Libav
vsrc_nullsrc.c
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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 
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/opt.h"
31 #include "libavutil/parseutils.h"
32 #include "avfilter.h"
33 #include "formats.h"
34 #include "internal.h"
35 
36 static const char *const var_names[] = {
37  "E",
38  "PHI",
39  "PI",
40  "AVTB", /* default timebase 1/AV_TIME_BASE */
41  NULL
42 };
43 
44 enum var_name {
50 };
51 
52 typedef struct {
53  const AVClass *class;
54  int w, h;
55  char *tb_expr;
56  double var_values[VAR_VARS_NB];
57 } NullContext;
58 
59 static int config_props(AVFilterLink *outlink)
60 {
61  AVFilterContext *ctx = outlink->src;
62  NullContext *priv = ctx->priv;
63  AVRational tb;
64  int ret;
65  double res;
66 
67  priv->var_values[VAR_E] = M_E;
68  priv->var_values[VAR_PHI] = M_PHI;
69  priv->var_values[VAR_PI] = M_PI;
71 
72  if ((ret = av_expr_parse_and_eval(&res, priv->tb_expr, var_names, priv->var_values,
73  NULL, NULL, NULL, NULL, NULL, 0, NULL)) < 0) {
74  av_log(ctx, AV_LOG_ERROR, "Invalid expression '%s' for timebase.\n", priv->tb_expr);
75  return ret;
76  }
77  tb = av_d2q(res, INT_MAX);
78  if (tb.num <= 0 || tb.den <= 0) {
79  av_log(ctx, AV_LOG_ERROR,
80  "Invalid non-positive value for the timebase %d/%d.\n",
81  tb.num, tb.den);
82  return AVERROR(EINVAL);
83  }
84 
85  outlink->w = priv->w;
86  outlink->h = priv->h;
87  outlink->time_base = tb;
88 
89  av_log(outlink->src, AV_LOG_VERBOSE, "w:%d h:%d tb:%d/%d\n", priv->w, priv->h,
90  tb.num, tb.den);
91 
92  return 0;
93 }
94 
95 static int request_frame(AVFilterLink *link)
96 {
97  return -1;
98 }
99 
100 #define OFFSET(x) offsetof(NullContext, x)
101 #define FLAGS AV_OPT_FLAG_VIDEO_PARAM
102 static const AVOption options[] = {
103  { "width", NULL, OFFSET(w), AV_OPT_TYPE_INT, { .i64 = 352 }, 1, INT_MAX, FLAGS },
104  { "height", NULL, OFFSET(h), AV_OPT_TYPE_INT, { .i64 = 288 }, 1, INT_MAX, FLAGS },
105  { "timebase", NULL, OFFSET(tb_expr), AV_OPT_TYPE_STRING, { .str = "AVTB" }, 0, 0, FLAGS },
106  { NULL },
107 };
108 
109 static const AVClass nullsrc_class = {
110  .class_name = "nullsrc",
111  .item_name = av_default_item_name,
112  .option = options,
113  .version = LIBAVUTIL_VERSION_INT,
114 };
115 
117  {
118  .name = "default",
119  .type = AVMEDIA_TYPE_VIDEO,
120  .config_props = config_props,
121  .request_frame = request_frame,
122  },
123  { NULL }
124 };
125 
127  .name = "nullsrc",
128  .description = NULL_IF_CONFIG_SMALL("Null video source, never return images."),
129 
130  .priv_size = sizeof(NullContext),
131  .priv_class = &nullsrc_class,
132 
133  .inputs = NULL,
134 
135  .outputs = avfilter_vsrc_nullsrc_outputs,
136 };