/*
  * 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 "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 of silence until notification
     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 }
     },
 };