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path: root/libavfilter/af_aemphasis.c (plain)
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1/*
2 * Copyright (c) 2001-2010 Krzysztof Foltman, Markus Schmidt, Thor Harald Johansen, Damien Zammit and others
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
8 * License 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 GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with FFmpeg; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20
21#include "libavutil/opt.h"
22#include "avfilter.h"
23#include "internal.h"
24#include "audio.h"
25
26typedef struct BiquadCoeffs {
27 double a0, a1, a2, b1, b2;
28} BiquadCoeffs;
29
30typedef struct BiquadD2 {
31 double a0, a1, a2, b1, b2, w1, w2;
32} BiquadD2;
33
34typedef struct RIAACurve {
35 BiquadD2 r1;
36 BiquadD2 brickw;
37 int use_brickw;
38} RIAACurve;
39
40typedef struct AudioEmphasisContext {
41 const AVClass *class;
42 int mode, type;
43 double level_in, level_out;
44
45 RIAACurve *rc;
46} AudioEmphasisContext;
47
48#define OFFSET(x) offsetof(AudioEmphasisContext, x)
49#define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
50
51static const AVOption aemphasis_options[] = {
52 { "level_in", "set input gain", OFFSET(level_in), AV_OPT_TYPE_DOUBLE, {.dbl=1}, 0, 64, FLAGS },
53 { "level_out", "set output gain", OFFSET(level_out), AV_OPT_TYPE_DOUBLE, {.dbl=1}, 0, 64, FLAGS },
54 { "mode", "set filter mode", OFFSET(mode), AV_OPT_TYPE_INT, {.i64=0}, 0, 1, FLAGS, "mode" },
55 { "reproduction", NULL, 0, AV_OPT_TYPE_CONST, {.i64=0}, 0, 0, FLAGS, "mode" },
56 { "production", NULL, 0, AV_OPT_TYPE_CONST, {.i64=1}, 0, 0, FLAGS, "mode" },
57 { "type", "set filter type", OFFSET(type), AV_OPT_TYPE_INT, {.i64=4}, 0, 8, FLAGS, "type" },
58 { "col", "Columbia", 0, AV_OPT_TYPE_CONST, {.i64=0}, 0, 0, FLAGS, "type" },
59 { "emi", "EMI", 0, AV_OPT_TYPE_CONST, {.i64=1}, 0, 0, FLAGS, "type" },
60 { "bsi", "BSI (78RPM)", 0, AV_OPT_TYPE_CONST, {.i64=2}, 0, 0, FLAGS, "type" },
61 { "riaa", "RIAA", 0, AV_OPT_TYPE_CONST, {.i64=3}, 0, 0, FLAGS, "type" },
62 { "cd", "Compact Disc (CD)", 0, AV_OPT_TYPE_CONST, {.i64=4}, 0, 0, FLAGS, "type" },
63 { "50fm", "50µs (FM)", 0, AV_OPT_TYPE_CONST, {.i64=5}, 0, 0, FLAGS, "type" },
64 { "75fm", "75µs (FM)", 0, AV_OPT_TYPE_CONST, {.i64=6}, 0, 0, FLAGS, "type" },
65 { "50kf", "50µs (FM-KF)", 0, AV_OPT_TYPE_CONST, {.i64=7}, 0, 0, FLAGS, "type" },
66 { "75kf", "75µs (FM-KF)", 0, AV_OPT_TYPE_CONST, {.i64=8}, 0, 0, FLAGS, "type" },
67 { NULL }
68};
69
70AVFILTER_DEFINE_CLASS(aemphasis);
71
72static inline double biquad(BiquadD2 *bq, double in)
73{
74 double n = in;
75 double tmp = n - bq->w1 * bq->b1 - bq->w2 * bq->b2;
76 double out = tmp * bq->a0 + bq->w1 * bq->a1 + bq->w2 * bq->a2;
77
78 bq->w2 = bq->w1;
79 bq->w1 = tmp;
80
81 return out;
82}
83
84static int filter_frame(AVFilterLink *inlink, AVFrame *in)
85{
86 AVFilterContext *ctx = inlink->dst;
87 AVFilterLink *outlink = ctx->outputs[0];
88 AudioEmphasisContext *s = ctx->priv;
89 const double *src = (const double *)in->data[0];
90 const double level_out = s->level_out;
91 const double level_in = s->level_in;
92 AVFrame *out;
93 double *dst;
94 int n, c;
95
96 if (av_frame_is_writable(in)) {
97 out = in;
98 } else {
99 out = ff_get_audio_buffer(inlink, in->nb_samples);
100 if (!out) {
101 av_frame_free(&in);
102 return AVERROR(ENOMEM);
103 }
104 av_frame_copy_props(out, in);
105 }
106 dst = (double *)out->data[0];
107
108 for (n = 0; n < in->nb_samples; n++) {
109 for (c = 0; c < inlink->channels; c++)
110 dst[c] = level_out * biquad(&s->rc[c].r1, s->rc[c].use_brickw ? biquad(&s->rc[c].brickw, src[c] * level_in) : src[c] * level_in);
111 dst += inlink->channels;
112 src += inlink->channels;
113 }
114
115 if (in != out)
116 av_frame_free(&in);
117 return ff_filter_frame(outlink, out);
118}
119
120static int query_formats(AVFilterContext *ctx)
121{
122 AVFilterChannelLayouts *layouts;
123 AVFilterFormats *formats;
124 static const enum AVSampleFormat sample_fmts[] = {
125 AV_SAMPLE_FMT_DBL,
126 AV_SAMPLE_FMT_NONE
127 };
128 int ret;
129
130 layouts = ff_all_channel_counts();
131 if (!layouts)
132 return AVERROR(ENOMEM);
133 ret = ff_set_common_channel_layouts(ctx, layouts);
134 if (ret < 0)
135 return ret;
136
137 formats = ff_make_format_list(sample_fmts);
138 if (!formats)
139 return AVERROR(ENOMEM);
140 ret = ff_set_common_formats(ctx, formats);
141 if (ret < 0)
142 return ret;
143
144 formats = ff_all_samplerates();
145 if (!formats)
146 return AVERROR(ENOMEM);
147 return ff_set_common_samplerates(ctx, formats);
148}
149
150static inline void set_highshelf_rbj(BiquadD2 *bq, double freq, double q, double peak, double sr)
151{
152 double A = sqrt(peak);
153 double w0 = freq * 2 * M_PI / sr;
154 double alpha = sin(w0) / (2 * q);
155 double cw0 = cos(w0);
156 double tmp = 2 * sqrt(A) * alpha;
157 double b0 = 0, ib0 = 0;
158
159 bq->a0 = A*( (A+1) + (A-1)*cw0 + tmp);
160 bq->a1 = -2*A*( (A-1) + (A+1)*cw0);
161 bq->a2 = A*( (A+1) + (A-1)*cw0 - tmp);
162 b0 = (A+1) - (A-1)*cw0 + tmp;
163 bq->b1 = 2*( (A-1) - (A+1)*cw0);
164 bq->b2 = (A+1) - (A-1)*cw0 - tmp;
165
166 ib0 = 1 / b0;
167 bq->b1 *= ib0;
168 bq->b2 *= ib0;
169 bq->a0 *= ib0;
170 bq->a1 *= ib0;
171 bq->a2 *= ib0;
172}
173
174static inline void set_lp_rbj(BiquadD2 *bq, double fc, double q, double sr, double gain)
175{
176 double omega = 2.0 * M_PI * fc / sr;
177 double sn = sin(omega);
178 double cs = cos(omega);
179 double alpha = sn/(2 * q);
180 double inv = 1.0/(1.0 + alpha);
181
182 bq->a2 = bq->a0 = gain * inv * (1.0 - cs) * 0.5;
183 bq->a1 = bq->a0 + bq->a0;
184 bq->b1 = (-2.0 * cs * inv);
185 bq->b2 = ((1.0 - alpha) * inv);
186}
187
188static double freq_gain(BiquadCoeffs *c, double freq, double sr)
189{
190 double zr, zi;
191
192 freq *= 2.0 * M_PI / sr;
193 zr = cos(freq);
194 zi = -sin(freq);
195
196 /* |(a0 + a1*z + a2*z^2)/(1 + b1*z + b2*z^2)| */
197 return hypot(c->a0 + c->a1*zr + c->a2*(zr*zr-zi*zi), c->a1*zi + 2*c->a2*zr*zi) /
198 hypot(1 + c->b1*zr + c->b2*(zr*zr-zi*zi), c->b1*zi + 2*c->b2*zr*zi);
199}
200
201static int config_input(AVFilterLink *inlink)
202{
203 double i, j, k, g, t, a0, a1, a2, b1, b2, tau1, tau2, tau3;
204 double cutfreq, gain1kHz, gc, sr = inlink->sample_rate;
205 AVFilterContext *ctx = inlink->dst;
206 AudioEmphasisContext *s = ctx->priv;
207 BiquadCoeffs coeffs;
208 int ch;
209
210 s->rc = av_calloc(inlink->channels, sizeof(*s->rc));
211 if (!s->rc)
212 return AVERROR(ENOMEM);
213
214 switch (s->type) {
215 case 0: //"Columbia"
216 i = 100.;
217 j = 500.;
218 k = 1590.;
219 break;
220 case 1: //"EMI"
221 i = 70.;
222 j = 500.;
223 k = 2500.;
224 break;
225 case 2: //"BSI(78rpm)"
226 i = 50.;
227 j = 353.;
228 k = 3180.;
229 break;
230 case 3: //"RIAA"
231 default:
232 tau1 = 0.003180;
233 tau2 = 0.000318;
234 tau3 = 0.000075;
235 i = 1. / (2. * M_PI * tau1);
236 j = 1. / (2. * M_PI * tau2);
237 k = 1. / (2. * M_PI * tau3);
238 break;
239 case 4: //"CD Mastering"
240 tau1 = 0.000050;
241 tau2 = 0.000015;
242 tau3 = 0.0000001;// 1.6MHz out of audible range for null impact
243 i = 1. / (2. * M_PI * tau1);
244 j = 1. / (2. * M_PI * tau2);
245 k = 1. / (2. * M_PI * tau3);
246 break;
247 case 5: //"50µs FM (Europe)"
248 tau1 = 0.000050;
249 tau2 = tau1 / 20;// not used
250 tau3 = tau1 / 50;//
251 i = 1. / (2. * M_PI * tau1);
252 j = 1. / (2. * M_PI * tau2);
253 k = 1. / (2. * M_PI * tau3);
254 break;
255 case 6: //"75µs FM (US)"
256 tau1 = 0.000075;
257 tau2 = tau1 / 20;// not used
258 tau3 = tau1 / 50;//
259 i = 1. / (2. * M_PI * tau1);
260 j = 1. / (2. * M_PI * tau2);
261 k = 1. / (2. * M_PI * tau3);
262 break;
263 }
264
265 i *= 2 * M_PI;
266 j *= 2 * M_PI;
267 k *= 2 * M_PI;
268
269 t = 1. / sr;
270
271 //swap a1 b1, a2 b2
272 if (s->type == 7 || s->type == 8) {
273 double tau = (s->type == 7 ? 0.000050 : 0.000075);
274 double f = 1.0 / (2 * M_PI * tau);
275 double nyq = sr * 0.5;
276 double gain = sqrt(1.0 + nyq * nyq / (f * f)); // gain at Nyquist
277 double cfreq = sqrt((gain - 1.0) * f * f); // frequency
278 double q = 1.0;
279
280 if (s->type == 8)
281 q = pow((sr / 3269.0) + 19.5, -0.25); // somewhat poor curve-fit
282 if (s->type == 7)
283 q = pow((sr / 4750.0) + 19.5, -0.25);
284 if (s->mode == 0)
285 set_highshelf_rbj(&s->rc[0].r1, cfreq, q, 1. / gain, sr);
286 else
287 set_highshelf_rbj(&s->rc[0].r1, cfreq, q, gain, sr);
288 s->rc[0].use_brickw = 0;
289 } else {
290 s->rc[0].use_brickw = 1;
291 if (s->mode == 0) { // Reproduction
292 g = 1. / (4.+2.*i*t+2.*k*t+i*k*t*t);
293 a0 = (2.*t+j*t*t)*g;
294 a1 = (2.*j*t*t)*g;
295 a2 = (-2.*t+j*t*t)*g;
296 b1 = (-8.+2.*i*k*t*t)*g;
297 b2 = (4.-2.*i*t-2.*k*t+i*k*t*t)*g;
298 } else { // Production
299 g = 1. / (2.*t+j*t*t);
300 a0 = (4.+2.*i*t+2.*k*t+i*k*t*t)*g;
301 a1 = (-8.+2.*i*k*t*t)*g;
302 a2 = (4.-2.*i*t-2.*k*t+i*k*t*t)*g;
303 b1 = (2.*j*t*t)*g;
304 b2 = (-2.*t+j*t*t)*g;
305 }
306
307 coeffs.a0 = a0;
308 coeffs.a1 = a1;
309 coeffs.a2 = a2;
310 coeffs.b1 = b1;
311 coeffs.b2 = b2;
312
313 // the coeffs above give non-normalized value, so it should be normalized to produce 0dB at 1 kHz
314 // find actual gain
315 // Note: for FM emphasis, use 100 Hz for normalization instead
316 gain1kHz = freq_gain(&coeffs, 1000.0, sr);
317 // divide one filter's x[n-m] coefficients by that value
318 gc = 1.0 / gain1kHz;
319 s->rc[0].r1.a0 = coeffs.a0 * gc;
320 s->rc[0].r1.a1 = coeffs.a1 * gc;
321 s->rc[0].r1.a2 = coeffs.a2 * gc;
322 s->rc[0].r1.b1 = coeffs.b1;
323 s->rc[0].r1.b2 = coeffs.b2;
324 }
325
326 cutfreq = FFMIN(0.45 * sr, 21000.);
327 set_lp_rbj(&s->rc[0].brickw, cutfreq, 0.707, sr, 1.);
328
329 for (ch = 1; ch < inlink->channels; ch++) {
330 memcpy(&s->rc[ch], &s->rc[0], sizeof(RIAACurve));
331 }
332
333 return 0;
334}
335
336static av_cold void uninit(AVFilterContext *ctx)
337{
338 AudioEmphasisContext *s = ctx->priv;
339 av_freep(&s->rc);
340}
341
342static const AVFilterPad avfilter_af_aemphasis_inputs[] = {
343 {
344 .name = "default",
345 .type = AVMEDIA_TYPE_AUDIO,
346 .config_props = config_input,
347 .filter_frame = filter_frame,
348 },
349 { NULL }
350};
351
352static const AVFilterPad avfilter_af_aemphasis_outputs[] = {
353 {
354 .name = "default",
355 .type = AVMEDIA_TYPE_AUDIO,
356 },
357 { NULL }
358};
359
360AVFilter ff_af_aemphasis = {
361 .name = "aemphasis",
362 .description = NULL_IF_CONFIG_SMALL("Audio emphasis."),
363 .priv_size = sizeof(AudioEmphasisContext),
364 .priv_class = &aemphasis_class,
365 .uninit = uninit,
366 .query_formats = query_formats,
367 .inputs = avfilter_af_aemphasis_inputs,
368 .outputs = avfilter_af_aemphasis_outputs,
369};
370
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