| /* |
| * This file is part of FFmpeg. |
| * |
| * FFmpeg is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU Lesser General Public |
| * License as published by the Free Software Foundation; either |
| * version 2.1 of the License, or (at your option) any later version. |
| * |
| * FFmpeg is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| * Lesser General Public License for more details. |
| * |
| * You should have received a copy of the GNU Lesser General Public |
| * License along with FFmpeg; if not, write to the Free Software |
| * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| */ |
| |
| /** |
| * @file |
| * null audio source |
| */ |
| |
| #include "libavutil/audioconvert.h" |
| #include "libavutil/opt.h" |
| |
| #include "avfilter.h" |
| #include "internal.h" |
| |
| typedef struct { |
| const AVClass *class; |
| char *channel_layout_str; |
| uint64_t channel_layout; |
| char *sample_rate_str; |
| int sample_rate; |
| int nb_samples; ///< number of samples per requested frame |
| int64_t pts; |
| } ANullContext; |
| |
| #define OFFSET(x) offsetof(ANullContext, x) |
| |
| static const AVOption anullsrc_options[]= { |
| { "channel_layout", "set channel_layout", OFFSET(channel_layout_str), AV_OPT_TYPE_STRING, {.str = "stereo"}, 0, 0 }, |
| { "cl", "set channel_layout", OFFSET(channel_layout_str), AV_OPT_TYPE_STRING, {.str = "stereo"}, 0, 0 }, |
| { "sample_rate", "set sample rate", OFFSET(sample_rate_str) , AV_OPT_TYPE_STRING, {.str = "44100"}, 0, 0 }, |
| { "r", "set sample rate", OFFSET(sample_rate_str) , AV_OPT_TYPE_STRING, {.str = "44100"}, 0, 0 }, |
| { "nb_samples", "set the number of samples per requested frame", OFFSET(nb_samples), AV_OPT_TYPE_INT, {.dbl = 1024}, 0, INT_MAX }, |
| { "n", "set the number of samples per requested frame", OFFSET(nb_samples), AV_OPT_TYPE_INT, {.dbl = 1024}, 0, INT_MAX }, |
| { NULL }, |
| }; |
| |
| static const char *anullsrc_get_name(void *ctx) |
| { |
| return "anullsrc"; |
| } |
| |
| static const AVClass anullsrc_class = { |
| "ANullSrcContext", |
| anullsrc_get_name, |
| anullsrc_options |
| }; |
| |
| static int init(AVFilterContext *ctx, const char *args, void *opaque) |
| { |
| ANullContext *null = ctx->priv; |
| int ret; |
| |
| null->class = &anullsrc_class; |
| av_opt_set_defaults(null); |
| |
| if ((ret = (av_set_options_string(null, args, "=", ":"))) < 0) { |
| av_log(ctx, AV_LOG_ERROR, "Error parsing options string: '%s'\n", args); |
| return ret; |
| } |
| |
| if ((ret = ff_parse_sample_rate(&null->sample_rate, |
| null->sample_rate_str, ctx)) < 0) |
| return ret; |
| |
| if ((ret = ff_parse_channel_layout(&null->channel_layout, |
| null->channel_layout_str, ctx)) < 0) |
| return ret; |
| |
| return 0; |
| } |
| |
| static int config_props(AVFilterLink *outlink) |
| { |
| ANullContext *null = outlink->src->priv; |
| char buf[128]; |
| int chans_nb; |
| |
| outlink->sample_rate = null->sample_rate; |
| outlink->channel_layout = null->channel_layout; |
| |
| chans_nb = av_get_channel_layout_nb_channels(null->channel_layout); |
| av_get_channel_layout_string(buf, sizeof(buf), chans_nb, null->channel_layout); |
| av_log(outlink->src, AV_LOG_INFO, |
| "sample_rate:%d channel_layout:'%s' nb_samples:%d\n", |
| null->sample_rate, buf, null->nb_samples); |
| |
| return 0; |
| } |
| |
| static int request_frame(AVFilterLink *outlink) |
| { |
| ANullContext *null = outlink->src->priv; |
| AVFilterBufferRef *samplesref; |
| |
| samplesref = |
| avfilter_get_audio_buffer(outlink, AV_PERM_WRITE, null->nb_samples); |
| samplesref->pts = null->pts; |
| samplesref->pos = -1; |
| samplesref->audio->channel_layout = null->channel_layout; |
| samplesref->audio->sample_rate = outlink->sample_rate; |
| |
| avfilter_filter_samples(outlink, avfilter_ref_buffer(samplesref, ~0)); |
| avfilter_unref_buffer(samplesref); |
| |
| null->pts += null->nb_samples; |
| return 0; |
| } |
| |
| AVFilter avfilter_asrc_anullsrc = { |
| .name = "anullsrc", |
| .description = NULL_IF_CONFIG_SMALL("Null audio source, return empty audio frames."), |
| |
| .init = init, |
| .priv_size = sizeof(ANullContext), |
| |
| .inputs = (const AVFilterPad[]) {{ .name = NULL}}, |
| |
| .outputs = (const AVFilterPad[]) {{ .name = "default", |
| .type = AVMEDIA_TYPE_AUDIO, |
| .config_props = config_props, |
| .request_frame = request_frame, }, |
| { .name = NULL}}, |
| }; |