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
24 #include "libavutil/audioconvert.h"
25 #include "libavutil/opt.h"
32 char *channel_layout_str;
33 uint64_t channel_layout;
34 char *sample_rate_str;
36 int nb_samples; ///< number of samples per requested frame
40 #define OFFSET(x) offsetof(ANullContext, x)
42 static const AVOption anullsrc_options[]= {
43 { "channel_layout", "set channel_layout", OFFSET(channel_layout_str), AV_OPT_TYPE_STRING, {.str = "stereo"}, 0, 0 },
44 { "cl", "set channel_layout", OFFSET(channel_layout_str), AV_OPT_TYPE_STRING, {.str = "stereo"}, 0, 0 },
45 { "sample_rate", "set sample rate", OFFSET(sample_rate_str) , AV_OPT_TYPE_STRING, {.str = "44100"}, 0, 0 },
46 { "r", "set sample rate", OFFSET(sample_rate_str) , AV_OPT_TYPE_STRING, {.str = "44100"}, 0, 0 },
47 { "nb_samples", "set the number of samples per requested frame", OFFSET(nb_samples), AV_OPT_TYPE_INT, {.dbl = 1024}, 0, INT_MAX },
48 { "n", "set the number of samples per requested frame", OFFSET(nb_samples), AV_OPT_TYPE_INT, {.dbl = 1024}, 0, INT_MAX },
52 static const char *anullsrc_get_name(void *ctx)
57 static const AVClass anullsrc_class = {
63 static int init(AVFilterContext *ctx, const char *args, void *opaque)
65 ANullContext *null = ctx->priv;
68 null->class = &anullsrc_class;
69 av_opt_set_defaults(null);
71 if ((ret = (av_set_options_string(null, args, "=", ":"))) < 0) {
72 av_log(ctx, AV_LOG_ERROR, "Error parsing options string: '%s'\n", args);
76 if ((ret = ff_parse_sample_rate(&null->sample_rate,
77 null->sample_rate_str, ctx)) < 0)
80 if ((ret = ff_parse_channel_layout(&null->channel_layout,
81 null->channel_layout_str, ctx)) < 0)
87 static int config_props(AVFilterLink *outlink)
89 ANullContext *null = outlink->src->priv;
93 outlink->sample_rate = null->sample_rate;
94 outlink->channel_layout = null->channel_layout;
96 chans_nb = av_get_channel_layout_nb_channels(null->channel_layout);
97 av_get_channel_layout_string(buf, sizeof(buf), chans_nb, null->channel_layout);
98 av_log(outlink->src, AV_LOG_INFO,
99 "sample_rate:%d channel_layout:'%s' nb_samples:%d\n",
100 null->sample_rate, buf, null->nb_samples);
105 static int request_frame(AVFilterLink *outlink)
107 ANullContext *null = outlink->src->priv;
108 AVFilterBufferRef *samplesref;
111 avfilter_get_audio_buffer(outlink, AV_PERM_WRITE, null->nb_samples);
112 samplesref->pts = null->pts;
113 samplesref->pos = -1;
114 samplesref->audio->channel_layout = null->channel_layout;
115 samplesref->audio->sample_rate = outlink->sample_rate;
117 avfilter_filter_samples(outlink, avfilter_ref_buffer(samplesref, ~0));
118 avfilter_unref_buffer(samplesref);
120 null->pts += null->nb_samples;
124 AVFilter avfilter_asrc_anullsrc = {
126 .description = NULL_IF_CONFIG_SMALL("Null audio source, return empty audio frames."),
129 .priv_size = sizeof(ANullContext),
131 .inputs = (const AVFilterPad[]) {{ .name = NULL}},
133 .outputs = (const AVFilterPad[]) {{ .name = "default",
134 .type = AVMEDIA_TYPE_AUDIO,
135 .config_props = config_props,
136 .request_frame = request_frame, },