/*
  * 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 "avfilter.h"

 #include "libavutil/audioconvert.h"

 
 typedef struct {
     int64_t channel_layout;
     int64_t sample_rate;
 } ANullContext;
 
 static int init(AVFilterContext *ctx, const char *args, void *opaque)
 {
     ANullContext *priv = ctx->priv;
     char channel_layout_str[128] = "";
 
     priv->sample_rate = 44100;

     priv->channel_layout = AV_CH_LAYOUT_STEREO;

 
     if (args)
         sscanf(args, "%"PRId64":%s", &priv->sample_rate, channel_layout_str);
 
     if (priv->sample_rate < 0) {
         av_log(ctx, AV_LOG_ERROR, "Invalid negative sample rate: %"PRId64"\n", priv->sample_rate);
         return AVERROR(EINVAL);
     }
 
     if (*channel_layout_str)

         if (!(priv->channel_layout = av_get_channel_layout(channel_layout_str))

             && sscanf(channel_layout_str, "%"PRId64, &priv->channel_layout) != 1) {
             av_log(ctx, AV_LOG_ERROR, "Invalid value '%s' for channel layout\n",
                    channel_layout_str);
             return AVERROR(EINVAL);
         }
 
     return 0;
 }
 
 static int config_props(AVFilterLink *outlink)
 {
     ANullContext *priv = outlink->src->priv;
     char buf[128];
     int chans_nb;
 
     outlink->sample_rate = priv->sample_rate;
     outlink->channel_layout = priv->channel_layout;
 

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

     av_log(outlink->src, AV_LOG_INFO,
            "sample_rate:%"PRId64 " channel_layout:%"PRId64 " channel_layout_description:'%s'\n",
            priv->sample_rate, priv->channel_layout, buf);
 
     return 0;
 }
 
 static int request_frame(AVFilterLink *link)
 {
     return -1;
 }
 
 AVFilter avfilter_asrc_anullsrc = {
     .name        = "anullsrc",
     .description = NULL_IF_CONFIG_SMALL("Null audio source, never return audio frames."),
 
     .init        = init,
     .priv_size   = sizeof(ANullContext),
 
     .inputs      = (AVFilterPad[]) {{ .name = NULL}},
 
     .outputs     = (AVFilterPad[]) {{ .name = "default",
                                       .type = AVMEDIA_TYPE_AUDIO,
                                       .config_props = config_props,
                                       .request_frame = request_frame, },
                                     { .name = NULL}},
 };