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af_volumedetect.c
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1 /*
2  * Copyright (c) 2012 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 
22 #include "libavutil/avassert.h"
23 #include "audio.h"
24 #include "avfilter.h"
25 #include "internal.h"
26 
27 typedef struct {
28  /**
29  * Number of samples at each PCM value.
30  * histogram[0x8000 + i] is the number of samples at value i.
31  * The extra element is there for symmetry.
32  */
33  uint64_t histogram[0x10001];
35 
37 {
38  static const enum AVSampleFormat sample_fmts[] = {
42  };
44 
45  if (!(formats = ff_make_format_list(sample_fmts)))
46  return AVERROR(ENOMEM);
47  ff_set_common_formats(ctx, formats);
48 
49  return 0;
50 }
51 
53 {
54  AVFilterContext *ctx = inlink->dst;
55  VolDetectContext *vd = ctx->priv;
56  int64_t layout = samples->audio->channel_layout;
57  int nb_samples = samples->audio->nb_samples;
59  int nb_planes = nb_channels;
60  int plane, i;
61  int16_t *pcm;
62 
63  if (!av_sample_fmt_is_planar(samples->format)) {
64  nb_samples *= nb_channels;
65  nb_planes = 1;
66  }
67  for (plane = 0; plane < nb_planes; plane++) {
68  pcm = (int16_t *)samples->extended_data[plane];
69  for (i = 0; i < nb_samples; i++)
70  vd->histogram[pcm[i] + 0x8000]++;
71  }
72 
73  return ff_filter_frame(inlink->dst->outputs[0], samples);
74 }
75 
76 #define MAX_DB 91
77 
78 static inline double logdb(uint64_t v)
79 {
80  double d = v / (double)(0x8000 * 0x8000);
81  if (!v)
82  return MAX_DB;
83  return log(d) * -4.3429448190325182765112891891660508229; /* -10/log(10) */
84 }
85 
86 static void print_stats(AVFilterContext *ctx)
87 {
88  VolDetectContext *vd = ctx->priv;
89  int i, max_volume, shift;
90  uint64_t nb_samples = 0, power = 0, nb_samples_shift = 0, sum = 0;
91  uint64_t histdb[MAX_DB + 1] = { 0 };
92 
93  for (i = 0; i < 0x10000; i++)
94  nb_samples += vd->histogram[i];
95  av_log(ctx, AV_LOG_INFO, "n_samples: %"PRId64"\n", nb_samples);
96  if (!nb_samples)
97  return;
98 
99  /* If nb_samples > 1<<34, there is a risk of overflow in the
100  multiplication or the sum: shift all histogram values to avoid that.
101  The total number of samples must be recomputed to avoid rounding
102  errors. */
103  shift = av_log2(nb_samples >> 33);
104  for (i = 0; i < 0x10000; i++) {
105  nb_samples_shift += vd->histogram[i] >> shift;
106  power += (i - 0x8000) * (i - 0x8000) * (vd->histogram[i] >> shift);
107  }
108  if (!nb_samples_shift)
109  return;
110  power = (power + nb_samples_shift / 2) / nb_samples_shift;
111  av_assert0(power <= 0x8000 * 0x8000);
112  av_log(ctx, AV_LOG_INFO, "mean_volume: %.1f dB\n", -logdb(power));
113 
114  max_volume = 0x8000;
115  while (max_volume > 0 && !vd->histogram[0x8000 + max_volume] &&
116  !vd->histogram[0x8000 - max_volume])
117  max_volume--;
118  av_log(ctx, AV_LOG_INFO, "max_volume: %.1f dB\n", -logdb(max_volume * max_volume));
119 
120  for (i = 0; i < 0x10000; i++)
121  histdb[(int)logdb((i - 0x8000) * (i - 0x8000))] += vd->histogram[i];
122  for (i = 0; i <= MAX_DB && !histdb[i]; i++);
123  for (; i <= MAX_DB && sum < nb_samples / 1000; i++) {
124  av_log(ctx, AV_LOG_INFO, "histogram_%ddb: %"PRId64"\n", i, histdb[i]);
125  sum += histdb[i];
126  }
127 }
128 
129 static void uninit(AVFilterContext *ctx)
130 {
131  print_stats(ctx);
132 }
133 
135  {
136  .name = "default",
137  .type = AVMEDIA_TYPE_AUDIO,
138  .get_audio_buffer = ff_null_get_audio_buffer,
139  .filter_frame = filter_frame,
140  .min_perms = AV_PERM_READ,
141  },
142  { NULL }
143 };
144 
146  {
147  .name = "default",
148  .type = AVMEDIA_TYPE_AUDIO,
149  },
150  { NULL }
151 };
152 
154  .name = "volumedetect",
155  .description = NULL_IF_CONFIG_SMALL("Detect audio volume."),
156 
157  .priv_size = sizeof(VolDetectContext),
159  .uninit = uninit,
160  .inputs = volumedetect_inputs,
161  .outputs = volumedetect_outputs,
162 };