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af_channelsplit.c
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1 /*
2  * This file is part of FFmpeg.
3  *
4  * FFmpeg 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  * FFmpeg 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 FFmpeg; if not, write to the Free Software
16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17  */
18 
19 /**
20  * @file
21  * Channel split filter
22  *
23  * Split an audio stream into per-channel streams.
24  */
25 
26 #include "libavutil/attributes.h"
28 #include "libavutil/internal.h"
29 #include "libavutil/opt.h"
30 
31 #include "audio.h"
32 #include "avfilter.h"
33 #include "formats.h"
34 #include "internal.h"
35 
36 typedef struct ChannelSplitContext {
37  const AVClass *class;
38 
39  uint64_t channel_layout;
42 
43 #define OFFSET(x) offsetof(ChannelSplitContext, x)
44 #define A AV_OPT_FLAG_AUDIO_PARAM
45 #define F AV_OPT_FLAG_FILTERING_PARAM
46 static const AVOption channelsplit_options[] = {
47  { "channel_layout", "Input channel layout.", OFFSET(channel_layout_str), AV_OPT_TYPE_STRING, { .str = "stereo" }, .flags = A|F },
48  { NULL }
49 };
50 
51 AVFILTER_DEFINE_CLASS(channelsplit);
52 
53 static av_cold int init(AVFilterContext *ctx)
54 {
55  ChannelSplitContext *s = ctx->priv;
56  int nb_channels;
57  int ret = 0, i;
58 
60  av_log(ctx, AV_LOG_ERROR, "Error parsing channel layout '%s'.\n",
62  ret = AVERROR(EINVAL);
63  goto fail;
64  }
65 
67  for (i = 0; i < nb_channels; i++) {
68  uint64_t channel = av_channel_layout_extract_channel(s->channel_layout, i);
69  AVFilterPad pad = { 0 };
70 
72  pad.name = av_get_channel_name(channel);
73 
74  ff_insert_outpad(ctx, i, &pad);
75  }
76 
77 fail:
78  return ret;
79 }
80 
82 {
83  ChannelSplitContext *s = ctx->priv;
84  AVFilterChannelLayouts *in_layouts = NULL;
85  int i;
86 
89 
90  ff_add_channel_layout(&in_layouts, s->channel_layout);
91  ff_channel_layouts_ref(in_layouts, &ctx->inputs[0]->out_channel_layouts);
92 
93  for (i = 0; i < ctx->nb_outputs; i++) {
94  AVFilterChannelLayouts *out_layouts = NULL;
95  uint64_t channel = av_channel_layout_extract_channel(s->channel_layout, i);
96 
97  ff_add_channel_layout(&out_layouts, channel);
98  ff_channel_layouts_ref(out_layouts, &ctx->outputs[i]->in_channel_layouts);
99  }
100 
101  return 0;
102 }
103 
104 static int filter_frame(AVFilterLink *inlink, AVFrame *buf)
105 {
106  AVFilterContext *ctx = inlink->dst;
107  int i, ret = 0;
108 
109  for (i = 0; i < ctx->nb_outputs; i++) {
110  AVFrame *buf_out = av_frame_clone(buf);
111 
112  if (!buf_out) {
113  ret = AVERROR(ENOMEM);
114  break;
115  }
116 
117  buf_out->data[0] = buf_out->extended_data[0] = buf_out->extended_data[i];
118  buf_out->channel_layout =
120  av_frame_set_channels(buf_out, 1);
121 
122  ret = ff_filter_frame(ctx->outputs[i], buf_out);
123  if (ret < 0)
124  break;
125  }
126  av_frame_free(&buf);
127  return ret;
128 }
129 
131  {
132  .name = "default",
133  .type = AVMEDIA_TYPE_AUDIO,
134  .filter_frame = filter_frame,
135  },
136  { NULL }
137 };
138 
140  .name = "channelsplit",
141  .description = NULL_IF_CONFIG_SMALL("Split audio into per-channel streams."),
142  .priv_size = sizeof(ChannelSplitContext),
143  .priv_class = &channelsplit_class,
144  .init = init,
146  .inputs = avfilter_af_channelsplit_inputs,
147  .outputs = NULL,
149 };