FFmpeg coverage


Directory: ../../../ffmpeg/
File: src/libavcodec/iirfilter.c
Date: 2021-09-23 20:34:37
Exec Total Coverage
Lines: 70 115 60.9%
Branches: 26 73 35.6%

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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 11 }
336