/*

  * Copyright (c) 2012 Clément Bœsch <u pkh me>

  *
  * 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/opt.h"

 #include "libavutil/timestamp.h"

 #include "audio.h"

 #include "formats.h"

 #include "avfilter.h"

 #include "internal.h"

 typedef struct SilenceDetectContext {

     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

 
     void (*silencedetect)(struct SilenceDetectContext *s, AVFrame *insamples,
                           int nb_samples, int64_t nb_samples_notify,
                           AVRational time_base);

 } 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 char *get_metadata_val(AVFrame *insamples, const char *key)

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

 static av_always_inline void update(SilenceDetectContext *s, AVFrame *insamples,
                                     int is_silence, int64_t nb_samples_notify,
                                     AVRational time_base)
 {
     if (is_silence) {
         if (!s->start) {
             s->nb_null_samples++;
             if (s->nb_null_samples >= nb_samples_notify) {
                 s->start = insamples->pts - (int64_t)(s->duration / av_q2d(time_base) + .5);
                 av_dict_set(&insamples->metadata, "lavfi.silence_start",
                             av_ts2timestr(s->start, &time_base), 0);
                 av_log(s, AV_LOG_INFO, "silence_start: %s\n",
                        get_metadata_val(insamples, "lavfi.silence_start"));
             }
         }
     } else {
         if (s->start) {
             av_dict_set(&insamples->metadata, "lavfi.silence_end",
                         av_ts2timestr(insamples->pts, &time_base), 0);
             av_dict_set(&insamples->metadata, "lavfi.silence_duration",
                         av_ts2timestr(insamples->pts - s->start, &time_base), 0);
             av_log(s, AV_LOG_INFO,
                    "silence_end: %s | silence_duration: %s\n",
                    get_metadata_val(insamples, "lavfi.silence_end"),
                    get_metadata_val(insamples, "lavfi.silence_duration"));
         }
         s->nb_null_samples = s->start = 0;
     }
 }
 
 #define SILENCE_DETECT(name, type)                                               \
 static void silencedetect_##name(SilenceDetectContext *s, AVFrame *insamples,    \
                                  int nb_samples, int64_t nb_samples_notify,      \
                                  AVRational time_base)                           \
 {                                                                                \
     const type *p = (const type *)insamples->data[0];                            \
     const type noise = s->noise;                                                 \
     int i;                                                                       \
                                                                                  \
     for (i = 0; i < nb_samples; i++, p++)                                        \
         update(s, insamples, *p < noise && *p > -noise,                          \
                nb_samples_notify, time_base);                                    \
 }
 
 SILENCE_DETECT(dbl, double)
 SILENCE_DETECT(flt, float)
 SILENCE_DETECT(s32, int32_t)
 SILENCE_DETECT(s16, int16_t)
 
 static int config_input(AVFilterLink *inlink)
 {
     AVFilterContext *ctx = inlink->dst;
     SilenceDetectContext *s = ctx->priv;
 
     switch (inlink->format) {
     case AV_SAMPLE_FMT_DBL: s->silencedetect = silencedetect_dbl; break;
     case AV_SAMPLE_FMT_FLT: s->silencedetect = silencedetect_flt; break;
     case AV_SAMPLE_FMT_S32:
         s->noise *= INT32_MAX;
         s->silencedetect = silencedetect_s32;
         break;
     case AV_SAMPLE_FMT_S16:
         s->noise *= INT16_MAX;
         s->silencedetect = silencedetect_s16;
         break;
     }
 
     return 0;
 }
 

 static int filter_frame(AVFilterLink *inlink, AVFrame *insamples)

 {

     SilenceDetectContext *s         = inlink->dst->priv;

     const int nb_channels           = inlink->channels;

     const int srate                 = inlink->sample_rate;

     const int nb_samples            = insamples->nb_samples     * nb_channels;

     const int64_t nb_samples_notify = srate * s->duration * nb_channels;

 
     // scale number of null samples to the new sample rate

     if (s->last_sample_rate && s->last_sample_rate != srate)
         s->nb_null_samples = srate * s->nb_null_samples / s->last_sample_rate;
     s->last_sample_rate = srate;

     // TODO: document metadata

     s->silencedetect(s, insamples, nb_samples, nb_samples_notify,
                      inlink->time_base);

     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_FLT,
         AV_SAMPLE_FMT_S32,
         AV_SAMPLE_FMT_S16,

         AV_SAMPLE_FMT_NONE
     };

     int ret;

     layouts = ff_all_channel_layouts();
     if (!layouts)

         return AVERROR(ENOMEM);

     ret = ff_set_common_channel_layouts(ctx, layouts);
     if (ret < 0)
         return ret;

     formats = ff_make_format_list(sample_fmts);

     if (!formats)
         return AVERROR(ENOMEM);

     ret = ff_set_common_formats(ctx, formats);
     if (ret < 0)
         return ret;

     formats = ff_all_samplerates();
     if (!formats)
         return AVERROR(ENOMEM);

     return ff_set_common_samplerates(ctx, formats);

 }
 

 static const AVFilterPad silencedetect_inputs[] = {
     {

         .name         = "default",
         .type         = AVMEDIA_TYPE_AUDIO,

         .config_props = config_input,

         .filter_frame = filter_frame,

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

 AVFilter ff_af_silencedetect = {

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

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

 };