FFmpeg: libavfilter/asrc_anullsrc.c Source File

FFmpeg
asrc_anullsrc.c
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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, NULL,
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 ff_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 };
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