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  1. /*
  2.  * Copyright 2010 S.N. Hemanth Meenakshisundaram <smeenaks ucsd edu>
  3.  * Copyright 2010 Stefano Sabatini <stefano.sabatini-lala poste it>
  4.  *
  5.  * This file is part of FFmpeg.
  6.  *
  7.  * FFmpeg is free software; you can redistribute it and/or
  8.  * modify it under the terms of the GNU Lesser General Public
  9.  * License as published by the Free Software Foundation; either
  10.  * version 2.1 of the License, or (at your option) any later version.
  11.  *
  12.  * FFmpeg is distributed in the hope that it will be useful,
  13.  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15.  * Lesser General Public License for more details.
  16.  *
  17.  * You should have received a copy of the GNU Lesser General Public
  18.  * License along with FFmpeg; if not, write to the Free Software
  19.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20.  */
  21.  
  22. /**
  23.  * @file
  24.  * null audio source
  25.  */
  26.  
  27. #include <inttypes.h>
  28. #include <stdio.h>
  29.  
  30. #include "libavutil/channel_layout.h"
  31. #include "libavutil/internal.h"
  32. #include "libavutil/opt.h"
  33. #include "audio.h"
  34. #include "avfilter.h"
  35. #include "internal.h"
  36.  
  37. typedef struct {
  38.     const AVClass *class;
  39.     char   *channel_layout_str;
  40.     uint64_t channel_layout;
  41.     char   *sample_rate_str;
  42.     int     sample_rate;
  43.     int nb_samples;             ///< number of samples per requested frame
  44.     int64_t pts;
  45. } ANullContext;
  46.  
  47. #define OFFSET(x) offsetof(ANullContext, x)
  48. #define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
  49.  
  50. static const AVOption anullsrc_options[]= {
  51.     { "channel_layout", "set channel_layout", OFFSET(channel_layout_str), AV_OPT_TYPE_STRING, {.str = "stereo"}, 0, 0, FLAGS },
  52.     { "cl",             "set channel_layout", OFFSET(channel_layout_str), AV_OPT_TYPE_STRING, {.str = "stereo"}, 0, 0, FLAGS },
  53.     { "sample_rate",    "set sample rate",    OFFSET(sample_rate_str)   , AV_OPT_TYPE_STRING, {.str = "44100"}, 0, 0, FLAGS },
  54.     { "r",              "set sample rate",    OFFSET(sample_rate_str)   , AV_OPT_TYPE_STRING, {.str = "44100"}, 0, 0, FLAGS },
  55.     { "nb_samples",     "set the number of samples per requested frame", OFFSET(nb_samples), AV_OPT_TYPE_INT, {.i64 = 1024}, 0, INT_MAX, FLAGS },
  56.     { "n",              "set the number of samples per requested frame", OFFSET(nb_samples), AV_OPT_TYPE_INT, {.i64 = 1024}, 0, INT_MAX, FLAGS },
  57.     { NULL }
  58. };
  59.  
  60. AVFILTER_DEFINE_CLASS(anullsrc);
  61.  
  62. static av_cold int init(AVFilterContext *ctx)
  63. {
  64.     ANullContext *null = ctx->priv;
  65.     int ret;
  66.  
  67.     if ((ret = ff_parse_sample_rate(&null->sample_rate,
  68.                                      null->sample_rate_str, ctx)) < 0)
  69.         return ret;
  70.  
  71.     if ((ret = ff_parse_channel_layout(&null->channel_layout,
  72.                                         null->channel_layout_str, ctx)) < 0)
  73.         return ret;
  74.  
  75.     return 0;
  76. }
  77.  
  78. static int query_formats(AVFilterContext *ctx)
  79. {
  80.     ANullContext *null = ctx->priv;
  81.     int64_t chlayouts[] = { null->channel_layout, -1 };
  82.     int sample_rates[] = { null->sample_rate, -1 };
  83.  
  84.     ff_set_common_formats        (ctx, ff_all_formats(AVMEDIA_TYPE_AUDIO));
  85.     ff_set_common_channel_layouts(ctx, avfilter_make_format64_list(chlayouts));
  86.     ff_set_common_samplerates    (ctx, ff_make_format_list(sample_rates));
  87.  
  88.     return 0;
  89. }
  90.  
  91. static int config_props(AVFilterLink *outlink)
  92. {
  93.     ANullContext *null = outlink->src->priv;
  94.     char buf[128];
  95.  
  96.     av_get_channel_layout_string(buf, sizeof(buf), 0, null->channel_layout);
  97.     av_log(outlink->src, AV_LOG_VERBOSE,
  98.            "sample_rate:%d channel_layout:'%s' nb_samples:%d\n",
  99.            null->sample_rate, buf, null->nb_samples);
  100.  
  101.     return 0;
  102. }
  103.  
  104. static int request_frame(AVFilterLink *outlink)
  105. {
  106.     int ret;
  107.     ANullContext *null = outlink->src->priv;
  108.     AVFrame *samplesref;
  109.  
  110.     samplesref = ff_get_audio_buffer(outlink, null->nb_samples);
  111.     if (!samplesref)
  112.         return AVERROR(ENOMEM);
  113.  
  114.     samplesref->pts = null->pts;
  115.     samplesref->channel_layout = null->channel_layout;
  116.     samplesref->sample_rate = outlink->sample_rate;
  117.  
  118.     ret = ff_filter_frame(outlink, av_frame_clone(samplesref));
  119.     av_frame_free(&samplesref);
  120.     if (ret < 0)
  121.         return ret;
  122.  
  123.     null->pts += null->nb_samples;
  124.     return ret;
  125. }
  126.  
  127. static const AVFilterPad avfilter_asrc_anullsrc_outputs[] = {
  128.     {
  129.         .name          = "default",
  130.         .type          = AVMEDIA_TYPE_AUDIO,
  131.         .config_props  = config_props,
  132.         .request_frame = request_frame,
  133.     },
  134.     { NULL }
  135. };
  136.  
  137. AVFilter avfilter_asrc_anullsrc = {
  138.     .name          = "anullsrc",
  139.     .description   = NULL_IF_CONFIG_SMALL("Null audio source, return empty audio frames."),
  140.     .init          = init,
  141.     .query_formats = query_formats,
  142.     .priv_size     = sizeof(ANullContext),
  143.     .inputs        = NULL,
  144.     .outputs       = avfilter_asrc_anullsrc_outputs,
  145.     .priv_class    = &anullsrc_class,
  146. };
  147.