/*
  * Copyright (c) 2012 Clément Bœsch <ubitux@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 <float.h> /* DBL_MAX */
 

 #include "libavutil/channel_layout.h"

 #include "libavutil/opt.h"

 #include "libavutil/timestamp.h"

 #include "audio.h"

 #include "formats.h"

 #include "avfilter.h"

 #include "internal.h"

 
 typedef struct {
     const AVClass *class;
     double noise;               ///< noise amplitude ratio

     double duration;            ///< minimum duration of silence until notification

     int64_t nb_null_samples;    ///< current number of continuous zero samples

     int64_t 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)

 #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_AUDIO_PARAM

 static const AVOption silencedetect_options[] = {

     { "n",         "set noise tolerance",              OFFSET(noise),     AV_OPT_TYPE_DOUBLE, {.dbl=0.001},          0, DBL_MAX,  FLAGS },
     { "noise",     "set noise tolerance",              OFFSET(noise),     AV_OPT_TYPE_DOUBLE, {.dbl=0.001},          0, DBL_MAX,  FLAGS },

     { "d",         "set minimum duration in seconds",  OFFSET(duration),  AV_OPT_TYPE_DOUBLE, {.dbl=2.},             0, 24*60*60, FLAGS },
     { "duration",  "set minimum duration in seconds",  OFFSET(duration),  AV_OPT_TYPE_DOUBLE, {.dbl=2.},             0, 24*60*60, FLAGS },

     { NULL },
 };
 

 AVFILTER_DEFINE_CLASS(silencedetect);

 static av_cold int init(AVFilterContext *ctx, const char *args)

 {
     int ret;
     SilenceDetectContext *silence = ctx->priv;
 
     silence->class = &silencedetect_class;
     av_opt_set_defaults(silence);
 

     if ((ret = av_set_options_string(silence, args, "=", ":")) < 0)

         return ret;
 

     av_opt_free(silence);

 
     return 0;
 }
 

 static char *get_metadata_val(AVFilterBufferRef *insamples, const char *key)
 {
     AVDictionaryEntry *e = av_dict_get(insamples->metadata, key, NULL, 0);
     return e && e->value ? e->value : NULL;
 }
 

 static int filter_frame(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

     // TODO: document metadata

     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 - (int64_t)(silence->duration / av_q2d(inlink->time_base) + .5);

                         av_dict_set(&insamples->metadata, "lavfi.silence_start",
                                     av_ts2timestr(silence->start, &inlink->time_base), 0);
                         av_log(silence, AV_LOG_INFO, "silence_start: %s\n",
                                get_metadata_val(insamples, "lavfi.silence_start"));

                     }
                 }
             } else {

                 if (silence->start) {
                     av_dict_set(&insamples->metadata, "lavfi.silence_end",
                                 av_ts2timestr(insamples->pts, &inlink->time_base), 0);
                     av_dict_set(&insamples->metadata, "lavfi.silence_duration",
                                 av_ts2timestr(insamples->pts - silence->start, &inlink->time_base), 0);

                     av_log(silence, AV_LOG_INFO,

                            "silence_end: %s | silence_duration: %s\n",

                            get_metadata_val(insamples, "lavfi.silence_end"),
                            get_metadata_val(insamples, "lavfi.silence_duration"));
                 }

                 silence->nb_null_samples = silence->start = 0;
             }
         }
     }
 

     return ff_filter_frame(inlink->dst->outputs[0], insamples);

 }
 
 static int query_formats(AVFilterContext *ctx)
 {
     AVFilterFormats *formats = NULL;

     AVFilterChannelLayouts *layouts = NULL;

     static const enum AVSampleFormat sample_fmts[] = {

         AV_SAMPLE_FMT_DBL,
         AV_SAMPLE_FMT_NONE
     };
 

     layouts = ff_all_channel_layouts();
     if (!layouts)

         return AVERROR(ENOMEM);

     ff_set_common_channel_layouts(ctx, layouts);

     formats = ff_make_format_list(sample_fmts);

     if (!formats)
         return AVERROR(ENOMEM);

     ff_set_common_formats(ctx, formats);

     formats = ff_all_samplerates();
     if (!formats)
         return AVERROR(ENOMEM);
     ff_set_common_samplerates(ctx, formats);
 

     return 0;
 }
 

 static const AVFilterPad silencedetect_inputs[] = {
     {
         .name             = "default",
         .type             = AVMEDIA_TYPE_AUDIO,
         .get_audio_buffer = ff_null_get_audio_buffer,
         .filter_frame     = filter_frame,
     },
     { NULL }
 };
 
 static const AVFilterPad silencedetect_outputs[] = {
     {
         .name = "default",
         .type = AVMEDIA_TYPE_AUDIO,
     },
     { NULL }
 };
 

 AVFilter avfilter_af_silencedetect = {
     .name          = "silencedetect",
     .description   = NULL_IF_CONFIG_SMALL("Detect silence."),
     .priv_size     = sizeof(SilenceDetectContext),
     .init          = init,
     .query_formats = query_formats,

     .inputs        = silencedetect_inputs,
     .outputs       = silencedetect_outputs,
     .priv_class    = &silencedetect_class,

 };