2 * Copyright (c) 2012 Clément Bœsch <ubitux@gmail.com>
4 * This file is part of FFmpeg.
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.
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.
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
23 * Audio silence detector
26 #include "libavutil/opt.h"
27 #include "libavutil/timestamp.h"
34 char *noise_str; ///< noise option string
35 double noise; ///< noise amplitude ratio
36 int duration; ///< minimum duration of silence until notification
37 int64_t nb_null_samples; ///< current number of continuous zero samples
38 int64_t start; ///< if silence is detected, this value contains the time of the first zero sample
39 int last_sample_rate; ///< last sample rate to check for sample rate changes
40 } SilenceDetectContext;
42 #define OFFSET(x) offsetof(SilenceDetectContext, x)
43 static const AVOption silencedetect_options[] = {
44 { "n", "set noise tolerance", OFFSET(noise_str), AV_OPT_TYPE_STRING, {.str="-60dB"}, CHAR_MIN, CHAR_MAX },
45 { "noise", "set noise tolerance", OFFSET(noise_str), AV_OPT_TYPE_STRING, {.str="-60dB"}, CHAR_MIN, CHAR_MAX },
46 { "d", "set minimum duration in seconds", OFFSET(duration), AV_OPT_TYPE_INT, {.dbl=2}, 0, INT_MAX},
47 { "duration", "set minimum duration in seconds", OFFSET(duration), AV_OPT_TYPE_INT, {.dbl=2}, 0, INT_MAX},
51 static const char *silencedetect_get_name(void *ctx)
53 return "silencedetect";
56 static const AVClass silencedetect_class = {
57 .class_name = "SilenceDetectContext",
58 .item_name = silencedetect_get_name,
59 .option = silencedetect_options,
62 static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
66 SilenceDetectContext *silence = ctx->priv;
68 silence->class = &silencedetect_class;
69 av_opt_set_defaults(silence);
71 if ((ret = av_set_options_string(silence, args, "=", ":")) < 0) {
72 av_log(ctx, AV_LOG_ERROR, "Error parsing options string: '%s'\n", args);
76 silence->noise = strtod(silence->noise_str, &tail);
77 if (!strcmp(tail, "dB")) {
78 silence->noise = pow(10, silence->noise/20);
80 av_log(ctx, AV_LOG_ERROR, "Invalid value '%s' for noise parameter.\n",
82 return AVERROR(EINVAL);
88 static void filter_samples(AVFilterLink *inlink, AVFilterBufferRef *insamples)
91 SilenceDetectContext *silence = inlink->dst->priv;
92 const int nb_channels = av_get_channel_layout_nb_channels(inlink->channel_layout);
93 const int srate = inlink->sample_rate;
94 const int nb_samples = insamples->audio->nb_samples * nb_channels;
95 const int64_t nb_samples_notify = srate * silence->duration * nb_channels;
97 // scale number of null samples to the new sample rate
98 if (silence->last_sample_rate && silence->last_sample_rate != srate)
99 silence->nb_null_samples =
100 srate * silence->nb_null_samples / silence->last_sample_rate;
101 silence->last_sample_rate = srate;
103 // TODO: support more sample formats
104 if (insamples->format == AV_SAMPLE_FMT_DBL) {
105 double *p = (double *)insamples->data[0];
107 for (i = 0; i < nb_samples; i++, p++) {
108 if (*p < silence->noise && *p > -silence->noise) {
109 if (!silence->start) {
110 silence->nb_null_samples++;
111 if (silence->nb_null_samples >= nb_samples_notify) {
112 silence->start = insamples->pts - silence->duration / av_q2d(inlink->time_base);
113 av_log(silence, AV_LOG_INFO,
114 "silence_start: %s\n", av_ts2timestr(silence->start, &inlink->time_base));
119 av_log(silence, AV_LOG_INFO,
120 "silence_end: %s | silence_duration: %s\n",
121 av_ts2timestr(insamples->pts, &inlink->time_base),
122 av_ts2timestr(insamples->pts - silence->start, &inlink->time_base));
123 silence->nb_null_samples = silence->start = 0;
128 ff_filter_samples(inlink->dst->outputs[0], insamples);
131 static int query_formats(AVFilterContext *ctx)
133 AVFilterFormats *formats = NULL;
134 AVFilterChannelLayouts *layouts = NULL;
135 enum AVSampleFormat sample_fmts[] = {
140 layouts = ff_all_channel_layouts();
142 return AVERROR(ENOMEM);
143 ff_set_common_channel_layouts(ctx, layouts);
145 formats = avfilter_make_format_list(sample_fmts);
147 return AVERROR(ENOMEM);
148 avfilter_set_common_sample_formats(ctx, formats);
150 formats = ff_all_samplerates();
152 return AVERROR(ENOMEM);
153 ff_set_common_samplerates(ctx, formats);
158 AVFilter avfilter_af_silencedetect = {
159 .name = "silencedetect",
160 .description = NULL_IF_CONFIG_SMALL("Detect silence."),
161 .priv_size = sizeof(SilenceDetectContext),
163 .query_formats = query_formats,
165 .inputs = (const AVFilterPad[]) {
167 .type = AVMEDIA_TYPE_AUDIO,
168 .get_audio_buffer = ff_null_get_audio_buffer,
169 .filter_samples = filter_samples, },
172 .outputs = (const AVFilterPad[]) {
174 .type = AVMEDIA_TYPE_AUDIO, },