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