asrc_anullsrc.c
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1 /*
2  * This file is part of Libav.
3  *
4  * Libav is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU Lesser General Public
6  * License as published by the Free Software Foundation; either
7  * version 2.1 of the License, or (at your option) any later version.
8  *
9  * Libav is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12  * Lesser General Public License for more details.
13  *
14  * You should have received a copy of the GNU Lesser General Public
15  * License along with Libav; if not, write to the Free Software
16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17  */
18 
24 #include "avfilter.h"
25 #include "libavutil/audioconvert.h"
26 
27 typedef struct {
28  uint64_t channel_layout;
29  int64_t sample_rate;
30 } ANullContext;
31 
32 static int init(AVFilterContext *ctx, const char *args, void *opaque)
33 {
34  ANullContext *priv = ctx->priv;
35  char channel_layout_str[128] = "";
36 
37  priv->sample_rate = 44100;
39 
40  if (args)
41  sscanf(args, "%"PRId64":%s", &priv->sample_rate, channel_layout_str);
42 
43  if (priv->sample_rate < 0) {
44  av_log(ctx, AV_LOG_ERROR, "Invalid negative sample rate: %"PRId64"\n", priv->sample_rate);
45  return AVERROR(EINVAL);
46  }
47 
48  if (*channel_layout_str)
49  if (!(priv->channel_layout = av_get_channel_layout(channel_layout_str))
50  && sscanf(channel_layout_str, "%"PRId64, &priv->channel_layout) != 1) {
51  av_log(ctx, AV_LOG_ERROR, "Invalid value '%s' for channel layout\n",
52  channel_layout_str);
53  return AVERROR(EINVAL);
54  }
55 
56  return 0;
57 }
58 
59 static int config_props(AVFilterLink *outlink)
60 {
61  ANullContext *priv = outlink->src->priv;
62  char buf[128];
63  int chans_nb;
64 
65  outlink->sample_rate = priv->sample_rate;
66  outlink->channel_layout = priv->channel_layout;
67 
69  av_get_channel_layout_string(buf, sizeof(buf), chans_nb, priv->channel_layout);
70  av_log(outlink->src, AV_LOG_INFO,
71  "sample_rate:%"PRId64 " channel_layout:%"PRId64 " channel_layout_description:'%s'\n",
72  priv->sample_rate, priv->channel_layout, buf);
73 
74  return 0;
75 }
76 
77 static int request_frame(AVFilterLink *link)
78 {
79  return -1;
80 }
81 
83  .name = "anullsrc",
84  .description = NULL_IF_CONFIG_SMALL("Null audio source, never return audio frames."),
85 
86  .init = init,
87  .priv_size = sizeof(ANullContext),
88 
89  .inputs = (AVFilterPad[]) {{ .name = NULL}},
90 
91  .outputs = (AVFilterPad[]) {{ .name = "default",
92  .type = AVMEDIA_TYPE_AUDIO,
93  .config_props = config_props,
94  .request_frame = request_frame, },
95  { .name = NULL}},
96 };