testprogs: K&R formatting cosmetics
[ffmpeg.git] / libavcodec / iirfilter.c
1 /*
2  * IIR filter
3  * Copyright (c) 2008 Konstantin Shishkov
4  *
5  * This file is part of Libav.
6  *
7  * Libav 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  * Libav 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 Libav; 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 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     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
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 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     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
199 init_fail:
200     ff_iir_filter_free_coeffs(c);
201     return NULL;
202 }
203
204 av_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
279 void ff_iir_filter(const struct FFIIRFilterCoeffs *c,
280                    struct FFIIRFilterState *s, int size,
281                    const int16_t *src, int sstep, int16_t *dst, int dstep)
282 {
283     if (c->order == 2) {
284         FILTER_O2(int16_t, S16)
285     } else if (c->order == 4) {
286         FILTER_BW_O4(int16_t, S16)
287     } else {
288         FILTER_DIRECT_FORM_II(int16_t, S16)
289     }
290 }
291
292 void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *c,
293                        struct FFIIRFilterState *s, int size,
294                        const float *src, int sstep, float *dst, int dstep)
295 {
296     if (c->order == 2) {
297         FILTER_O2(float, FLT)
298     } else if (c->order == 4) {
299         FILTER_BW_O4(float, FLT)
300     } else {
301         FILTER_DIRECT_FORM_II(float, FLT)
302     }
303 }
304
305 av_cold void ff_iir_filter_free_state(struct FFIIRFilterState *state)
306 {
307     av_free(state);
308 }
309
310 av_cold void ff_iir_filter_free_coeffs(struct FFIIRFilterCoeffs *coeffs)
311 {
312     if (coeffs) {
313         av_free(coeffs->cx);
314         av_free(coeffs->cy);
315     }
316     av_free(coeffs);
317 }
318
319 #ifdef TEST
320 #include <stdio.h>
321
322 #define FILT_ORDER 4
323 #define SIZE 1024
324 int main(void)
325 {
326     struct FFIIRFilterCoeffs *fcoeffs = NULL;
327     struct FFIIRFilterState  *fstate  = NULL;
328     float cutoff_coeff = 0.4;
329     int16_t x[SIZE], y[SIZE];
330     int i;
331
332     fcoeffs = ff_iir_filter_init_coeffs(NULL, FF_FILTER_TYPE_BUTTERWORTH,
333                                         FF_FILTER_MODE_LOWPASS, FILT_ORDER,
334                                         cutoff_coeff, 0.0, 0.0);
335     fstate  = ff_iir_filter_init_state(FILT_ORDER);
336
337     for (i = 0; i < SIZE; i++)
338         x[i] = lrint(0.75 * INT16_MAX * sin(0.5 * M_PI * i * i / SIZE));
339
340     ff_iir_filter(fcoeffs, fstate, SIZE, x, 1, y, 1);
341
342     for (i = 0; i < SIZE; i++)
343         printf("%6d %6d\n", x[i], y[i]);
344
345     ff_iir_filter_free_coeffs(fcoeffs);
346     ff_iir_filter_free_state(fstate);
347     return 0;
348 }
349 #endif /* TEST */