[FFmpeg-devel] [PATCH 2/2] lavfi: add audio silencedetect filter.

Clément Bœsch ubitux at gmail.com
Sat Jan 7 23:05:03 CET 2012


On Sat, Jan 07, 2012 at 09:37:09PM +0100, Stefano Sabatini wrote:
> On date Saturday 2012-01-07 15:41:05 +0100, Clément Bœsch encoded:
> > On Thu, Jan 05, 2012 at 08:29:35PM +0100, Nicolas George wrote:
> [...]
> > From 2e7c6e75d225818b0eacf29f5599dfd308804406 Mon Sep 17 00:00:00 2001
> > From: =?UTF-8?q?Cl=C3=A9ment=20B=C5=93sch?= <ubitux at gmail.com>
> > Date: Tue, 3 Jan 2012 23:47:09 +0100
> > Subject: [PATCH] lavfi: add audio silencedetect filter.
> > 
> > ---
> >  Changelog                      |    1 +
> >  doc/filters.texi               |   24 ++++++
> >  libavfilter/Makefile           |    1 +
> >  libavfilter/af_silencedetect.c |  171 ++++++++++++++++++++++++++++++++++++++++
> >  libavfilter/allfilters.c       |    1 +
> >  libavfilter/avfilter.h         |    4 +-
> >  6 files changed, 200 insertions(+), 2 deletions(-)
> >  create mode 100644 libavfilter/af_silencedetect.c
> > 
> > diff --git a/Changelog b/Changelog
> > index db4c7b3..d4ec698 100644
> > --- a/Changelog
> > +++ b/Changelog
> > @@ -19,6 +19,7 @@ version next:
> >  - Avid 1:1 10-bit RGB Packer decoder
> >  - v308 Quicktime Uncompressed 4:4:4 encoder and decoder
> >  - yuv4 libquicktime packed 4:2:0 encoder and decoder
> > +- silencedetect audio filter
> >  
> >  
> >  version 0.9:
> > diff --git a/doc/filters.texi b/doc/filters.texi
> > index de73e3f..3bc117c 100644
> > --- a/doc/filters.texi
> > +++ b/doc/filters.texi
> > @@ -358,6 +358,30 @@ Note that @command{ffmpeg} integrates a default down-mix (and up-mix) system
> >  that should be preferred (see "-ac" option) unless you have very specific
> >  needs.
> >  
> > + at section silencedetect
> > +
> > +Print a notification line when silence is detected, or when sound is back in
> > +the given audio stream.
> 
> This needs more explanation. For example:
> 
> This filter logs a message when detect that the input audio volume is
> less or equal to the noise tolerance value set with @option{noise} for
> a duration greater or equal to the silence duration value set with
> @option{duration}.
> 

Thank you, you saved me :)

I just changed the "when detect that" into "when it detects that", I
think it's better (correct me if I'm wrong).

> > +
> > + at table @option
> > + at item d, duration
> > +Set silence duration until notification (default is 2 seconds).
> > +
> > + at item noise, n
> > +Set noise tolerance. Can be specified in dB or amplitude ratio. Default is
> 
> in db (in case "dB" is appended to the specified value).
> 

Added.

[...]
> > +    silence->noise = strtod(silence->noise_str, &tail);
> > +    if (!strcmp(tail, "dB"))
> > +        silence->noise = pow(10, silence->noise/20);
> 
> Alternatively you may want to create an internal function, to share
> with af_volume(). Also this is missing a check, in case noise_str
> contains a foobar value.
> 

I think it can be exported later; I added a check for invalid input.

> > +    return 0;
> > +}
> > +
> > +static void filter_samples(AVFilterLink *inlink, AVFilterBufferRef *insamples)
> > +{
> > +    int i;
> > +    SilenceDetectContext *silence = inlink->dst->priv;
> > +    const int     nb_channels       = av_get_channel_layout_nb_channels(inlink->channel_layout);
> > +    const int     nb_samples        = insamples->audio->nb_samples            * nb_channels;
> 
> > +    const int64_t nb_samples_notify = inlink->sample_rate * silence->duration * nb_channels;
> 
> alternatively you can cache nb_samples_notify, and update it when
> sample_rate changes.
> 

Mmh, instead I choose to scale nb_null_samples when the sample rate
changes...

> > +
> > +    if (silence->last_sample_rate &&
> > +        silence->last_sample_rate != inlink->sample_rate) {
> > +        av_log(silence, AV_LOG_WARNING,
> > +               "Sample rate changed, detection might not be accurate\n");
> > +        silence->start = silence->nb_null_samples = 0;
> > +    }
> > +    silence->last_sample_rate = inlink->sample_rate;
> > +
> > +    // TODO: support more sample formats
> > +    if (insamples->format == AV_SAMPLE_FMT_DBL) {
> > +        double *p = (double *)insamples->data[0];
> > +
> > +        for (i = 0; i < nb_samples; i++, p++) {
> > +            if (*p < silence->noise && *p > -silence->noise) {
> > +                if (!silence->start) {
> > +                    silence->nb_null_samples++;
> > +                    if (silence->nb_null_samples == nb_samples_notify) {

...and thus changed that condition into >= in case the scaling fails for
some reason (overflow or approximation I guess).

> > +                        silence->start = insamples->pts * av_q2d(inlink->time_base) - silence->duration;
> 
> > +                        av_log(silence, AV_LOG_INFO,
> > +                               "Silence detected at %f sec\n", silence->start);
> 
> what about "silence_start:%f"
> => easier to grep
> 

Good idea. Since the "sec" is dropped, documentation has been updated.

> > +                    }
> > +                }
> > +            } else {
> > +                if (silence->start) {
> > +                    double end = insamples->pts * av_q2d(inlink->time_base);
> > +                    av_log(silence, AV_LOG_INFO,
> > +                           "Silence ended at %f sec (duration: %f sec)\n",
> 
> same here:
> "silence_end:%f silence_duration:%s"
> 

Done.

-- 
Clément B.
-------------- next part --------------
From 012f61f5f3c4e518332cbe6f3f8e9a9a8d1d923e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20B=C5=93sch?= <ubitux at gmail.com>
Date: Tue, 3 Jan 2012 23:47:09 +0100
Subject: [PATCH] lavfi: add audio silencedetect filter.

---
 Changelog                      |    1 +
 doc/filters.texi               |   27 ++++++
 libavfilter/Makefile           |    1 +
 libavfilter/af_silencedetect.c |  175 ++++++++++++++++++++++++++++++++++++++++
 libavfilter/allfilters.c       |    1 +
 libavfilter/avfilter.h         |    4 +-
 6 files changed, 207 insertions(+), 2 deletions(-)
 create mode 100644 libavfilter/af_silencedetect.c

diff --git a/Changelog b/Changelog
index db4c7b3..d4ec698 100644
--- a/Changelog
+++ b/Changelog
@@ -19,6 +19,7 @@ version next:
 - Avid 1:1 10-bit RGB Packer decoder
 - v308 Quicktime Uncompressed 4:4:4 encoder and decoder
 - yuv4 libquicktime packed 4:2:0 encoder and decoder
+- silencedetect audio filter
 
 
 version 0.9:
diff --git a/doc/filters.texi b/doc/filters.texi
index de73e3f..279d238 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -358,6 +358,33 @@ Note that @command{ffmpeg} integrates a default down-mix (and up-mix) system
 that should be preferred (see "-ac" option) unless you have very specific
 needs.
 
+ at section silencedetect
+
+This filter logs a message when it detects that the input audio volume is less
+or equal to the noise tolerance value set with @option{noise} for a duration
+greater or equal to the silence duration value set with @option{duration}. The
+printed times and duration are expressed in seconds.
+
+ at table @option
+ at item duration, d
+Set silence duration until notification (default is 2 seconds).
+
+ at item noise, n
+Set noise tolerance. Can be specified in dB (in case "dB" is appended to the
+specified value) or amplitude ratio. Default is -60dB, or 0.001.
+ at end table
+
+Detect 5 seconds of silence with -50dB noise tolerance:
+ at example
+silencedetect=n=-50dB:d=5
+ at end example
+
+Complete example with @command{ffmpeg} to detect silence with 0.0001 noise
+tolerance in @file{silence.mp3}:
+ at example
+ffmpeg -f lavfi -i amovie=silence.mp3,silencedetect=noise=0.0001 -f null -
+ at end example
+
 @section volume
 
 Adjust the input audio volume.
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 0d8f120..bb5748b 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -35,6 +35,7 @@ OBJS-$(CONFIG_ASTREAMSYNC_FILTER)            += af_astreamsync.o
 OBJS-$(CONFIG_EARWAX_FILTER)                 += af_earwax.o
 OBJS-$(CONFIG_PAN_FILTER)                    += af_pan.o
 OBJS-$(CONFIG_VOLUME_FILTER)                 += af_volume.o
+OBJS-$(CONFIG_SILENCEDETECT_FILTER)          += af_silencedetect.o
 
 OBJS-$(CONFIG_ABUFFER_FILTER)                += asrc_abuffer.o
 OBJS-$(CONFIG_AEVALSRC_FILTER)               += asrc_aevalsrc.o
diff --git a/libavfilter/af_silencedetect.c b/libavfilter/af_silencedetect.c
new file mode 100644
index 0000000..db606a7
--- /dev/null
+++ b/libavfilter/af_silencedetect.c
@@ -0,0 +1,175 @@
+/*
+ * Copyright (c) 2012 Clément Bœsch <ubitux at gmail.com>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * Audio silence detector
+ */
+
+#include "libavutil/opt.h"
+#include "avfilter.h"
+
+typedef struct {
+    const AVClass *class;
+    char *noise_str;            ///< noise option string
+    double noise;               ///< noise amplitude ratio
+    int duration;               ///< minimum duration to monitor in seconds
+    int64_t nb_null_samples;    ///< current number of continuous zero samples
+    double start;               ///< if silence is detected, this value contains the time of the first zero sample
+    int last_sample_rate;       ///< last sample rate to check for sample rate changes
+} SilenceDetectContext;
+
+#define OFFSET(x) offsetof(SilenceDetectContext, x)
+static const AVOption silencedetect_options[] = {
+    { "n",         "set noise tolerance",              OFFSET(noise_str), AV_OPT_TYPE_STRING, {.str="-60dB"}, CHAR_MIN, CHAR_MAX },
+    { "noise",     "set noise tolerance",              OFFSET(noise_str), AV_OPT_TYPE_STRING, {.str="-60dB"}, CHAR_MIN, CHAR_MAX },
+    { "d",         "set minimum duration in seconds",  OFFSET(duration),  AV_OPT_TYPE_INT,    {.dbl=2},    0, INT_MAX},
+    { "duration",  "set minimum duration in seconds",  OFFSET(duration),  AV_OPT_TYPE_INT,    {.dbl=2},    0, INT_MAX},
+    { NULL },
+};
+
+static const char *silencedetect_get_name(void *ctx)
+{
+    return "silencedetect";
+}
+
+static const AVClass silencedetect_class = {
+    .class_name = "SilenceDetectContext",
+    .item_name  = silencedetect_get_name,
+    .option     = silencedetect_options,
+};
+
+static av_cold int init(AVFilterContext *ctx, const char *args, void *opaque)
+{
+    int ret;
+    char *tail;
+    SilenceDetectContext *silence = ctx->priv;
+
+    silence->class = &silencedetect_class;
+    av_opt_set_defaults(silence);
+
+    if ((ret = av_set_options_string(silence, args, "=", ":")) < 0) {
+        av_log(ctx, AV_LOG_ERROR, "Error parsing options string: '%s'\n", args);
+        return ret;
+    }
+
+    silence->noise = strtod(silence->noise_str, &tail);
+    if (!strcmp(tail, "dB")) {
+        silence->noise = pow(10, silence->noise/20);
+    } else if (*tail) {
+        av_log(ctx, AV_LOG_ERROR, "Invalid value '%s' for noise parameter.\n",
+               silence->noise_str);
+        return AVERROR(EINVAL);
+    }
+
+    return 0;
+}
+
+static void filter_samples(AVFilterLink *inlink, AVFilterBufferRef *insamples)
+{
+    int i;
+    SilenceDetectContext *silence = inlink->dst->priv;
+    const int nb_channels           = av_get_channel_layout_nb_channels(inlink->channel_layout);
+    const int srate                 = inlink->sample_rate;
+    const int nb_samples            = insamples->audio->nb_samples * nb_channels;
+    const int64_t nb_samples_notify = srate * silence->duration    * nb_channels;
+
+    // scale number of null samples to the new sample rate
+    if (silence->last_sample_rate && silence->last_sample_rate != srate)
+        silence->nb_null_samples =
+            srate * silence->nb_null_samples / silence->last_sample_rate;
+    silence->last_sample_rate = srate;
+
+    // TODO: support more sample formats
+    if (insamples->format == AV_SAMPLE_FMT_DBL) {
+        double *p = (double *)insamples->data[0];
+
+        for (i = 0; i < nb_samples; i++, p++) {
+            if (*p < silence->noise && *p > -silence->noise) {
+                if (!silence->start) {
+                    silence->nb_null_samples++;
+                    if (silence->nb_null_samples >= nb_samples_notify) {
+                        silence->start = insamples->pts * av_q2d(inlink->time_base) - silence->duration;
+                        av_log(silence, AV_LOG_INFO,
+                               "silence_start: %f\n", silence->start);
+                    }
+                }
+            } else {
+                if (silence->start) {
+                    double end = insamples->pts * av_q2d(inlink->time_base);
+                    av_log(silence, AV_LOG_INFO,
+                           "silence_end: %f | silence_duration: %f\n",
+                           end, end - silence->start);
+                }
+                silence->nb_null_samples = silence->start = 0;
+            }
+        }
+    }
+
+    avfilter_filter_samples(inlink->dst->outputs[0], insamples);
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+    AVFilterFormats *formats = NULL;
+    enum AVSampleFormat sample_fmts[] = {
+        AV_SAMPLE_FMT_DBL,
+        AV_SAMPLE_FMT_NONE
+    };
+    int packing_fmts[] = { AVFILTER_PACKED, -1 };
+
+    formats = avfilter_make_all_channel_layouts();
+    if (!formats)
+        return AVERROR(ENOMEM);
+    avfilter_set_common_channel_layouts(ctx, formats);
+
+    formats = avfilter_make_format_list(sample_fmts);
+    if (!formats)
+        return AVERROR(ENOMEM);
+    avfilter_set_common_sample_formats(ctx, formats);
+
+    formats = avfilter_make_format_list(packing_fmts);
+    if (!formats)
+        return AVERROR(ENOMEM);
+    avfilter_set_common_packing_formats(ctx, formats);
+
+    return 0;
+}
+
+AVFilter avfilter_af_silencedetect = {
+    .name          = "silencedetect",
+    .description   = NULL_IF_CONFIG_SMALL("Detect silence."),
+    .priv_size     = sizeof(SilenceDetectContext),
+    .init          = init,
+    .query_formats = query_formats,
+
+    .inputs = (const AVFilterPad[]) {
+        { .name             = "default",
+          .type             = AVMEDIA_TYPE_AUDIO,
+          .get_audio_buffer = avfilter_null_get_audio_buffer,
+          .filter_samples   = filter_samples, },
+        { .name = NULL }
+    },
+    .outputs = (const AVFilterPad[]) {
+        { .name = "default",
+          .type = AVMEDIA_TYPE_AUDIO, },
+        { .name = NULL }
+    },
+};
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 621568e..a863a93 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -45,6 +45,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER (EARWAX,      earwax,      af);
     REGISTER_FILTER (PAN,         pan,         af);
     REGISTER_FILTER (VOLUME,      volume,      af);
+    REGISTER_FILTER (SILENCEDETECT, silencedetect, af);
 
     REGISTER_FILTER (ABUFFER,     abuffer,     asrc);
     REGISTER_FILTER (AEVALSRC,    aevalsrc,    asrc);
diff --git a/libavfilter/avfilter.h b/libavfilter/avfilter.h
index d88d3ab..9c79597 100644
--- a/libavfilter/avfilter.h
+++ b/libavfilter/avfilter.h
@@ -30,8 +30,8 @@
 #include "libavcodec/avcodec.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  2
-#define LIBAVFILTER_VERSION_MINOR 57
-#define LIBAVFILTER_VERSION_MICRO 101
+#define LIBAVFILTER_VERSION_MINOR 58
+#define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \
-- 
1.7.8.1

-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 490 bytes
Desc: not available
URL: <http://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20120107/8fcd4362/attachment.asc>


More information about the ffmpeg-devel mailing list