libavfilter/vsrc_nullsrc.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 video source
  22  */
  23
  24 #include <stdio.h>
  25
  26 #include "libavutil/avstring.h"
  27 #include "libavutil/eval.h"
  28 #include "libavutil/internal.h"
  29 #include "libavutil/mathematics.h"
  30 #include "libavutil/parseutils.h"
  31 #include "avfilter.h"
  32 #include "formats.h"
  33 #include "internal.h"
  34
  35 static const char *const var_names[] = {
  36     "E",
  37     "PHI",
  38     "PI",
  39     "AVTB",   /* default timebase 1/AV_TIME_BASE */
  40     NULL
  41 };
  42
  43 enum var_name {
  44     VAR_E,
  45     VAR_PHI,
  46     VAR_PI,
  47     VAR_AVTB,
  48     VAR_VARS_NB
  49 };
  50
  51 typedef struct {
  52     int w, h;
  53     char tb_expr[256];
  54     double var_values[VAR_VARS_NB];
  55 } NullContext;
  56
  57 static int init(AVFilterContext *ctx, const char *args)
  58 {
  59     NullContext *priv = ctx->priv;
  60
  61     priv->w = 352;
  62     priv->h = 288;
  63     av_strlcpy(priv->tb_expr, "AVTB", sizeof(priv->tb_expr));
  64
  65     if (args)
  66         sscanf(args, "%d:%d:%255[^:]", &priv->w, &priv->h, priv->tb_expr);
  67
  68     if (priv->w <= 0 || priv->h <= 0) {
  69         av_log(ctx, AV_LOG_ERROR, "Non-positive size values are not acceptable.\n");
  70         return AVERROR(EINVAL);
  71     }
  72
  73     return 0;
  74 }
  75
  76 static int config_props(AVFilterLink *outlink)
  77 {
  78     AVFilterContext *ctx = outlink->src;
  79     NullContext *priv = ctx->priv;
  80     AVRational tb;
  81     int ret;
  82     double res;
  83
  84     priv->var_values[VAR_E]    = M_E;
  85     priv->var_values[VAR_PHI]  = M_PHI;
  86     priv->var_values[VAR_PI]   = M_PI;
  87     priv->var_values[VAR_AVTB] = av_q2d(AV_TIME_BASE_Q);
  88
  89     if ((ret = av_expr_parse_and_eval(&res, priv->tb_expr, var_names, priv->var_values,
  90                                       NULL, NULL, NULL, NULL, NULL, 0, NULL)) < 0) {
  91         av_log(ctx, AV_LOG_ERROR, "Invalid expression '%s' for timebase.\n", priv->tb_expr);
  92         return ret;
  93     }
  94     tb = av_d2q(res, INT_MAX);
  95     if (tb.num <= 0 || tb.den <= 0) {
  96         av_log(ctx, AV_LOG_ERROR,
  97                "Invalid non-positive value for the timebase %d/%d.\n",
  98                tb.num, tb.den);
  99         return AVERROR(EINVAL);
 100     }
 101
 102     outlink->w = priv->w;
 103     outlink->h = priv->h;
 104     outlink->time_base = tb;
 105
 106     av_log(outlink->src, AV_LOG_VERBOSE, "w:%d h:%d tb:%d/%d\n", priv->w, priv->h,
 107            tb.num, tb.den);
 108
 109     return 0;
 110 }
 111
 112 static int request_frame(AVFilterLink *link)
 113 {
 114     return -1;
 115 }
 116
 117 static const AVFilterPad avfilter_vsrc_nullsrc_outputs[] = {
 118     {
 119         .name          = "default",
 120         .type          = AVMEDIA_TYPE_VIDEO,
 121         .config_props  = config_props,
 122         .request_frame = request_frame,
 123     },
 124     { NULL }
 125 };
 126
 127 AVFilter avfilter_vsrc_nullsrc = {
 128     .name        = "nullsrc",
 129     .description = NULL_IF_CONFIG_SMALL("Null video source, never return images."),
 130
 131     .init       = init,
 132     .priv_size = sizeof(NullContext),
 133
 134     .inputs    = NULL,
 135
 136     .outputs   = avfilter_vsrc_nullsrc_outputs,
 137 };