Merge commit '3c650efb81aaa3b395ba4606ee68a47ee4efb57b'
[ffmpeg.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 #include "libavutil/attributes.h"
30 #include "libavutil/common.h"
31
32 /**
33  * IIR filter global parameters
34  */
35 typedef struct FFIIRFilterCoeffs{
36     int   order;
37     float gain;
38     int   *cx;
39     float *cy;
40 }FFIIRFilterCoeffs;
41
42 /**
43  * IIR filter state
44  */
45 typedef struct FFIIRFilterState{
46     float x[1];
47 }FFIIRFilterState;
48
49 /// maximum supported filter order
50 #define MAXORDER 30
51
52 static av_cold int butterworth_init_coeffs(void *avc,
53                                            struct FFIIRFilterCoeffs *c,
54                                            enum IIRFilterMode filt_mode,
55                                            int order, float cutoff_ratio,
56                                            float stopband)
57 {
58     int i, j;
59     double wa;
60     double p[MAXORDER + 1][2];
61
62     if (filt_mode != FF_FILTER_MODE_LOWPASS) {
63         av_log(avc, AV_LOG_ERROR, "Butterworth filter currently only supports "
64                "low-pass filter mode\n");
65         return -1;
66     }
67     if (order & 1) {
68         av_log(avc, AV_LOG_ERROR, "Butterworth filter currently only supports "
69                "even filter orders\n");
70         return -1;
71     }
72
73     wa = 2 * tan(M_PI * 0.5 * cutoff_ratio);
74
75     c->cx[0] = 1;
76     for(i = 1; i < (order >> 1) + 1; i++)
77         c->cx[i] = c->cx[i - 1] * (order - i + 1LL) / i;
78
79     p[0][0] = 1.0;
80     p[0][1] = 0.0;
81     for(i = 1; i <= order; i++)
82         p[i][0] = p[i][1] = 0.0;
83     for(i = 0; i < order; i++){
84         double zp[2];
85         double th = (i + (order >> 1) + 0.5) * M_PI / order;
86         double a_re, a_im, c_re, c_im;
87         zp[0] = cos(th) * wa;
88         zp[1] = sin(th) * wa;
89         a_re = zp[0] + 2.0;
90         c_re = zp[0] - 2.0;
91         a_im =
92         c_im = zp[1];
93         zp[0] = (a_re * c_re + a_im * c_im) / (c_re * c_re + c_im * c_im);
94         zp[1] = (a_im * c_re - a_re * c_im) / (c_re * c_re + c_im * c_im);
95
96         for(j = order; j >= 1; j--)
97         {
98             a_re = p[j][0];
99             a_im = p[j][1];
100             p[j][0] = a_re*zp[0] - a_im*zp[1] + p[j-1][0];
101             p[j][1] = a_re*zp[1] + a_im*zp[0] + p[j-1][1];
102         }
103         a_re    = p[0][0]*zp[0] - p[0][1]*zp[1];
104         p[0][1] = p[0][0]*zp[1] + p[0][1]*zp[0];
105         p[0][0] = a_re;
106     }
107     c->gain = p[order][0];
108     for(i = 0; i < order; i++){
109         c->gain += p[i][0];
110         c->cy[i] = (-p[i][0] * p[order][0] + -p[i][1] * p[order][1]) /
111                    (p[order][0] * p[order][0] + p[order][1] * p[order][1]);
112     }
113     c->gain /= 1 << order;
114
115     return 0;
116 }
117
118 static av_cold int biquad_init_coeffs(void *avc, struct FFIIRFilterCoeffs *c,
119                                       enum IIRFilterMode filt_mode, int order,
120                                       float cutoff_ratio, float stopband)
121 {
122     double cos_w0, sin_w0;
123     double a0, x0, x1;
124
125     if (filt_mode != FF_FILTER_MODE_HIGHPASS &&
126         filt_mode != FF_FILTER_MODE_LOWPASS) {
127         av_log(avc, AV_LOG_ERROR, "Biquad filter currently only supports "
128                "high-pass and low-pass filter modes\n");
129         return -1;
130     }
131     if (order != 2) {
132         av_log(avc, AV_LOG_ERROR, "Biquad filter must have order of 2\n");
133         return -1;
134     }
135
136     cos_w0 = cos(M_PI * cutoff_ratio);
137     sin_w0 = sin(M_PI * cutoff_ratio);
138
139     a0 = 1.0 + (sin_w0 / 2.0);
140
141     if (filt_mode == FF_FILTER_MODE_HIGHPASS) {
142         c->gain  =  ((1.0 + cos_w0) / 2.0)  / a0;
143         x0       =  ((1.0 + cos_w0) / 2.0)  / a0;
144         x1       = (-(1.0 + cos_w0))        / a0;
145     } else { // FF_FILTER_MODE_LOWPASS
146         c->gain  =  ((1.0 - cos_w0) / 2.0)  / a0;
147         x0       =  ((1.0 - cos_w0) / 2.0)  / a0;
148         x1       =   (1.0 - cos_w0)         / a0;
149     }
150     c->cy[0] = (-1.0 + (sin_w0 / 2.0)) / a0;
151     c->cy[1] =  (2.0 *  cos_w0)        / a0;
152
153     // divide by gain to make the x coeffs integers.
154     // during filtering, the delay state will include the gain multiplication
155     c->cx[0] = lrintf(x0 / c->gain);
156     c->cx[1] = lrintf(x1 / c->gain);
157
158     return 0;
159 }
160
161 av_cold struct FFIIRFilterCoeffs* ff_iir_filter_init_coeffs(void *avc,
162                                                 enum IIRFilterType filt_type,
163                                                 enum IIRFilterMode filt_mode,
164                                                 int order, float cutoff_ratio,
165                                                 float stopband, float ripple)
166 {
167     FFIIRFilterCoeffs *c;
168     int ret = 0;
169
170     if (order <= 0 || order > MAXORDER || cutoff_ratio >= 1.0)
171         return NULL;
172
173     FF_ALLOCZ_OR_GOTO(avc, c,     sizeof(FFIIRFilterCoeffs),
174                       init_fail);
175     FF_ALLOC_OR_GOTO (avc, c->cx, sizeof(c->cx[0]) * ((order >> 1) + 1),
176                       init_fail);
177     FF_ALLOC_OR_GOTO (avc, c->cy, sizeof(c->cy[0]) * order,
178                       init_fail);
179     c->order = order;
180
181     switch (filt_type) {
182     case FF_FILTER_TYPE_BUTTERWORTH:
183         ret = butterworth_init_coeffs(avc, c, filt_mode, order, cutoff_ratio,
184                                       stopband);
185         break;
186     case FF_FILTER_TYPE_BIQUAD:
187         ret = biquad_init_coeffs(avc, c, filt_mode, order, cutoff_ratio,
188                                  stopband);
189         break;
190     default:
191         av_log(avc, AV_LOG_ERROR, "filter type is not currently implemented\n");
192         goto init_fail;
193     }
194
195     if (!ret)
196         return c;
197
198 init_fail:
199     ff_iir_filter_free_coeffs(c);
200     return NULL;
201 }
202
203 av_cold struct FFIIRFilterState* ff_iir_filter_init_state(int order)
204 {
205     FFIIRFilterState* s = av_mallocz(sizeof(FFIIRFilterState) + sizeof(s->x[0]) * (order - 1));
206     return s;
207 }
208
209 #define CONV_S16(dest, source) dest = av_clip_int16(lrintf(source));
210
211 #define CONV_FLT(dest, source) dest = source;
212
213 #define FILTER_BW_O4_1(i0, i1, i2, i3, fmt)         \
214     in = *src0 * c->gain                            \
215          + c->cy[0]*s->x[i0] + c->cy[1]*s->x[i1]    \
216          + c->cy[2]*s->x[i2] + 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 void ff_iir_filter(const struct FFIIRFilterCoeffs *c,
277                    struct FFIIRFilterState *s, int size,
278                    const int16_t *src, int sstep, int16_t *dst, int dstep)
279 {
280     if (c->order == 2) {
281         FILTER_O2(int16_t, S16)
282     } else if (c->order == 4) {
283         FILTER_BW_O4(int16_t, S16)
284     } else {
285         FILTER_DIRECT_FORM_II(int16_t, S16)
286     }
287 }
288
289 void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *c,
290                        struct FFIIRFilterState *s, int size,
291                        const float *src, int sstep, float *dst, int dstep)
292 {
293     if (c->order == 2) {
294         FILTER_O2(float, FLT)
295     } else if (c->order == 4) {
296         FILTER_BW_O4(float, FLT)
297     } else {
298         FILTER_DIRECT_FORM_II(float, FLT)
299     }
300 }
301
302 av_cold void ff_iir_filter_free_state(struct FFIIRFilterState *state)
303 {
304     av_free(state);
305 }
306
307 av_cold void ff_iir_filter_free_coeffs(struct FFIIRFilterCoeffs *coeffs)
308 {
309     if(coeffs){
310         av_free(coeffs->cx);
311         av_free(coeffs->cy);
312     }
313     av_free(coeffs);
314 }
315
316 void ff_iir_filter_init(FFIIRFilterContext *f) {
317     f->filter_flt = ff_iir_filter_flt;
318
319     if (HAVE_MIPSFPU)
320         ff_iir_filter_init_mips(f);
321 }
322
323 #ifdef TEST
324 #include <stdio.h>
325
326 #define FILT_ORDER 4
327 #define SIZE 1024
328 int main(void)
329 {
330     struct FFIIRFilterCoeffs *fcoeffs = NULL;
331     struct FFIIRFilterState  *fstate  = NULL;
332     float cutoff_coeff = 0.4;
333     int16_t x[SIZE], y[SIZE];
334     int i;
335
336     fcoeffs = ff_iir_filter_init_coeffs(NULL, FF_FILTER_TYPE_BUTTERWORTH,
337                                         FF_FILTER_MODE_LOWPASS, FILT_ORDER,
338                                         cutoff_coeff, 0.0, 0.0);
339     fstate  = ff_iir_filter_init_state(FILT_ORDER);
340
341     for (i = 0; i < SIZE; i++) {
342         x[i] = lrint(0.75 * INT16_MAX * sin(0.5*M_PI*i*i/SIZE));
343     }
344
345     ff_iir_filter(fcoeffs, fstate, SIZE, x, 1, y, 1);
346
347     for (i = 0; i < SIZE; i++)
348         printf("%6d %6d\n", x[i], y[i]);
349
350     ff_iir_filter_free_coeffs(fcoeffs);
351     ff_iir_filter_free_state(fstate);
352     return 0;
353 }
354 #endif /* TEST */