c0ac9472893dc3f5d57dabb77ae21c4e990b9e86
[libav.git] / libavcodec / iirfilter.c
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 "iirfilter.h"
28 #include <math.h>
29
30 /**
31 * IIR filter global parameters
32 */
33 typedef struct FFIIRFilterCoeffs{
34 int order;
35 float gain;
36 int *cx;
37 float *cy;
38 }FFIIRFilterCoeffs;
39
40 /**
41 * IIR filter state
42 */
43 typedef struct FFIIRFilterState{
44 float x[1];
45 }FFIIRFilterState;
46
47 /// maximum supported filter order
48 #define MAXORDER 30
49
50 static int butterworth_init_coeffs(void *avc, struct FFIIRFilterCoeffs *c,
51 enum IIRFilterMode filt_mode,
52 int order, float cutoff_ratio,
53 float stopband)
54 {
55 int i, j;
56 double wa;
57 double p[MAXORDER + 1][2];
58
59 if (filt_mode != FF_FILTER_MODE_LOWPASS) {
60 av_log(avc, AV_LOG_ERROR, "Butterworth filter currently only supports "
61 "low-pass filter mode\n");
62 return -1;
63 }
64 if (order & 1) {
65 av_log(avc, AV_LOG_ERROR, "Butterworth filter currently only supports "
66 "even filter orders\n");
67 return -1;
68 }
69
70 wa = 2 * tan(M_PI * 0.5 * cutoff_ratio);
71
72 c->cx[0] = 1;
73 for(i = 1; i < (order >> 1) + 1; i++)
74 c->cx[i] = c->cx[i - 1] * (order - i + 1LL) / i;
75
76 p[0][0] = 1.0;
77 p[0][1] = 0.0;
78 for(i = 1; i <= order; i++)
79 p[i][0] = p[i][1] = 0.0;
80 for(i = 0; i < order; i++){
81 double zp[2];
82 double th = (i + (order >> 1) + 0.5) * M_PI / order;
83 double a_re, a_im, c_re, c_im;
84 zp[0] = cos(th) * wa;
85 zp[1] = sin(th) * wa;
86 a_re = zp[0] + 2.0;
87 c_re = zp[0] - 2.0;
88 a_im =
89 c_im = zp[1];
90 zp[0] = (a_re * c_re + a_im * c_im) / (c_re * c_re + c_im * c_im);
91 zp[1] = (a_im * c_re - a_re * c_im) / (c_re * c_re + c_im * c_im);
92
93 for(j = order; j >= 1; j--)
94 {
95 a_re = p[j][0];
96 a_im = p[j][1];
97 p[j][0] = a_re*zp[0] - a_im*zp[1] + p[j-1][0];
98 p[j][1] = a_re*zp[1] + a_im*zp[0] + p[j-1][1];
99 }
100 a_re = p[0][0]*zp[0] - p[0][1]*zp[1];
101 p[0][1] = p[0][0]*zp[1] + p[0][1]*zp[0];
102 p[0][0] = a_re;
103 }
104 c->gain = p[order][0];
105 for(i = 0; i < order; i++){
106 c->gain += p[i][0];
107 c->cy[i] = (-p[i][0] * p[order][0] + -p[i][1] * p[order][1]) /
108 (p[order][0] * p[order][0] + p[order][1] * p[order][1]);
109 }
110 c->gain /= 1 << order;
111
112 return 0;
113 }
114
115 av_cold struct FFIIRFilterCoeffs* ff_iir_filter_init_coeffs(void *avc,
116 enum IIRFilterType filt_type,
117 enum IIRFilterMode filt_mode,
118 int order, float cutoff_ratio,
119 float stopband, float ripple)
120 {
121 FFIIRFilterCoeffs *c;
122
123 if (order <= 0 || order > MAXORDER || cutoff_ratio >= 1.0)
124 return NULL;
125
126 FF_ALLOCZ_OR_GOTO(avc, c, sizeof(FFIIRFilterCoeffs),
127 init_fail);
128 FF_ALLOC_OR_GOTO (avc, c->cx, sizeof(c->cx[0]) * ((order >> 1) + 1),
129 init_fail);
130 FF_ALLOC_OR_GOTO (avc, c->cy, sizeof(c->cy[0]) * order,
131 init_fail);
132 c->order = order;
133
134 if (filt_type == FF_FILTER_TYPE_BUTTERWORTH) {
135 if (butterworth_init_coeffs(avc, c, filt_mode, order, cutoff_ratio,
136 stopband)) {
137 goto init_fail;
138 }
139 } else {
140 av_log(avc, AV_LOG_ERROR, "filter type is not currently implemented\n");
141 goto init_fail;
142 }
143
144 return c;
145
146 init_fail:
147 ff_iir_filter_free_coeffs(c);
148 return NULL;
149 }
150
151 av_cold struct FFIIRFilterState* ff_iir_filter_init_state(int order)
152 {
153 FFIIRFilterState* s = av_mallocz(sizeof(FFIIRFilterState) + sizeof(s->x[0]) * (order - 1));
154 return s;
155 }
156
157 #define CONV_S16(dest, source) dest = av_clip_int16(lrintf(source));
158
159 #define CONV_FLT(dest, source) dest = source;
160
161 #define FILTER_BW_O4_1(i0, i1, i2, i3, fmt) \
162 in = *src0 * c->gain \
163 + c->cy[0]*s->x[i0] + c->cy[1]*s->x[i1] \
164 + c->cy[2]*s->x[i2] + c->cy[3]*s->x[i3]; \
165 res = (s->x[i0] + in )*1 \
166 + (s->x[i1] + s->x[i3])*4 \
167 + s->x[i2] *6; \
168 CONV_##fmt(*dst0, res) \
169 s->x[i0] = in; \
170 src0 += sstep; \
171 dst0 += dstep;
172
173 #define FILTER_BW_O4(type, fmt) { \
174 int i; \
175 const type *src0 = src; \
176 type *dst0 = dst; \
177 for (i = 0; i < size; i += 4) { \
178 float in, res; \
179 FILTER_BW_O4_1(0, 1, 2, 3, fmt); \
180 FILTER_BW_O4_1(1, 2, 3, 0, fmt); \
181 FILTER_BW_O4_1(2, 3, 0, 1, fmt); \
182 FILTER_BW_O4_1(3, 0, 1, 2, fmt); \
183 } \
184 }
185
186 #define FILTER_DIRECT_FORM_II(type, fmt) { \
187 int i; \
188 const type *src0 = src; \
189 type *dst0 = dst; \
190 for (i = 0; i < size; i++) { \
191 int j; \
192 float in, res; \
193 in = *src0 * c->gain; \
194 for(j = 0; j < c->order; j++) \
195 in += c->cy[j] * s->x[j]; \
196 res = s->x[0] + in + s->x[c->order >> 1] * c->cx[c->order >> 1]; \
197 for(j = 1; j < c->order >> 1; j++) \
198 res += (s->x[j] + s->x[c->order - j]) * c->cx[j]; \
199 for(j = 0; j < c->order - 1; j++) \
200 s->x[j] = s->x[j + 1]; \
201 CONV_##fmt(*dst0, res) \
202 s->x[c->order - 1] = in; \
203 src0 += sstep; \
204 dst0 += dstep; \
205 } \
206 }
207
208 void ff_iir_filter(const struct FFIIRFilterCoeffs *c,
209 struct FFIIRFilterState *s, int size,
210 const int16_t *src, int sstep, int16_t *dst, int dstep)
211 {
212 if (c->order == 4) {
213 FILTER_BW_O4(int16_t, S16)
214 } else {
215 FILTER_DIRECT_FORM_II(int16_t, S16)
216 }
217 }
218
219 void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *c,
220 struct FFIIRFilterState *s, int size,
221 const float *src, int sstep, void *dst, int dstep)
222 {
223 if (c->order == 4) {
224 FILTER_BW_O4(float, FLT)
225 } else {
226 FILTER_DIRECT_FORM_II(float, FLT)
227 }
228 }
229
230 av_cold void ff_iir_filter_free_state(struct FFIIRFilterState *state)
231 {
232 av_free(state);
233 }
234
235 av_cold void ff_iir_filter_free_coeffs(struct FFIIRFilterCoeffs *coeffs)
236 {
237 if(coeffs){
238 av_free(coeffs->cx);
239 av_free(coeffs->cy);
240 }
241 av_free(coeffs);
242 }
243
244 #ifdef TEST
245 #define FILT_ORDER 4
246 #define SIZE 1024
247 int main(void)
248 {
249 struct FFIIRFilterCoeffs *fcoeffs = NULL;
250 struct FFIIRFilterState *fstate = NULL;
251 float cutoff_coeff = 0.4;
252 int16_t x[SIZE], y[SIZE];
253 int i;
254 FILE* fd;
255
256 fcoeffs = ff_iir_filter_init_coeffs(FF_FILTER_TYPE_BUTTERWORTH,
257 FF_FILTER_MODE_LOWPASS, FILT_ORDER,
258 cutoff_coeff, 0.0, 0.0);
259 fstate = ff_iir_filter_init_state(FILT_ORDER);
260
261 for (i = 0; i < SIZE; i++) {
262 x[i] = lrint(0.75 * INT16_MAX * sin(0.5*M_PI*i*i/SIZE));
263 }
264
265 ff_iir_filter(fcoeffs, fstate, SIZE, x, 1, y, 1);
266
267 fd = fopen("in.bin", "w");
268 fwrite(x, sizeof(x[0]), SIZE, fd);
269 fclose(fd);
270
271 fd = fopen("out.bin", "w");
272 fwrite(y, sizeof(y[0]), SIZE, fd);
273 fclose(fd);
274
275 ff_iir_filter_free_coeffs(fcoeffs);
276 ff_iir_filter_free_state(fstate);
277 return 0;
278 }
279 #endif /* TEST */