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asrc_sine.c
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1 /*
2  * Copyright (c) 2013 Nicolas George
3  *
4  * This file is part of FFmpeg.
5  *
6  * FFmpeg is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public License
8  * as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * FFmpeg is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14  * GNU Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public License
17  * along with FFmpeg; if not, write to the Free Software Foundation, Inc.,
18  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 #include <float.h>
22 
23 #include "libavutil/avassert.h"
25 #include "libavutil/opt.h"
26 #include "audio.h"
27 #include "avfilter.h"
28 #include "internal.h"
29 
30 typedef struct {
31  const AVClass *class;
32  double frequency;
33  double beep_factor;
36  int64_t duration;
37  int16_t *sin;
38  int64_t pts;
39  uint32_t phi; ///< current phase of the sine (2pi = 1<<32)
40  uint32_t dphi; ///< phase increment between two samples
41  unsigned beep_period;
42  unsigned beep_index;
43  unsigned beep_length;
44  uint32_t phi_beep; ///< current phase of the beep
45  uint32_t dphi_beep; ///< phase increment of the beep
46 } SineContext;
47 
48 #define CONTEXT SineContext
49 #define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
50 
51 #define OPT_GENERIC(name, field, def, min, max, descr, type, deffield, ...) \
52  { name, descr, offsetof(CONTEXT, field), AV_OPT_TYPE_ ## type, \
53  { .deffield = def }, min, max, FLAGS, __VA_ARGS__ }
54 
55 #define OPT_INT(name, field, def, min, max, descr, ...) \
56  OPT_GENERIC(name, field, def, min, max, descr, INT, i64, __VA_ARGS__)
57 
58 #define OPT_DBL(name, field, def, min, max, descr, ...) \
59  OPT_GENERIC(name, field, def, min, max, descr, DOUBLE, dbl, __VA_ARGS__)
60 
61 #define OPT_DUR(name, field, def, min, max, descr, ...) \
62  OPT_GENERIC(name, field, def, min, max, descr, DURATION, str, __VA_ARGS__)
63 
64 static const AVOption sine_options[] = {
65  OPT_DBL("frequency", frequency, 440, 0, DBL_MAX, "set the sine frequency"),
66  OPT_DBL("f", frequency, 440, 0, DBL_MAX, "set the sine frequency"),
67  OPT_DBL("beep_factor", beep_factor, 0, 0, DBL_MAX, "set the beep fequency factor"),
68  OPT_DBL("b", beep_factor, 0, 0, DBL_MAX, "set the beep fequency factor"),
69  OPT_INT("sample_rate", sample_rate, 44100, 1, INT_MAX, "set the sample rate"),
70  OPT_INT("r", sample_rate, 44100, 1, INT_MAX, "set the sample rate"),
71  OPT_DUR("duration", duration, 0, 0, INT64_MAX, "set the audio duration"),
72  OPT_DUR("d", duration, 0, 0, INT64_MAX, "set the audio duration"),
73  OPT_INT("samples_per_frame", samples_per_frame, 1024, 0, INT_MAX, "set the number of samples per frame"),
74  {NULL}
75 };
76 
78 
79 #define LOG_PERIOD 15
80 #define AMPLITUDE 4095
81 #define AMPLITUDE_SHIFT 3
82 
83 static void make_sin_table(int16_t *sin)
84 {
85  unsigned half_pi = 1 << (LOG_PERIOD - 2);
86  unsigned ampls = AMPLITUDE << AMPLITUDE_SHIFT;
87  uint64_t unit2 = (uint64_t)(ampls * ampls) << 32;
88  unsigned step, i, c, s, k, new_k, n2;
89 
90  /* Principle: if u = exp(i*a1) and v = exp(i*a2), then
91  exp(i*(a1+a2)/2) = (u+v) / length(u+v) */
92  sin[0] = 0;
93  sin[half_pi] = ampls;
94  for (step = half_pi; step > 1; step /= 2) {
95  /* k = (1 << 16) * amplitude / length(u+v)
96  In exact values, k is constant at a given step */
97  k = 0x10000;
98  for (i = 0; i < half_pi / 2; i += step) {
99  s = sin[i] + sin[i + step];
100  c = sin[half_pi - i] + sin[half_pi - i - step];
101  n2 = s * s + c * c;
102  /* Newton's method to solve n² * k² = unit² */
103  while (1) {
104  new_k = (k + unit2 / ((uint64_t)k * n2) + 1) >> 1;
105  if (k == new_k)
106  break;
107  k = new_k;
108  }
109  sin[i + step / 2] = (k * s + 0x7FFF) >> 16;
110  sin[half_pi - i - step / 2] = (k * c + 0x8000) >> 16;
111  }
112  }
113  /* Unshift amplitude */
114  for (i = 0; i <= half_pi; i++)
115  sin[i] = (sin[i] + (1 << (AMPLITUDE_SHIFT - 1))) >> AMPLITUDE_SHIFT;
116  /* Use symmetries to fill the other three quarters */
117  for (i = 0; i < half_pi; i++)
118  sin[half_pi * 2 - i] = sin[i];
119  for (i = 0; i < 2 * half_pi; i++)
120  sin[i + 2 * half_pi] = -sin[i];
121 }
122 
123 static av_cold int init(AVFilterContext *ctx)
124 {
125  SineContext *sine = ctx->priv;
126 
127  if (!(sine->sin = av_malloc(sizeof(*sine->sin) << LOG_PERIOD)))
128  return AVERROR(ENOMEM);
129  sine->dphi = ldexp(sine->frequency, 32) / sine->sample_rate + 0.5;
130  make_sin_table(sine->sin);
131 
132  if (sine->beep_factor) {
133  sine->beep_period = sine->sample_rate;
134  sine->beep_length = sine->beep_period / 25;
135  sine->dphi_beep = ldexp(sine->beep_factor * sine->frequency, 32) /
136  sine->sample_rate + 0.5;
137  }
138 
139  return 0;
140 }
141 
142 static av_cold void uninit(AVFilterContext *ctx)
143 {
144  SineContext *sine = ctx->priv;
145 
146  av_freep(&sine->sin);
147 }
148 
150 {
151  SineContext *sine = ctx->priv;
152  static const int64_t chlayouts[] = { AV_CH_LAYOUT_MONO, -1 };
153  int sample_rates[] = { sine->sample_rate, -1 };
154  static const enum AVSampleFormat sample_fmts[] = { AV_SAMPLE_FMT_S16,
156 
157  ff_set_common_formats (ctx, ff_make_format_list(sample_fmts));
160  return 0;
161 }
162 
163 static av_cold int config_props(AVFilterLink *outlink)
164 {
165  SineContext *sine = outlink->src->priv;
166  sine->duration = av_rescale(sine->duration, sine->sample_rate, AV_TIME_BASE);
167  return 0;
168 }
169 
170 static int request_frame(AVFilterLink *outlink)
171 {
172  SineContext *sine = outlink->src->priv;
173  AVFrame *frame;
174  int i, nb_samples = sine->samples_per_frame;
175  int16_t *samples;
176 
177  if (sine->duration) {
178  nb_samples = FFMIN(nb_samples, sine->duration - sine->pts);
179  av_assert1(nb_samples >= 0);
180  if (!nb_samples)
181  return AVERROR_EOF;
182  }
183  if (!(frame = ff_get_audio_buffer(outlink, nb_samples)))
184  return AVERROR(ENOMEM);
185  samples = (int16_t *)frame->data[0];
186 
187  for (i = 0; i < nb_samples; i++) {
188  samples[i] = sine->sin[sine->phi >> (32 - LOG_PERIOD)];
189  sine->phi += sine->dphi;
190  if (sine->beep_index < sine->beep_length) {
191  samples[i] += sine->sin[sine->phi_beep >> (32 - LOG_PERIOD)] << 1;
192  sine->phi_beep += sine->dphi_beep;
193  }
194  if (++sine->beep_index == sine->beep_period)
195  sine->beep_index = 0;
196  }
197 
198  frame->pts = sine->pts;
199  sine->pts += nb_samples;
200  return ff_filter_frame(outlink, frame);
201 }
202 
203 static const AVFilterPad sine_outputs[] = {
204  {
205  .name = "default",
206  .type = AVMEDIA_TYPE_AUDIO,
207  .request_frame = request_frame,
208  .config_props = config_props,
209  },
210  { NULL }
211 };
212 
214  .name = "sine",
215  .description = NULL_IF_CONFIG_SMALL("Generate sine wave audio signal."),
216  .query_formats = query_formats,
217  .init = init,
218  .uninit = uninit,
219  .priv_size = sizeof(SineContext),
220  .inputs = NULL,
221  .outputs = sine_outputs,
222  .priv_class = &sine_class,
223 };