/*

  * Copyright 2010 S.N. Hemanth Meenakshisundaram <smeenaks ucsd edu>
  * Copyright 2010 Stefano Sabatini <stefano.sabatini-lala poste it>
  *

  * 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
  * null audio source
  */
 

 #include <inttypes.h>
 #include <stdio.h>

 #include "libavutil/channel_layout.h"
 #include "libavutil/internal.h"

 #include "libavutil/opt.h"

 #include "audio.h"

 #include "avfilter.h"
 #include "internal.h"

 
 typedef struct {

     const AVClass *class;
     char   *channel_layout_str;

     uint64_t channel_layout;

     char   *sample_rate_str;
     int     sample_rate;

     int nb_samples;             ///< number of samples per requested frame
     int64_t pts;

 } ANullContext;
 

 #define OFFSET(x) offsetof(ANullContext, x)

 #define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM

 
 static const AVOption anullsrc_options[]= {

     { "channel_layout", "set channel_layout", OFFSET(channel_layout_str), AV_OPT_TYPE_STRING, {.str = "stereo"}, 0, 0, FLAGS },
     { "cl",             "set channel_layout", OFFSET(channel_layout_str), AV_OPT_TYPE_STRING, {.str = "stereo"}, 0, 0, FLAGS },
     { "sample_rate",    "set sample rate",    OFFSET(sample_rate_str)   , AV_OPT_TYPE_STRING, {.str = "44100"}, 0, 0, FLAGS },
     { "r",              "set sample rate",    OFFSET(sample_rate_str)   , AV_OPT_TYPE_STRING, {.str = "44100"}, 0, 0, FLAGS },

     { "nb_samples",     "set the number of samples per requested frame", OFFSET(nb_samples), AV_OPT_TYPE_INT, {.i64 = 1024}, 0, INT_MAX, FLAGS },
     { "n",              "set the number of samples per requested frame", OFFSET(nb_samples), AV_OPT_TYPE_INT, {.i64 = 1024}, 0, INT_MAX, FLAGS },

     { NULL },
 };
 

 AVFILTER_DEFINE_CLASS(anullsrc);

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

 {

     ANullContext *null = ctx->priv;

     int ret;

     null->class = &anullsrc_class;
     av_opt_set_defaults(null);

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

         return ret;

     if ((ret = ff_parse_sample_rate(&null->sample_rate,
                                      null->sample_rate_str, ctx)) < 0)

         return ret;
 

     if ((ret = ff_parse_channel_layout(&null->channel_layout,
                                         null->channel_layout_str, ctx)) < 0)

         return ret;

 
     return 0;
 }
 
 static int config_props(AVFilterLink *outlink)
 {

     ANullContext *null = outlink->src->priv;

     char buf[128];
     int chans_nb;
 

     outlink->sample_rate = null->sample_rate;
     outlink->channel_layout = null->channel_layout;

     chans_nb = av_get_channel_layout_nb_channels(null->channel_layout);
     av_get_channel_layout_string(buf, sizeof(buf), chans_nb, null->channel_layout);

     av_log(outlink->src, AV_LOG_VERBOSE,

            "sample_rate:%d channel_layout:'%s' nb_samples:%d\n",

            null->sample_rate, buf, null->nb_samples);

 
     return 0;
 }
 

 static int request_frame(AVFilterLink *outlink)

 {

     ANullContext *null = outlink->src->priv;
     AVFilterBufferRef *samplesref;
 
     samplesref =

         ff_get_audio_buffer(outlink, AV_PERM_WRITE, null->nb_samples);

     samplesref->pts = null->pts;
     samplesref->pos = -1;
     samplesref->audio->channel_layout = null->channel_layout;
     samplesref->audio->sample_rate = outlink->sample_rate;
 

     ff_filter_frame(outlink, avfilter_ref_buffer(samplesref, ~0));

     avfilter_unref_buffer(samplesref);
 
     null->pts += null->nb_samples;
     return 0;

 }
 

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

 AVFilter avfilter_asrc_anullsrc = {
     .name        = "anullsrc",

     .description = NULL_IF_CONFIG_SMALL("Null audio source, return empty audio frames."),

 
     .init        = init,
     .priv_size   = sizeof(ANullContext),
 

     .inputs      = NULL,

     .outputs     = avfilter_asrc_anullsrc_outputs,

     .priv_class = &anullsrc_class,

 };