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iirfilter.c
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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;
43 
44 /**
45  * IIR filter state
46  */
47 typedef struct FFIIRFilterState {
48  float x[1];
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 
163  enum IIRFilterType filt_type,
164  enum IIRFilterMode filt_mode,
165  int order, float cutoff_ratio,
166  float stopband, float ripple)
167 {
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) {
184  ret = butterworth_init_coeffs(avc, c, filt_mode, order, cutoff_ratio,
185  stopband);
186  break;
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:
201  return NULL;
202 }
203 
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 
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 
306 {
307  av_freep(state);
308 }
309 
311 {
312  struct FFIIRFilterCoeffs *coeffs = *coeffsp;
313  if (coeffs) {
314  av_freep(&coeffs->cx);
315  av_freep(&coeffs->cy);
316  }
317  av_freep(coeffsp);
318 }
319 
322 
323  if (HAVE_MIPSFPU)
325 }
#define NULL
Definition: coverity.c:32
static av_cold int biquad_init_coeffs(void *avc, struct FFIIRFilterCoeffs *c, enum IIRFilterMode filt_mode, int order, float cutoff_ratio, float stopband)
Definition: iirfilter.c:119
const char * s
Definition: avisynth_c.h:768
void(* filter_flt)(const struct FFIIRFilterCoeffs *coeffs, struct FFIIRFilterState *state, int size, const float *src, int sstep, float *dst, int dstep)
Perform IIR filtering on floating-point input samples.
Definition: iirfilter.h:62
#define a0
Definition: regdef.h:46
IIRFilterMode
Definition: iirfilter.h:43
void * av_mallocz(size_t size)
Allocate a memory block with alignment suitable for all memory accesses (including vectors if availab...
Definition: mem.c:252
#define src
Definition: vp8dsp.c:254
av_cold struct FFIIRFilterState * ff_iir_filter_init_state(int order)
Create new filter state.
Definition: iirfilter.c:204
Macro definitions for various function/variable attributes.
av_cold struct FFIIRFilterCoeffs * ff_iir_filter_init_coeffs(void *avc, enum IIRFilterType filt_type, enum IIRFilterMode filt_mode, int order, float cutoff_ratio, float stopband, float ripple)
Initialize filter coefficients.
Definition: iirfilter.c:162
#define av_cold
Definition: attributes.h:82
#define lrintf(x)
Definition: libm_mips.h:70
ptrdiff_t size
Definition: opengl_enc.c:101
#define av_log(a,...)
#define FILTER_DIRECT_FORM_II(type, fmt)
Definition: iirfilter.c:241
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:176
av_cold void ff_iir_filter_free_statep(struct FFIIRFilterState **state)
Free and zero filter state.
Definition: iirfilter.c:305
IIR filter state.
Definition: iirfilter.c:47
void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *c, struct FFIIRFilterState *s, int size, const float *src, int sstep, float *dst, int dstep)
Perform IIR filtering on floating-point input samples.
Definition: iirfilter.c:292
#define th
Definition: regdef.h:75
#define FILTER_O2(type, fmt)
Definition: iirfilter.c:263
#define MAXORDER
maximum supported filter order
Definition: iirfilter.c:52
#define FILTER_BW_O4(type, fmt)
Definition: iirfilter.c:228
static av_cold int butterworth_init_coeffs(void *avc, struct FFIIRFilterCoeffs *c, enum IIRFilterMode filt_mode, int order, float cutoff_ratio, float stopband)
Definition: iirfilter.c:54
float x[1]
Definition: iirfilter.c:48
void ff_iir_filter(const struct FFIIRFilterCoeffs *c, struct FFIIRFilterState *s, int size, const int16_t *src, int sstep, int16_t *dst, int dstep)
Perform IIR filtering on signed 16-bit input samples.
Definition: iirfilter.c:279
static struct @246 state
IIRFilterType
Definition: iirfilter.h:35
IIR filter global parameters.
Definition: iirfilter.c:37
void ff_iir_filter_init_mips(FFIIRFilterContext *f)
void ff_iir_filter_init(FFIIRFilterContext *f)
Initialize FFIIRFilterContext.
Definition: iirfilter.c:320
common internal and external API header
#define FF_ALLOC_OR_GOTO(ctx, p, size, label)
Definition: internal.h:130
IIR filter interface.
static const int16_t coeffs[]
static AVCodec * c
#define av_freep(p)
#define M_PI
Definition: mathematics.h:52
av_cold void ff_iir_filter_free_coeffsp(struct FFIIRFilterCoeffs **coeffsp)
Free filter coefficients.
Definition: iirfilter.c:310
#define FF_ALLOCZ_OR_GOTO(ctx, p, size, label)
Definition: internal.h:139