libavfilter/asrc_anullsrc.c

   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
  19 /**
  20  * @file
  21  * null audio source
  22  */
  23
  24 #include <inttypes.h>
  25 #include <stdio.h>
  26
  27 #include "libavutil/channel_layout.h"
  28 #include "libavutil/internal.h"
  29 #include "avfilter.h"
  30 #include "internal.h"
  31
  32 typedef struct {
  33     uint64_t channel_layout;
  34     int64_t sample_rate;
  35 } ANullContext;
  36
  37 static int init(AVFilterContext *ctx, const char *args)
  38 {
  39     ANullContext *priv = ctx->priv;
  40     char channel_layout_str[128] = "";
  41
  42     priv->sample_rate = 44100;
  43     priv->channel_layout = AV_CH_LAYOUT_STEREO;
  44
  45     if (args)
  46         sscanf(args, "%"PRId64":%s", &priv->sample_rate, channel_layout_str);
  47
  48     if (priv->sample_rate < 0) {
  49         av_log(ctx, AV_LOG_ERROR, "Invalid negative sample rate: %"PRId64"\n", priv->sample_rate);
  50         return AVERROR(EINVAL);
  51     }
  52
  53     if (*channel_layout_str)
  54         if (!(priv->channel_layout = av_get_channel_layout(channel_layout_str))
  55             && sscanf(channel_layout_str, "%"PRId64, &priv->channel_layout) != 1) {
  56             av_log(ctx, AV_LOG_ERROR, "Invalid value '%s' for channel layout\n",
  57                    channel_layout_str);
  58             return AVERROR(EINVAL);
  59         }
  60
  61     return 0;
  62 }
  63
  64 static int config_props(AVFilterLink *outlink)
  65 {
  66     ANullContext *priv = outlink->src->priv;
  67     char buf[128];
  68     int chans_nb;
  69
  70     outlink->sample_rate = priv->sample_rate;
  71     outlink->channel_layout = priv->channel_layout;
  72
  73     chans_nb = av_get_channel_layout_nb_channels(priv->channel_layout);
  74     av_get_channel_layout_string(buf, sizeof(buf), chans_nb, priv->channel_layout);
  75     av_log(outlink->src, AV_LOG_VERBOSE,
  76            "sample_rate:%"PRId64 " channel_layout:%"PRId64 " channel_layout_description:'%s'\n",
  77            priv->sample_rate, priv->channel_layout, buf);
  78
  79     return 0;
  80 }
  81
  82 static int request_frame(AVFilterLink *link)
  83 {
  84     return -1;
  85 }
  86
  87 static const AVFilterPad avfilter_asrc_anullsrc_outputs[] = {
  88     {
  89         .name          = "default",
  90         .type          = AVMEDIA_TYPE_AUDIO,
  91         .config_props  = config_props,
  92         .request_frame = request_frame,
  93     },
  94     { NULL }
  95 };
  96
  97 AVFilter avfilter_asrc_anullsrc = {
  98     .name        = "anullsrc",
  99     .description = NULL_IF_CONFIG_SMALL("Null audio source, never return audio frames."),
 100
 101     .init        = init,
 102     .priv_size   = sizeof(ANullContext),
 103
 104     .inputs      = NULL,
 105
 106     .outputs     = avfilter_asrc_anullsrc_outputs,
 107 };