1 /*
2 * Copyright (c) 2013-2020 Michael Barbour <barbour.michael.0@gmail.com>
3 * Copyright (c) 2021 Paul B Mahol
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 #include "libavutil/channel_layout.h"
23 #include "libavutil/ffmath.h"
24 #include "libavutil/lfg.h"
25 #include "libavutil/random_seed.h"
26 #include "libavutil/opt.h"
27 #include "avfilter.h"
28 #include "audio.h"
29 #include "formats.h"
30
31 #define MAX_STAGES 16
32 #define FILTER_FC 1100.0
33 #define RT60_LF 0.1
34 #define RT60_HF 0.008
35
36 typedef struct APContext {
37 int len, p;
38 double *mx, *my;
39 double b0, b1, a0, a1;
40 } APContext;
41
42 typedef struct ADecorrelateContext {
43 const AVClass *class;
44
45 int stages;
46 int64_t seed;
47
48 int nb_channels;
49 APContext (*ap)[MAX_STAGES];
50
51 AVLFG c;
52
53 void (*filter_channel)(AVFilterContext *ctx,
54 int channel,
55 AVFrame *in, AVFrame *out);
56 } ADecorrelateContext;
57
ap_init(APContext * ap,int fs,double delay)58 static int ap_init(APContext *ap, int fs, double delay)
59 {
60 const int delay_samples = lrint(round(delay * fs));
61 const double gain_lf = -60.0 / (RT60_LF * fs) * delay_samples;
62 const double gain_hf = -60.0 / (RT60_HF * fs) * delay_samples;
63 const double w0 = 2.0 * M_PI * FILTER_FC / fs;
64 const double t = tan(w0 / 2.0);
65 const double g_hf = ff_exp10(gain_hf / 20.0);
66 const double gd = ff_exp10((gain_lf-gain_hf) / 20.0);
67 const double sgd = sqrt(gd);
68
69 ap->len = delay_samples + 1;
70 ap->p = 0;
71 ap->mx = av_calloc(ap->len, sizeof(*ap->mx));
72 ap->my = av_calloc(ap->len, sizeof(*ap->my));
73 if (!ap->mx || !ap->my)
74 return AVERROR(ENOMEM);
75
76 ap->a0 = t + sgd;
77 ap->a1 = (t - sgd) / ap->a0;
78 ap->b0 = (gd*t - sgd) / ap->a0 * g_hf;
79 ap->b1 = (gd*t + sgd) / ap->a0 * g_hf;
80 ap->a0 = 1.0;
81
82 return 0;
83 }
84
ap_free(APContext * ap)85 static void ap_free(APContext *ap)
86 {
87 av_freep(&ap->mx);
88 av_freep(&ap->my);
89 }
90
ap_run(APContext * ap,double x)91 static double ap_run(APContext *ap, double x)
92 {
93 const int i0 = ((ap->p < 1) ? ap->len : ap->p)-1, i_n1 = ap->p, i_n2 = (ap->p+1 >= ap->len) ? 0 : ap->p+1;
94 const double r = ap->b1*x + ap->b0*ap->mx[i0] + ap->a1*ap->mx[i_n2] + ap->a0*ap->mx[i_n1] -
95 ap->a1*ap->my[i0] - ap->b0*ap->my[i_n2] - ap->b1*ap->my[i_n1];
96
97 ap->mx[ap->p] = x;
98 ap->my[ap->p] = r;
99 ap->p = (ap->p+1 >= ap->len) ? 0 : ap->p+1;
100
101 return r;
102 }
103
filter_channel_dbl(AVFilterContext * ctx,int ch,AVFrame * in,AVFrame * out)104 static void filter_channel_dbl(AVFilterContext *ctx, int ch,
105 AVFrame *in, AVFrame *out)
106 {
107 ADecorrelateContext *s = ctx->priv;
108 const double *src = (const double *)in->extended_data[ch];
109 double *dst = (double *)out->extended_data[ch];
110 const int nb_samples = in->nb_samples;
111 const int stages = s->stages;
112 APContext *ap0 = &s->ap[ch][0];
113
114 for (int n = 0; n < nb_samples; n++) {
115 dst[n] = ap_run(ap0, src[n]);
116 for (int i = 1; i < stages; i++) {
117 APContext *ap = &s->ap[ch][i];
118
119 dst[n] = ap_run(ap, dst[n]);
120 }
121 }
122 }
123
config_input(AVFilterLink * inlink)124 static int config_input(AVFilterLink *inlink)
125 {
126 AVFilterContext *ctx = inlink->dst;
127 ADecorrelateContext *s = ctx->priv;
128 int ret;
129
130 if (s->seed == -1)
131 s->seed = av_get_random_seed();
132 av_lfg_init(&s->c, s->seed);
133
134 s->nb_channels = inlink->ch_layout.nb_channels;
135 s->ap = av_calloc(inlink->ch_layout.nb_channels, sizeof(*s->ap));
136 if (!s->ap)
137 return AVERROR(ENOMEM);
138
139 for (int i = 0; i < inlink->ch_layout.nb_channels; i++) {
140 for (int j = 0; j < s->stages; j++) {
141 ret = ap_init(&s->ap[i][j], inlink->sample_rate,
142 (double)av_lfg_get(&s->c) / 0xffffffff * 2.2917e-3 + 0.83333e-3);
143 if (ret < 0)
144 return ret;
145 }
146 }
147
148 s->filter_channel = filter_channel_dbl;
149
150 return 0;
151 }
152
153 typedef struct ThreadData {
154 AVFrame *in, *out;
155 } ThreadData;
156
filter_channels(AVFilterContext * ctx,void * arg,int jobnr,int nb_jobs)157 static int filter_channels(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs)
158 {
159 ADecorrelateContext *s = ctx->priv;
160 ThreadData *td = arg;
161 AVFrame *out = td->out;
162 AVFrame *in = td->in;
163 const int start = (in->ch_layout.nb_channels * jobnr) / nb_jobs;
164 const int end = (in->ch_layout.nb_channels * (jobnr+1)) / nb_jobs;
165
166 for (int ch = start; ch < end; ch++)
167 s->filter_channel(ctx, ch, in, out);
168
169 return 0;
170 }
171
filter_frame(AVFilterLink * inlink,AVFrame * in)172 static int filter_frame(AVFilterLink *inlink, AVFrame *in)
173 {
174 AVFilterContext *ctx = inlink->dst;
175 AVFilterLink *outlink = ctx->outputs[0];
176 AVFrame *out;
177 ThreadData td;
178
179 if (av_frame_is_writable(in)) {
180 out = in;
181 } else {
182 out = ff_get_audio_buffer(outlink, in->nb_samples);
183 if (!out) {
184 av_frame_free(&in);
185 return AVERROR(ENOMEM);
186 }
187 av_frame_copy_props(out, in);
188 }
189
190 td.in = in; td.out = out;
191 ff_filter_execute(ctx, filter_channels, &td, NULL,
192 FFMIN(inlink->ch_layout.nb_channels, ff_filter_get_nb_threads(ctx)));
193
194 if (out != in)
195 av_frame_free(&in);
196 return ff_filter_frame(outlink, out);
197 }
198
uninit(AVFilterContext * ctx)199 static av_cold void uninit(AVFilterContext *ctx)
200 {
201 ADecorrelateContext *s = ctx->priv;
202
203 if (s->ap) {
204 for (int ch = 0; ch < s->nb_channels; ch++) {
205 for (int stage = 0; stage < s->stages; stage++)
206 ap_free(&s->ap[ch][stage]);
207 }
208 }
209
210 av_freep(&s->ap);
211 }
212
213 #define OFFSET(x) offsetof(ADecorrelateContext, x)
214 #define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
215
216 static const AVOption adecorrelate_options[] = {
217 { "stages", "set filtering stages", OFFSET(stages), AV_OPT_TYPE_INT, {.i64=6}, 1, MAX_STAGES, FLAGS },
218 { "seed", "set random seed", OFFSET(seed), AV_OPT_TYPE_INT64, {.i64=-1}, -1, UINT_MAX, FLAGS },
219 { NULL }
220 };
221
222 AVFILTER_DEFINE_CLASS(adecorrelate);
223
224 static const AVFilterPad inputs[] = {
225 {
226 .name = "default",
227 .type = AVMEDIA_TYPE_AUDIO,
228 .filter_frame = filter_frame,
229 .config_props = config_input,
230 },
231 };
232
233 static const AVFilterPad outputs[] = {
234 {
235 .name = "default",
236 .type = AVMEDIA_TYPE_AUDIO,
237 },
238 };
239
240 const AVFilter ff_af_adecorrelate = {
241 .name = "adecorrelate",
242 .description = NULL_IF_CONFIG_SMALL("Apply decorrelation to input audio."),
243 .priv_size = sizeof(ADecorrelateContext),
244 .priv_class = &adecorrelate_class,
245 .uninit = uninit,
246 FILTER_INPUTS(inputs),
247 FILTER_OUTPUTS(outputs),
248 FILTER_SINGLE_SAMPLEFMT(AV_SAMPLE_FMT_DBLP),
249 .flags = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC |
250 AVFILTER_FLAG_SLICE_THREADS,
251 };
252