rv34: export qp table
[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/common.h"
30
31 /**
32  * IIR filter global parameters
33  */
34 typedef struct FFIIRFilterCoeffs{
35     int   order;
36     float gain;
37     int   *cx;
38     float *cy;
39 }FFIIRFilterCoeffs;
40
41 /**
42  * IIR filter state
43  */
44 typedef struct FFIIRFilterState{
45     float x[1];
46 }FFIIRFilterState;
47
48 /// maximum supported filter order
49 #define MAXORDER 30
50
51 static int butterworth_init_coeffs(void *avc, struct FFIIRFilterCoeffs *c,
52                                    enum IIRFilterMode filt_mode,
53                                    int order, float cutoff_ratio,
54                                    float stopband)
55 {
56     int i, j;
57     double wa;
58     double p[MAXORDER + 1][2];
59
60     if (filt_mode != FF_FILTER_MODE_LOWPASS) {
61         av_log(avc, AV_LOG_ERROR, "Butterworth filter currently only supports "
62                "low-pass filter mode\n");
63         return -1;
64     }
65     if (order & 1) {
66         av_log(avc, AV_LOG_ERROR, "Butterworth filter currently only supports "
67                "even filter orders\n");
68         return -1;
69     }
70
71     wa = 2 * tan(M_PI * 0.5 * cutoff_ratio);
72
73     c->cx[0] = 1;
74     for(i = 1; i < (order >> 1) + 1; i++)
75         c->cx[i] = c->cx[i - 1] * (order - i + 1LL) / i;
76
77     p[0][0] = 1.0;
78     p[0][1] = 0.0;
79     for(i = 1; i <= order; i++)
80         p[i][0] = p[i][1] = 0.0;
81     for(i = 0; i < order; i++){
82         double zp[2];
83         double th = (i + (order >> 1) + 0.5) * M_PI / order;
84         double a_re, a_im, c_re, c_im;
85         zp[0] = cos(th) * wa;
86         zp[1] = sin(th) * wa;
87         a_re = zp[0] + 2.0;
88         c_re = zp[0] - 2.0;
89         a_im =
90         c_im = zp[1];
91         zp[0] = (a_re * c_re + a_im * c_im) / (c_re * c_re + c_im * c_im);
92         zp[1] = (a_im * c_re - a_re * c_im) / (c_re * c_re + c_im * c_im);
93
94         for(j = order; j >= 1; j--)
95         {
96             a_re = p[j][0];
97             a_im = p[j][1];
98             p[j][0] = a_re*zp[0] - a_im*zp[1] + p[j-1][0];
99             p[j][1] = a_re*zp[1] + a_im*zp[0] + p[j-1][1];
100         }
101         a_re    = p[0][0]*zp[0] - p[0][1]*zp[1];
102         p[0][1] = p[0][0]*zp[1] + p[0][1]*zp[0];
103         p[0][0] = a_re;
104     }
105     c->gain = p[order][0];
106     for(i = 0; i < order; i++){
107         c->gain += p[i][0];
108         c->cy[i] = (-p[i][0] * p[order][0] + -p[i][1] * p[order][1]) /
109                    (p[order][0] * p[order][0] + p[order][1] * p[order][1]);
110     }
111     c->gain /= 1 << order;
112
113     return 0;
114 }
115
116 static int biquad_init_coeffs(void *avc, struct FFIIRFilterCoeffs *c,
117                               enum IIRFilterMode filt_mode, int order,
118                               float cutoff_ratio, float stopband)
119 {
120     double cos_w0, sin_w0;
121     double a0, x0, x1;
122
123     if (filt_mode != FF_FILTER_MODE_HIGHPASS &&
124         filt_mode != FF_FILTER_MODE_LOWPASS) {
125         av_log(avc, AV_LOG_ERROR, "Biquad filter currently only supports "
126                "high-pass and low-pass filter modes\n");
127         return -1;
128     }
129     if (order != 2) {
130         av_log(avc, AV_LOG_ERROR, "Biquad filter must have order of 2\n");
131         return -1;
132     }
133
134     cos_w0 = cos(M_PI * cutoff_ratio);
135     sin_w0 = sin(M_PI * cutoff_ratio);
136
137     a0 = 1.0 + (sin_w0 / 2.0);
138
139     if (filt_mode == FF_FILTER_MODE_HIGHPASS) {
140         c->gain  =  ((1.0 + cos_w0) / 2.0)  / a0;
141         x0       =  ((1.0 + cos_w0) / 2.0)  / a0;
142         x1       = (-(1.0 + cos_w0))        / a0;
143     } else { // FF_FILTER_MODE_LOWPASS
144         c->gain  =  ((1.0 - cos_w0) / 2.0)  / a0;
145         x0       =  ((1.0 - cos_w0) / 2.0)  / a0;
146         x1       =   (1.0 - cos_w0)         / a0;
147     }
148     c->cy[0] = (-1.0 + (sin_w0 / 2.0)) / a0;
149     c->cy[1] =  (2.0 *  cos_w0)        / a0;
150
151     // divide by gain to make the x coeffs integers.
152     // during filtering, the delay state will include the gain multiplication
153     c->cx[0] = lrintf(x0 / c->gain);
154     c->cx[1] = lrintf(x1 / c->gain);
155
156     return 0;
157 }
158
159 av_cold struct FFIIRFilterCoeffs* ff_iir_filter_init_coeffs(void *avc,
160                                                 enum IIRFilterType filt_type,
161                                                 enum IIRFilterMode filt_mode,
162                                                 int order, float cutoff_ratio,
163                                                 float stopband, float ripple)
164 {
165     FFIIRFilterCoeffs *c;
166     int ret = 0;
167
168     if (order <= 0 || order > MAXORDER || cutoff_ratio >= 1.0)
169         return NULL;
170
171     FF_ALLOCZ_OR_GOTO(avc, c,     sizeof(FFIIRFilterCoeffs),
172                       init_fail);
173     FF_ALLOC_OR_GOTO (avc, c->cx, sizeof(c->cx[0]) * ((order >> 1) + 1),
174                       init_fail);
175     FF_ALLOC_OR_GOTO (avc, c->cy, sizeof(c->cy[0]) * order,
176                       init_fail);
177     c->order = order;
178
179     switch (filt_type) {
180     case FF_FILTER_TYPE_BUTTERWORTH:
181         ret = butterworth_init_coeffs(avc, c, filt_mode, order, cutoff_ratio,
182                                       stopband);
183         break;
184     case FF_FILTER_TYPE_BIQUAD:
185         ret = biquad_init_coeffs(avc, c, filt_mode, order, cutoff_ratio,
186                                  stopband);
187         break;
188     default:
189         av_log(avc, AV_LOG_ERROR, "filter type is not currently implemented\n");
190         goto init_fail;
191     }
192
193     if (!ret)
194         return c;
195
196 init_fail:
197     ff_iir_filter_free_coeffs(c);
198     return NULL;
199 }
200
201 av_cold struct FFIIRFilterState* ff_iir_filter_init_state(int order)
202 {
203     FFIIRFilterState* s = av_mallocz(sizeof(FFIIRFilterState) + sizeof(s->x[0]) * (order - 1));
204     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] + c->cy[1]*s->x[i1]    \
214          + c->cy[2]*s->x[i2] + c->cy[3]*s->x[i3];   \
215     res =  (s->x[i0] + in      )*1                  \
216          + (s->x[i1] + s->x[i3])*4                  \
217          +  s->x[i2]            *6;                 \
218     CONV_##fmt(*dst0, res)                          \
219     s->x[i0] = in;                                  \
220     src0 += sstep;                                  \
221     dst0 += dstep;
222
223 #define FILTER_BW_O4(type, fmt) {           \
224     int i;                                  \
225     const type *src0 = src;                 \
226     type       *dst0 = dst;                 \
227     for (i = 0; i < size; i += 4) {         \
228         float in, res;                      \
229         FILTER_BW_O4_1(0, 1, 2, 3, fmt);    \
230         FILTER_BW_O4_1(1, 2, 3, 0, fmt);    \
231         FILTER_BW_O4_1(2, 3, 0, 1, fmt);    \
232         FILTER_BW_O4_1(3, 0, 1, 2, fmt);    \
233     }                                       \
234 }
235
236 #define FILTER_DIRECT_FORM_II(type, fmt) {                                  \
237     int i;                                                                  \
238     const type *src0 = src;                                                 \
239     type       *dst0 = dst;                                                 \
240     for (i = 0; i < size; i++) {                                            \
241         int j;                                                              \
242         float in, res;                                                      \
243         in = *src0 * c->gain;                                               \
244         for(j = 0; j < c->order; j++)                                       \
245             in += c->cy[j] * s->x[j];                                       \
246         res = s->x[0] + in + s->x[c->order >> 1] * c->cx[c->order >> 1];    \
247         for(j = 1; j < c->order >> 1; j++)                                  \
248             res += (s->x[j] + s->x[c->order - j]) * c->cx[j];               \
249         for(j = 0; j < c->order - 1; j++)                                   \
250             s->x[j] = s->x[j + 1];                                          \
251         CONV_##fmt(*dst0, res)                                              \
252         s->x[c->order - 1] = in;                                            \
253         src0 += sstep;                                                      \
254         dst0 += dstep;                                                      \
255     }                                                                       \
256 }
257
258 #define FILTER_O2(type, fmt) {                                              \
259     int i;                                                                  \
260     const type *src0 = src;                                                 \
261     type       *dst0 = dst;                                                 \
262     for (i = 0; i < size; i++) {                                            \
263         float in = *src0   * c->gain  +                                     \
264                    s->x[0] * c->cy[0] +                                     \
265                    s->x[1] * c->cy[1];                                      \
266         CONV_##fmt(*dst0, s->x[0] + in + s->x[1] * c->cx[1])                \
267         s->x[0] = s->x[1];                                                  \
268         s->x[1] = in;                                                       \
269         src0 += sstep;                                                      \
270         dst0 += dstep;                                                      \
271     }                                                                       \
272 }
273
274 void ff_iir_filter(const struct FFIIRFilterCoeffs *c,
275                    struct FFIIRFilterState *s, int size,
276                    const int16_t *src, int sstep, int16_t *dst, int dstep)
277 {
278     if (c->order == 2) {
279         FILTER_O2(int16_t, S16)
280     } else if (c->order == 4) {
281         FILTER_BW_O4(int16_t, S16)
282     } else {
283         FILTER_DIRECT_FORM_II(int16_t, S16)
284     }
285 }
286
287 void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *c,
288                        struct FFIIRFilterState *s, int size,
289                        const float *src, int sstep, float *dst, int dstep)
290 {
291     if (c->order == 2) {
292         FILTER_O2(float, FLT)
293     } else if (c->order == 4) {
294         FILTER_BW_O4(float, FLT)
295     } else {
296         FILTER_DIRECT_FORM_II(float, FLT)
297     }
298 }
299
300 av_cold void ff_iir_filter_free_state(struct FFIIRFilterState *state)
301 {
302     av_free(state);
303 }
304
305 av_cold void ff_iir_filter_free_coeffs(struct FFIIRFilterCoeffs *coeffs)
306 {
307     if(coeffs){
308         av_free(coeffs->cx);
309         av_free(coeffs->cy);
310     }
311     av_free(coeffs);
312 }
313
314 #ifdef TEST
315 #include <stdio.h>
316
317 #define FILT_ORDER 4
318 #define SIZE 1024
319 int main(void)
320 {
321     struct FFIIRFilterCoeffs *fcoeffs = NULL;
322     struct FFIIRFilterState  *fstate  = NULL;
323     float cutoff_coeff = 0.4;
324     int16_t x[SIZE], y[SIZE];
325     int i;
326
327     fcoeffs = ff_iir_filter_init_coeffs(NULL, FF_FILTER_TYPE_BUTTERWORTH,
328                                         FF_FILTER_MODE_LOWPASS, FILT_ORDER,
329                                         cutoff_coeff, 0.0, 0.0);
330     fstate  = ff_iir_filter_init_state(FILT_ORDER);
331
332     for (i = 0; i < SIZE; i++) {
333         x[i] = lrint(0.75 * INT16_MAX * sin(0.5*M_PI*i*i/SIZE));
334     }
335
336     ff_iir_filter(fcoeffs, fstate, SIZE, x, 1, y, 1);
337
338     for (i = 0; i < SIZE; i++)
339         printf("%6d %6d\n", x[i], y[i]);
340
341     ff_iir_filter_free_coeffs(fcoeffs);
342     ff_iir_filter_free_state(fstate);
343     return 0;
344 }
345 #endif /* TEST */