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00024 #include "libavutil/avstring.h"
00025 #include "libavutil/eval.h"
00026 #include "libavutil/mathematics.h"
00027 #include "libavutil/parseutils.h"
00028 #include "avfilter.h"
00029
00030 static const char *var_names[] = {
00031 "E",
00032 "PHI",
00033 "PI",
00034 "AVTB",
00035 NULL
00036 };
00037
00038 enum var_name {
00039 VAR_E,
00040 VAR_PHI,
00041 VAR_PI,
00042 VAR_AVTB,
00043 VAR_VARS_NB
00044 };
00045
00046 typedef struct {
00047 int w, h;
00048 char tb_expr[256];
00049 double var_values[VAR_VARS_NB];
00050 } NullContext;
00051
00052 static int init(AVFilterContext *ctx, const char *args, void *opaque)
00053 {
00054 NullContext *priv = ctx->priv;
00055
00056 priv->w = 352;
00057 priv->h = 288;
00058 av_strlcpy(priv->tb_expr, "AVTB", sizeof(priv->tb_expr));
00059
00060 if (args)
00061 sscanf(args, "%d:%d:%255[^:]", &priv->w, &priv->h, priv->tb_expr);
00062
00063 if (priv->w <= 0 || priv->h <= 0) {
00064 av_log(ctx, AV_LOG_ERROR, "Non-positive size values are not acceptable.\n");
00065 return AVERROR(EINVAL);
00066 }
00067
00068 return 0;
00069 }
00070
00071 static int config_props(AVFilterLink *outlink)
00072 {
00073 AVFilterContext *ctx = outlink->src;
00074 NullContext *priv = ctx->priv;
00075 AVRational tb;
00076 int ret;
00077 double res;
00078
00079 priv->var_values[VAR_E] = M_E;
00080 priv->var_values[VAR_PHI] = M_PHI;
00081 priv->var_values[VAR_PI] = M_PI;
00082 priv->var_values[VAR_AVTB] = av_q2d(AV_TIME_BASE_Q);
00083
00084 if ((ret = av_expr_parse_and_eval(&res, priv->tb_expr, var_names, priv->var_values,
00085 NULL, NULL, NULL, NULL, NULL, 0, NULL)) < 0) {
00086 av_log(ctx, AV_LOG_ERROR, "Invalid expression '%s' for timebase.\n", priv->tb_expr);
00087 return ret;
00088 }
00089 tb = av_d2q(res, INT_MAX);
00090 if (tb.num <= 0 || tb.den <= 0) {
00091 av_log(ctx, AV_LOG_ERROR,
00092 "Invalid non-positive value for the timebase %d/%d.\n",
00093 tb.num, tb.den);
00094 return AVERROR(EINVAL);
00095 }
00096
00097 outlink->w = priv->w;
00098 outlink->h = priv->h;
00099 outlink->time_base = tb;
00100
00101 av_log(outlink->src, AV_LOG_INFO, "w:%d h:%d tb:%d/%d\n", priv->w, priv->h,
00102 tb.num, tb.den);
00103
00104 return 0;
00105 }
00106
00107 static int request_frame(AVFilterLink *link)
00108 {
00109 return -1;
00110 }
00111
00112 AVFilter avfilter_vsrc_nullsrc = {
00113 .name = "nullsrc",
00114 .description = NULL_IF_CONFIG_SMALL("Null video source, never return images."),
00115
00116 .init = init,
00117 .priv_size = sizeof(NullContext),
00118
00119 .inputs = (AVFilterPad[]) {{ .name = NULL}},
00120
00121 .outputs = (AVFilterPad[]) {
00122 {
00123 .name = "default",
00124 .type = AVMEDIA_TYPE_VIDEO,
00125 .config_props = config_props,
00126 .request_frame = request_frame,
00127 },
00128 { .name = NULL}
00129 },
00130 };