2 * This file is part of FFmpeg.
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.
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.
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
25 #include "libavutil/audioconvert.h"
28 int64_t channel_layout;
32 static int init(AVFilterContext *ctx, const char *args, void *opaque)
34 ANullContext *priv = ctx->priv;
35 char channel_layout_str[128] = "";
37 priv->sample_rate = 44100;
38 priv->channel_layout = AV_CH_LAYOUT_STEREO;
41 sscanf(args, "%"PRId64":%s", &priv->sample_rate, channel_layout_str);
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);
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",
53 return AVERROR(EINVAL);
59 static int config_props(AVFilterLink *outlink)
61 ANullContext *priv = outlink->src->priv;
65 outlink->sample_rate = priv->sample_rate;
66 outlink->channel_layout = priv->channel_layout;
68 chans_nb = av_get_channel_layout_nb_channels(priv->channel_layout);
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);
77 static int request_frame(AVFilterLink *link)
82 AVFilter avfilter_asrc_anullsrc = {
84 .description = NULL_IF_CONFIG_SMALL("Null audio source, never return audio frames."),
87 .priv_size = sizeof(ANullContext),
89 .inputs = (AVFilterPad[]) {{ .name = NULL}},
91 .outputs = (AVFilterPad[]) {{ .name = "default",
92 .type = AVMEDIA_TYPE_AUDIO,
93 .config_props = config_props,
94 .request_frame = request_frame, },