 | ✗ | default: | |
190 | ✗ | av_log(avc, AV_LOG_ERROR, "filter type is not currently implemented\n"); | |
191 | ✗ | goto free; | |
192 | } | ||
193 | |||
194 |
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1 | if (!ret) |
195 | 1 | return c; | |
196 | ✗ | free: | |
197 | ✗ | ff_iir_filter_free_coeffsp(&c); | |
198 | ✗ | return NULL; | |
199 | } | ||
200 | |||
201 | 1 | av_cold struct FFIIRFilterState *ff_iir_filter_init_state(int order) | |
202 | { | ||
203 | 1 | FFIIRFilterState *s = av_mallocz(sizeof(FFIIRFilterState) + sizeof(s->x[0]) * (order - 1)); | |
204 | 1 | return s; | |
205 | } | ||
206 | |||
207 | #define CONV_S16(dest, source) dest = av_clip_int16(lrintf(source)); | ||
208 | |||
209 | #define CONV_FLT(dest, source) dest = source; | ||
210 | |||
211 | #define FILTER_BW_O4_1(i0, i1, i2, i3, fmt) \ | ||
212 | in = *src0 * c->gain + \ | ||
213 | c->cy[0] * s->x[i0] + \ | ||
214 | c->cy[1] * s->x[i1] + \ | ||
215 | c->cy[2] * s->x[i2] + \ | ||
216 | c->cy[3] * s->x[i3]; \ | ||
217 | res = (s->x[i0] + in) * 1 + \ | ||
218 | (s->x[i1] + s->x[i3]) * 4 + \ | ||
219 | s->x[i2] * 6; \ | ||
220 | CONV_ ## fmt(*dst0, res) \ | ||
221 | s->x[i0] = in; \ | ||
222 | src0 += sstep; \ | ||
223 | dst0 += dstep; | ||
224 | |||
225 | #define FILTER_BW_O4(type, fmt) { \ | ||
226 | int i; \ | ||
227 | const type *src0 = src; \ | ||
228 | type *dst0 = dst; \ | ||
229 | for (i = 0; i < size; i += 4) { \ | ||
230 | float in, res; \ | ||
231 | FILTER_BW_O4_1(0, 1, 2, 3, fmt); \ | ||
232 | FILTER_BW_O4_1(1, 2, 3, 0, fmt); \ | ||
233 | FILTER_BW_O4_1(2, 3, 0, 1, fmt); \ | ||
234 | FILTER_BW_O4_1(3, 0, 1, 2, fmt); \ | ||
235 | } \ | ||
236 | } | ||
237 | |||
238 | #define FILTER_DIRECT_FORM_II(type, fmt) { \ | ||
239 | int i; \ | ||
240 | const type *src0 = src; \ | ||
241 | type *dst0 = dst; \ | ||
242 | for (i = 0; i < size; i++) { \ | ||
243 | int j; \ | ||
244 | float in, res; \ | ||
245 | in = *src0 * c->gain; \ | ||
246 | for (j = 0; j < c->order; j++) \ | ||
247 | in += c->cy[j] * s->x[j]; \ | ||
248 | res = s->x[0] + in + s->x[c->order >> 1] * c->cx[c->order >> 1]; \ | ||
249 | for (j = 1; j < c->order >> 1; j++) \ | ||
250 | res += (s->x[j] + s->x[c->order - j]) * c->cx[j]; \ | ||
251 | for (j = 0; j < c->order - 1; j++) \ | ||
252 | s->x[j] = s->x[j + 1]; \ | ||
253 | CONV_ ## fmt(*dst0, res) \ | ||
254 | s->x[c->order - 1] = in; \ | ||
255 | src0 += sstep; \ | ||
256 | dst0 += dstep; \ | ||
257 | } \ | ||
258 | } | ||
259 | |||
260 | #define FILTER_O2(type, fmt) { \ | ||
261 | int i; \ | ||
262 | const type *src0 = src; \ | ||
263 | type *dst0 = dst; \ | ||
264 | for (i = 0; i < size; i++) { \ | ||
265 | float in = *src0 * c->gain + \ | ||
266 | s->x[0] * c->cy[0] + \ | ||
267 | s->x[1] * c->cy[1]; \ | ||
268 | CONV_ ## fmt(*dst0, s->x[0] + in + s->x[1] * c->cx[1]) \ | ||
269 | s->x[0] = s->x[1]; \ | ||
270 | s->x[1] = in; \ | ||
271 | src0 += sstep; \ | ||
272 | dst0 += dstep; \ | ||
273 | } \ | ||
274 | } | ||
275 | |||
276 | 1 | void ff_iir_filter(const struct FFIIRFilterCoeffs *c, | |
277 | struct FFIIRFilterState *s, int size, | ||
278 | const int16_t *src, ptrdiff_t sstep, | ||
279 | int16_t *dst, ptrdiff_t dstep) | ||
280 | { | ||
281 |
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1 | if (c->order == 2) { |
282 | ✗ | FILTER_O2(int16_t, S16) | |
283 |
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1 | } else if (c->order == 4) { |
284 |
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257 | FILTER_BW_O4(int16_t, S16) |
285 | } else { | ||
286 | ✗ | FILTER_DIRECT_FORM_II(int16_t, S16) | |
287 | } | ||
288 | 1 | } | |
289 | |||
290 | /** | ||
291 | * Perform IIR filtering on floating-point input samples. | ||
292 | * | ||
293 | * @param coeffs pointer to filter coefficients | ||
294 | * @param state pointer to filter state | ||
295 | * @param size input length | ||
296 | * @param src source samples | ||
297 | * @param sstep source stride | ||
298 | * @param dst filtered samples (destination may be the same as input) | ||
299 | * @param dstep destination stride | ||
300 | */ | ||
301 | ✗ | static void iir_filter_flt(const struct FFIIRFilterCoeffs *c, | |
302 | struct FFIIRFilterState *s, int size, | ||
303 | const float *src, ptrdiff_t sstep, | ||
304 | float *dst, ptrdiff_t dstep) | ||
305 | { | ||
306 | ✗ | if (c->order == 2) { | |
307 | ✗ | FILTER_O2(float, FLT) | |
308 | ✗ | } else if (c->order == 4) { | |
309 | ✗ | FILTER_BW_O4(float, FLT) | |
310 | } else { | ||
311 | ✗ | FILTER_DIRECT_FORM_II(float, FLT) | |
312 | } | ||
313 | } | ||
314 | |||
315 | 1 | av_cold void ff_iir_filter_free_statep(struct FFIIRFilterState **state) | |
316 | { | ||
317 | 1 | av_freep(state); | |
318 | 1 | } | |
319 | |||
320 | 12 | av_cold void ff_iir_filter_free_coeffsp(struct FFIIRFilterCoeffs **coeffsp) | |
321 | { | ||
322 | 12 | struct FFIIRFilterCoeffs *coeffs = *coeffsp; | |
323 |
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12 | if (coeffs) { |
324 | 1 | av_freep(&coeffs->cx); | |
325 | 1 | av_freep(&coeffs->cy); | |
326 | } | ||
327 | 12 | av_freep(coeffsp); | |
328 | 12 | } | |
329 | |||
330 | 11 | void ff_iir_filter_init(FFIIRFilterContext *f) { | |
331 | 11 | f->filter_flt = iir_filter_flt; | |
332 | |||
333 | #if HAVE_MIPSFPU | ||
334 | ff_iir_filter_init_mips(f); | ||
335 | #endif | ||
336 | 11 | } | |
337 |