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lavfi/drawtext: add support to expansion of generic expressions

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This commit is contained in:
Stefano Sabatini 2012-11-27 11:27:12 +01:00
parent 2cfa6fd025
commit 2ac6a3d1bf
3 changed files with 33 additions and 1 deletions
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10
doc/filters.texi
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@ -2075,6 +2075,16 @@ The following functions are available:
@table @command
@item expr, e
The expression evaluation result.
It must take one argument specifying the expression to be evaluated,
which accepts the same constants and functions as the @var{x} and
@var{y} values. Note that not all constants should be used, for
example the text size is not known when evaluating the expression, so
the constants @var{text_w} and @var{text_h} will have an undefined
value.
@item gmtime
The time at which the filter is running, expressed in UTC.
It can accept an argument: a strftime() format string.

2
libavfilter/version.h
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@ -30,7 +30,7 @@
#define LIBAVFILTER_VERSION_MAJOR 3
#define LIBAVFILTER_VERSION_MINOR 23
#define LIBAVFILTER_VERSION_MICRO 103
#define LIBAVFILTER_VERSION_MICRO 104
#define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
LIBAVFILTER_VERSION_MINOR, \

22
libavfilter/vf_drawtext.c
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@ -643,12 +643,34 @@ static int func_strftime(AVFilterContext *ctx, AVBPrint *bp,
return 0;
}
static int func_eval_expr(AVFilterContext *ctx, AVBPrint *bp,
char *fct, unsigned argc, char **argv, int tag)
{
DrawTextContext *dtext = ctx->priv;
double res;
int ret;
ret = av_expr_parse_and_eval(&res, argv[0], var_names, dtext->var_values,
NULL, NULL, fun2_names, fun2,
&dtext->prng, 0, ctx);
if (ret < 0)
av_log(ctx, AV_LOG_ERROR,
"Expression '%s' for the expr text expansion function is not valid\n",
argv[0]);
else
av_bprintf(bp, "%f", res);
return ret;
}
static const struct drawtext_function {
const char *name;
unsigned argc_min, argc_max;
int tag; /** opaque argument to func */
int (*func)(AVFilterContext *, AVBPrint *, char *, unsigned, char **, int);
} functions[] = {
{ "expr", 1, 1, 0, func_eval_expr },
{ "e", 1, 1, 0, func_eval_expr },
{ "pts", 0, 0, 0, func_pts },
{ "gmtime", 0, 1, 'G', func_strftime },
{ "localtime", 0, 1, 'L', func_strftime },