/*
  * Copyright (c) 2001 Heikki Leinonen
  * Copyright (c) 2001 Chris Bagwell
  * Copyright (c) 2003 Donnie Smith
  * Copyright (c) 2014 Paul B Mahol
  *
  * 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
  */
 
 #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"
 
 enum SilenceMode {
     SILENCE_TRIM,
     SILENCE_TRIM_FLUSH,
     SILENCE_COPY,
     SILENCE_COPY_FLUSH,
     SILENCE_STOP
 };
 
 typedef struct SilenceRemoveContext {
     const AVClass *class;
 
     enum SilenceMode mode;
 
     int start_periods;
     int64_t start_duration;
     double start_threshold;
 
     int stop_periods;
     int64_t stop_duration;
     double stop_threshold;
 
     double *start_holdoff;
     size_t start_holdoff_offset;
     size_t start_holdoff_end;
     int    start_found_periods;
 
     double *stop_holdoff;
     size_t stop_holdoff_offset;
     size_t stop_holdoff_end;
     int    stop_found_periods;
 

     double window_ratio;

     double *window;
     double *window_current;
     double *window_end;
     int window_size;

     double sum;

 
     int leave_silence;
     int restart;
     int64_t next_pts;

 
     int detection;
     void (*update)(struct SilenceRemoveContext *s, double sample);
     double(*compute)(struct SilenceRemoveContext *s, double sample);

 } SilenceRemoveContext;
 
 #define OFFSET(x) offsetof(SilenceRemoveContext, x)
 #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_AUDIO_PARAM
 static const AVOption silenceremove_options[] = {
     { "start_periods",   NULL, OFFSET(start_periods),   AV_OPT_TYPE_INT,      {.i64=0},     0,    9000, FLAGS },
     { "start_duration",  NULL, OFFSET(start_duration),  AV_OPT_TYPE_DURATION, {.i64=0},     0,    9000, FLAGS },
     { "start_threshold", NULL, OFFSET(start_threshold), AV_OPT_TYPE_DOUBLE,   {.dbl=0},     0, DBL_MAX, FLAGS },
     { "stop_periods",    NULL, OFFSET(stop_periods),    AV_OPT_TYPE_INT,      {.i64=0}, -9000,    9000, FLAGS },
     { "stop_duration",   NULL, OFFSET(stop_duration),   AV_OPT_TYPE_DURATION, {.i64=0},     0,    9000, FLAGS },
     { "stop_threshold",  NULL, OFFSET(stop_threshold),  AV_OPT_TYPE_DOUBLE,   {.dbl=0},     0, DBL_MAX, FLAGS },

     { "leave_silence",   NULL, OFFSET(leave_silence),   AV_OPT_TYPE_BOOL,     {.i64=0},     0,       1, FLAGS },

     { "detection",       NULL, OFFSET(detection),       AV_OPT_TYPE_INT,      {.i64=1},     0,       1, FLAGS, "detection" },
     {   "peak",          0,    0,                       AV_OPT_TYPE_CONST,    {.i64=0},     0,       0, FLAGS, "detection" },
     {   "rms",           0,    0,                       AV_OPT_TYPE_CONST,    {.i64=1},     0,       0, FLAGS, "detection" },

     { "window",          NULL, OFFSET(window_ratio),    AV_OPT_TYPE_DOUBLE,   {.dbl=0.02},  0,      10, FLAGS },

     { NULL }
 };
 
 AVFILTER_DEFINE_CLASS(silenceremove);
 

 static double compute_peak(SilenceRemoveContext *s, double sample)
 {
     double new_sum;
 
     new_sum  = s->sum;
     new_sum -= *s->window_current;
     new_sum += fabs(sample);
 
     return new_sum / s->window_size;
 }
 
 static void update_peak(SilenceRemoveContext *s, double sample)
 {
     s->sum -= *s->window_current;
     *s->window_current = fabs(sample);
     s->sum += *s->window_current;
 
     s->window_current++;
     if (s->window_current >= s->window_end)
         s->window_current = s->window;
 }
 
 static double compute_rms(SilenceRemoveContext *s, double sample)
 {
     double new_sum;
 
     new_sum  = s->sum;
     new_sum -= *s->window_current;
     new_sum += sample * sample;
 
     return sqrt(new_sum / s->window_size);
 }
 
 static void update_rms(SilenceRemoveContext *s, double sample)
 {
     s->sum -= *s->window_current;
     *s->window_current = sample * sample;
     s->sum += *s->window_current;
 
     s->window_current++;
     if (s->window_current >= s->window_end)
         s->window_current = s->window;
 }
 

 static av_cold int init(AVFilterContext *ctx)
 {
     SilenceRemoveContext *s = ctx->priv;
 
     if (s->stop_periods < 0) {
         s->stop_periods = -s->stop_periods;
         s->restart = 1;
     }
 

     switch (s->detection) {
     case 0:
         s->update = update_peak;
         s->compute = compute_peak;
         break;
     case 1:
         s->update = update_rms;
         s->compute = compute_rms;
         break;
     };
 

     return 0;
 }
 

 static void clear_window(SilenceRemoveContext *s)

 {
     memset(s->window, 0, s->window_size * sizeof(*s->window));
 
     s->window_current = s->window;
     s->window_end = s->window + s->window_size;

     s->sum = 0;

 }
 
 static int config_input(AVFilterLink *inlink)
 {
     AVFilterContext *ctx = inlink->dst;
     SilenceRemoveContext *s = ctx->priv;
 

     s->window_size = FFMAX((inlink->sample_rate * s->window_ratio), 1) * inlink->channels;

     s->window = av_malloc_array(s->window_size, sizeof(*s->window));
     if (!s->window)
         return AVERROR(ENOMEM);
 

     clear_window(s);

 
     s->start_duration = av_rescale(s->start_duration, inlink->sample_rate,
                                    AV_TIME_BASE);

     if (s->start_duration < 0) {
         av_log(ctx, AV_LOG_WARNING, "start duration must be non-negative\n");
         s->start_duration = -s->start_duration;
     }
 

     s->stop_duration  = av_rescale(s->stop_duration, inlink->sample_rate,
                                    AV_TIME_BASE);

     if (s->stop_duration < 0) {
         av_log(ctx, AV_LOG_WARNING, "stop duration must be non-negative\n");
         s->stop_duration = -s->stop_duration;
     }

 
     s->start_holdoff = av_malloc_array(FFMAX(s->start_duration, 1),
                                        sizeof(*s->start_holdoff) *
                                        inlink->channels);
     if (!s->start_holdoff)
         return AVERROR(ENOMEM);
 
     s->start_holdoff_offset = 0;
     s->start_holdoff_end    = 0;
     s->start_found_periods  = 0;
 
     s->stop_holdoff = av_malloc_array(FFMAX(s->stop_duration, 1),
                                       sizeof(*s->stop_holdoff) *
                                       inlink->channels);
     if (!s->stop_holdoff)
         return AVERROR(ENOMEM);
 
     s->stop_holdoff_offset = 0;
     s->stop_holdoff_end    = 0;
     s->stop_found_periods  = 0;
 
     if (s->start_periods)
         s->mode = SILENCE_TRIM;
     else
         s->mode = SILENCE_COPY;
 
     return 0;
 }
 

 static void flush(SilenceRemoveContext *s,
                   AVFrame *out, AVFilterLink *outlink,

                   int *nb_samples_written, int *ret)
 {
     if (*nb_samples_written) {
         out->nb_samples = *nb_samples_written / outlink->channels;

 
         out->pts = s->next_pts;
         s->next_pts += av_rescale_q(out->nb_samples,
                                     (AVRational){1, outlink->sample_rate},
                                     outlink->time_base);
 

         *ret = ff_filter_frame(outlink, out);
         *nb_samples_written = 0;
     } else {
         av_frame_free(&out);
     }
 }
 
 static int filter_frame(AVFilterLink *inlink, AVFrame *in)
 {
     AVFilterContext *ctx = inlink->dst;
     AVFilterLink *outlink = ctx->outputs[0];
     SilenceRemoveContext *s = ctx->priv;
     int i, j, threshold, ret = 0;
     int nbs, nb_samples_read, nb_samples_written;
     double *obuf, *ibuf = (double *)in->data[0];
     AVFrame *out;
 
     nb_samples_read = nb_samples_written = 0;
 
     switch (s->mode) {
     case SILENCE_TRIM:
 silence_trim:
         nbs = in->nb_samples - nb_samples_read / inlink->channels;
         if (!nbs)
             break;
 
         for (i = 0; i < nbs; i++) {
             threshold = 0;
             for (j = 0; j < inlink->channels; j++) {

                 threshold |= s->compute(s, ibuf[j]) > s->start_threshold;

             }
 
             if (threshold) {
                 for (j = 0; j < inlink->channels; j++) {

                     s->update(s, *ibuf);

                     s->start_holdoff[s->start_holdoff_end++] = *ibuf++;
                 }

                 nb_samples_read += inlink->channels;

 
                 if (s->start_holdoff_end >= s->start_duration * inlink->channels) {
                     if (++s->start_found_periods >= s->start_periods) {
                         s->mode = SILENCE_TRIM_FLUSH;
                         goto silence_trim_flush;
                     }
 
                     s->start_holdoff_offset = 0;
                     s->start_holdoff_end = 0;
                 }
             } else {
                 s->start_holdoff_end = 0;
 
                 for (j = 0; j < inlink->channels; j++)

                     s->update(s, ibuf[j]);

 
                 ibuf += inlink->channels;
                 nb_samples_read += inlink->channels;
             }
         }
         break;
 
     case SILENCE_TRIM_FLUSH:
 silence_trim_flush:
         nbs  = s->start_holdoff_end - s->start_holdoff_offset;
         nbs -= nbs % inlink->channels;
         if (!nbs)
             break;
 
         out = ff_get_audio_buffer(inlink, nbs / inlink->channels);
         if (!out) {
             av_frame_free(&in);
             return AVERROR(ENOMEM);
         }
 
         memcpy(out->data[0], &s->start_holdoff[s->start_holdoff_offset],
                nbs * sizeof(double));

 
         out->pts = s->next_pts;
         s->next_pts += av_rescale_q(out->nb_samples,
                                     (AVRational){1, outlink->sample_rate},
                                     outlink->time_base);
 

         s->start_holdoff_offset += nbs;
 
         ret = ff_filter_frame(outlink, out);
 
         if (s->start_holdoff_offset == s->start_holdoff_end) {
             s->start_holdoff_offset = 0;
             s->start_holdoff_end = 0;
             s->mode = SILENCE_COPY;
             goto silence_copy;
         }
         break;
 
     case SILENCE_COPY:
 silence_copy:
         nbs = in->nb_samples - nb_samples_read / inlink->channels;
         if (!nbs)
             break;
 
         out = ff_get_audio_buffer(inlink, nbs);
         if (!out) {
             av_frame_free(&in);
             return AVERROR(ENOMEM);
         }
         obuf = (double *)out->data[0];
 
         if (s->stop_periods) {
             for (i = 0; i < nbs; i++) {
                 threshold = 1;
                 for (j = 0; j < inlink->channels; j++)

                     threshold &= s->compute(s, ibuf[j]) > s->stop_threshold;

 
                 if (threshold && s->stop_holdoff_end && !s->leave_silence) {
                     s->mode = SILENCE_COPY_FLUSH;

                     flush(s, out, outlink, &nb_samples_written, &ret);

                     goto silence_copy_flush;
                 } else if (threshold) {
                     for (j = 0; j < inlink->channels; j++) {

                         s->update(s, *ibuf);

                         *obuf++ = *ibuf++;
                     }

                     nb_samples_read    += inlink->channels;
                     nb_samples_written += inlink->channels;

                 } else if (!threshold) {
                     for (j = 0; j < inlink->channels; j++) {

                         s->update(s, *ibuf);

                         if (s->leave_silence) {
                             *obuf++ = *ibuf;
                             nb_samples_written++;
                         }
 
                         s->stop_holdoff[s->stop_holdoff_end++] = *ibuf++;
                     }

                     nb_samples_read += inlink->channels;

 
                     if (s->stop_holdoff_end >= s->stop_duration * inlink->channels) {
                         if (++s->stop_found_periods >= s->stop_periods) {
                             s->stop_holdoff_offset = 0;
                             s->stop_holdoff_end = 0;
 
                             if (!s->restart) {
                                 s->mode = SILENCE_STOP;

                                 flush(s, out, outlink, &nb_samples_written, &ret);

                                 goto silence_stop;
                             } else {
                                 s->stop_found_periods = 0;
                                 s->start_found_periods = 0;
                                 s->start_holdoff_offset = 0;
                                 s->start_holdoff_end = 0;

                                 clear_window(s);

                                 s->mode = SILENCE_TRIM;

                                 flush(s, out, outlink, &nb_samples_written, &ret);

                                 goto silence_trim;
                             }
                         }

                         s->mode = SILENCE_COPY_FLUSH;

                         flush(s, out, outlink, &nb_samples_written, &ret);

                         goto silence_copy_flush;

                     }
                 }
             }

             flush(s, out, outlink, &nb_samples_written, &ret);

         } else {
             memcpy(obuf, ibuf, sizeof(double) * nbs * inlink->channels);

 
             out->pts = s->next_pts;
             s->next_pts += av_rescale_q(out->nb_samples,
                                         (AVRational){1, outlink->sample_rate},
                                         outlink->time_base);
 

             ret = ff_filter_frame(outlink, out);
         }
         break;
 
     case SILENCE_COPY_FLUSH:
 silence_copy_flush:
         nbs  = s->stop_holdoff_end - s->stop_holdoff_offset;
         nbs -= nbs % inlink->channels;
         if (!nbs)
             break;
 
         out = ff_get_audio_buffer(inlink, nbs / inlink->channels);
         if (!out) {
             av_frame_free(&in);
             return AVERROR(ENOMEM);
         }
 
         memcpy(out->data[0], &s->stop_holdoff[s->stop_holdoff_offset],
                nbs * sizeof(double));
         s->stop_holdoff_offset += nbs;
 

         out->pts = s->next_pts;
         s->next_pts += av_rescale_q(out->nb_samples,
                                     (AVRational){1, outlink->sample_rate},
                                     outlink->time_base);
 

         ret = ff_filter_frame(outlink, out);
 
         if (s->stop_holdoff_offset == s->stop_holdoff_end) {
             s->stop_holdoff_offset = 0;
             s->stop_holdoff_end = 0;
             s->mode = SILENCE_COPY;
             goto silence_copy;
         }
         break;
     case SILENCE_STOP:
 silence_stop:
         break;
     }
 
     av_frame_free(&in);
 
     return ret;
 }
 
 static int request_frame(AVFilterLink *outlink)
 {
     AVFilterContext *ctx = outlink->src;
     SilenceRemoveContext *s = ctx->priv;
     int ret;
 
     ret = ff_request_frame(ctx->inputs[0]);
     if (ret == AVERROR_EOF && (s->mode == SILENCE_COPY_FLUSH ||
                                s->mode == SILENCE_COPY)) {
         int nbs = s->stop_holdoff_end - s->stop_holdoff_offset;
         if (nbs) {
             AVFrame *frame;
 
             frame = ff_get_audio_buffer(outlink, nbs / outlink->channels);
             if (!frame)
                 return AVERROR(ENOMEM);
 
             memcpy(frame->data[0], &s->stop_holdoff[s->stop_holdoff_offset],
                    nbs * sizeof(double));

 
             frame->pts = s->next_pts;
             s->next_pts += av_rescale_q(frame->nb_samples,
                                         (AVRational){1, outlink->sample_rate},
                                         outlink->time_base);
 

             ret = ff_filter_frame(outlink, frame);

         }
         s->mode = SILENCE_STOP;
     }
     return ret;
 }
 
 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
     };

     int ret;

     layouts = ff_all_channel_counts();

     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 av_cold void uninit(AVFilterContext *ctx)
 {
     SilenceRemoveContext *s = ctx->priv;
 
     av_freep(&s->start_holdoff);
     av_freep(&s->stop_holdoff);
     av_freep(&s->window);
 }
 
 static const AVFilterPad silenceremove_inputs[] = {
     {
         .name         = "default",
         .type         = AVMEDIA_TYPE_AUDIO,
         .config_props = config_input,
         .filter_frame = filter_frame,
     },
     { NULL }
 };
 
 static const AVFilterPad silenceremove_outputs[] = {
     {
         .name          = "default",
         .type          = AVMEDIA_TYPE_AUDIO,
         .request_frame = request_frame,
     },
     { NULL }
 };
 
 AVFilter ff_af_silenceremove = {
     .name          = "silenceremove",
     .description   = NULL_IF_CONFIG_SMALL("Remove silence."),
     .priv_size     = sizeof(SilenceRemoveContext),
     .priv_class    = &silenceremove_class,
     .init          = init,
     .uninit        = uninit,
     .query_formats = query_formats,
     .inputs        = silenceremove_inputs,
     .outputs       = silenceremove_outputs,
 };