[FFmpeg-devel] [PATCH 4/4] lavfi/drawtext: implement more generic expansion.

Nicolas George nicolas.george at normalesup.org
Sun Nov 11 18:56:45 CET 2012


The new expansion mechanism uses the %{...} notation.
For compatibility reasons, it must be enabled explicitly,
but a warning is printed if a change is likely to happen.

Signed-off-by: Nicolas George <nicolas.george at normalesup.org>
---
 doc/filters.texi          |   50 ++++++++++++++-
 libavfilter/vf_drawtext.c |  149 +++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 192 insertions(+), 7 deletions(-)

diff --git a/doc/filters.texi b/doc/filters.texi
index eaf0f42..973573e 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -1844,8 +1844,7 @@ libfreetype library.
 To enable compilation of this filter you need to configure FFmpeg with
 @code{--enable-libfreetype}.
 
-The filter also recognizes strftime() sequences in the provided text
-and expands them accordingly. Check the documentation of strftime().
+ at subsection Syntax
 
 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
 separated by ":".
@@ -1865,6 +1864,10 @@ Either a string (e.g. "yellow") or in 0xRRGGBB[AA] format
 (e.g. "0xff00ff"), possibly followed by an alpha specifier.
 The default value of @var{boxcolor} is "white".
 
+ at item compat_expand (or old)
+Use the old strftime-style expansion for the text. It is enabled by default
+for now.
+
 @item draw
 Set an expression which specifies if the text should be drawn. If the
 expression evaluates to 0, the text is not drawn. This is useful for
@@ -2039,6 +2042,43 @@ each other, so you can for example specify @code{y=x/dar}.
 If libavfilter was built with @code{--enable-fontconfig}, then
 @option{fontfile} can be a fontconfig pattern or omitted.
 
+ at subsection Text expansion
+
+If @option{compat_expand} is enabled (which is the default for now),
+the filter also recognizes strftime() sequences in the provided text
+and expands them accordingly. Check the documentation of strftime().
+This feature is deprecated.
+
+If @option{compat_expand} is not enabled, a more general expansion mechanism
+is used.
+
+The backslash character '\', followed by any character, always expand to the
+second character.
+
+Sequence of the form @code{%@{...@}} are expanded. The text between the
+braces is a function name, possibly followed by arguments separated by ':'.
+If the arguments contain special characters or delimiters (':' or '@{'),
+they should be escaped. Note that they probably must also be escaped as the
+value for the @option{text} option in the filter argument string and as the
+filter argument in the filter graph description, and possibly also for the
+shell, that makes up to four levels of escaping; using a text file avoids
+these problems.
+
+The following functions exist:
+
+ at table @command
+
+ at item localtime
+The time at which the filter is running, expressed in the local time zone.
+It can accept an argument: a strftime() format string.
+
+ at item pts
+The timestamp of the current frame, in seconds, with microsecond accuracy.
+
+ at end table
+
+ at subsection Examples
+
 Some examples follow.
 
 @itemize
@@ -2104,6 +2144,12 @@ Use fontconfig to set the font. Note that the colons need to be escaped.
 drawtext='fontfile=Linux Libertine O-40\:style=Semibold:text=FFmpeg'
 @end example
 
+ at item
+Print the date of a real-time encoding (see strftime(3)):
+ at example
+drawtext='fontfile=FreeSans.ttf:compat_expand=0:text=%@{localtime:%a %b %d %Y@}'
+ at end example
+
 @end itemize
 
 For more information about libfreetype, check:
diff --git a/libavfilter/vf_drawtext.c b/libavfilter/vf_drawtext.c
index f9c69ae..e359793 100644
--- a/libavfilter/vf_drawtext.c
+++ b/libavfilter/vf_drawtext.c
@@ -115,6 +115,7 @@ enum var_name {
 
 typedef struct {
     const AVClass *class;
+    int compat_expand;              ///< use old strftime-style expand
     int reinit;                     ///< tells if the filter is being reinited
     uint8_t *fontfile;              ///< font to be used
     uint8_t *text;                  ///< text to be drawn
@@ -181,6 +182,8 @@ static const AVOption drawtext_options[]= {
 {"tabsize",  "set tab size",         OFFSET(tabsize),            AV_OPT_TYPE_INT,    {.i64=4},     0,        INT_MAX , FLAGS},
 {"basetime", "set base time",        OFFSET(basetime),           AV_OPT_TYPE_INT64,  {.i64=AV_NOPTS_VALUE}, INT64_MIN, INT64_MAX , FLAGS},
 {"draw",     "if false do not draw", OFFSET(draw_expr),          AV_OPT_TYPE_STRING, {.str="1"},   CHAR_MIN, CHAR_MAX, FLAGS},
+{"compat_expand", "use old strftime-style expand", OFFSET(compat_expand), AV_OPT_TYPE_INT, {.i64=1},      0,        1, FLAGS},
+{"old",           "use old strftime-style expand", OFFSET(compat_expand), AV_OPT_TYPE_INT, {.i64=1},      0,        1, FLAGS},
 {"timecode", "set initial timecode", OFFSET(tc_opt_string),      AV_OPT_TYPE_STRING, {.str=NULL},  CHAR_MIN, CHAR_MAX, FLAGS},
 {"tc24hmax", "set 24 hours max (timecode only)", OFFSET(tc24hmax), AV_OPT_TYPE_INT,  {.i64=0},            0,        1, FLAGS},
 {"timecode_rate", "set rate (timecode only)", OFFSET(tc_rate),   AV_OPT_TYPE_RATIONAL, {.dbl=0},          0,  INT_MAX, FLAGS},
@@ -484,6 +487,10 @@ static av_cold int init(AVFilterContext *ctx, const char *args)
     }
     dtext->tabsize *= glyph->advance;
 
+    if (dtext->compat_expand &&
+        (strchr(dtext->text, '%') || strchr(dtext->text, '\\')))
+        av_log(ctx, AV_LOG_WARNING, "Compat expand is deprecated.\n");
+
     av_bprint_init(&dtext->expanded_text, 0, AV_BPRINT_SIZE_UNLIMITED);
 
     return 0;
@@ -585,6 +592,138 @@ static int command(AVFilterContext *ctx, const char *cmd, const char *arg, char
     return AVERROR(ENOSYS);
 }
 
+static int func_pts(AVFilterContext *ctx, AVBPrint *bp,
+                    char *fct, char **argv, unsigned argc, int tag)
+{
+    DrawTextContext *dtext = ctx->priv;
+
+    av_bprintf(bp, "%.6f", dtext->var_values[VAR_T]);
+    return 0;
+}
+
+#if !HAVE_LOCALTIME_R
+static void localtime_r(const time_t *t, struct tm *tm)
+{
+    *tm = localtime(t);
+}
+#endif
+
+static int func_strftime(AVFilterContext *ctx, AVBPrint *bp,
+                         char *fct, char **argv, unsigned argc, int tag)
+{
+    const char *fmt = argc ? argv[0] : "%Y-%m-%d %H:%M:%S";
+    time_t now;
+    struct tm tm;
+
+    time(&now);
+    localtime_r(&now, &tm);
+    av_bprint_strftime(bp, fmt, &tm);
+    return 0;
+}
+
+static const struct drawtext_function {
+    const char *name;
+    unsigned argc_min, argc_max;
+    int tag;
+    int (*func)(AVFilterContext *, AVBPrint *, char *, char **, unsigned, int);
+} functions[] = {
+    { "pts",       0, 0, 0,   func_pts      },
+    { "localtime", 0, 1, 'L', func_strftime },
+};
+
+static int eval_function(AVFilterContext *ctx, AVBPrint *bp, char *fct,
+                         char **argv, unsigned argc)
+{
+    unsigned i;
+
+    for (i = 0; i < FF_ARRAY_ELEMS(functions); i++) {
+        if (strcmp(fct, functions[i].name))
+            continue;
+        if (argc < functions[i].argc_min) {
+            av_log(ctx, AV_LOG_ERROR, "%%{%s} requires at least %d arguments\n",
+                   fct, functions[i].argc_min);
+            return AVERROR(EINVAL);
+        }
+        if (argc > functions[i].argc_max) {
+            av_log(ctx, AV_LOG_ERROR, "%%{%s} requires at most %d arguments\n",
+                   fct, functions[i].argc_max);
+            return AVERROR(EINVAL);
+        }
+        break;
+    }
+    if (i >= FF_ARRAY_ELEMS(functions)) {
+        av_log(ctx, AV_LOG_ERROR, "%%{%s} is not known\n", fct);
+        return AVERROR(EINVAL);
+    }
+    return functions[i].func(ctx, bp, fct, argv, argc, functions[i].tag);
+}
+
+static int expand_function(AVFilterContext *ctx, AVBPrint *bp, char **rtext)
+{
+    const char *text = *rtext;
+    char *argv[16] = { NULL };
+    unsigned argc = 0, i;
+    int ret;
+
+    if (*text != '{') {
+        av_log(ctx, AV_LOG_ERROR, "Stray %% near '%s'\n", text);
+        return AVERROR(EINVAL);
+    }
+    text++;
+    while (1) {
+        if (!(argv[argc++] = av_get_token(&text, ":}"))) {
+            ret = AVERROR(ENOMEM);
+            goto end;
+        }
+        if (!*text) {
+            av_log(ctx, AV_LOG_ERROR, "Unterminated %%{} near '%s'\n", *rtext);
+            ret = AVERROR(EINVAL);
+            goto end;
+        }
+        if (argc == FF_ARRAY_ELEMS(argv))
+            av_freep(&argv[--argc]); /* error will be caught later */
+        if (*text == '}')
+            break;
+        text++;
+    }
+
+    if ((ret = eval_function(ctx, bp, argv[0], argv + 1, argc - 1)) < 0)
+        goto end;
+    ret = 0;
+    *rtext = (char *)text + 1;
+
+end:
+    for (i = 0; i < argc; i++)
+        av_freep(&argv[i]);
+    return ret;
+}
+
+static int expand_text(AVFilterContext *ctx)
+{
+    DrawTextContext *dtext = ctx->priv;
+    char *text = dtext->text;
+    AVBPrint *bp = &dtext->expanded_text;
+    int ret;
+
+    av_bprint_clear(bp);
+    while (*text) {
+        if (*text == '\\' && text[1]) {
+            av_bprint_chars(bp, text[1], 1);
+            text += 2;
+        } else if (*text == '%') {
+            text++;
+            if ((ret = expand_function(ctx, bp, &text)) < 0)
+                return ret;
+        } else {
+            av_bprint_chars(bp, *text, 1);
+            text++;
+        }
+    }
+    if (!av_bprint_is_complete(bp))
+        return AVERROR(ENOMEM);
+    return 0;
+}
+
 static int draw_glyphs(DrawTextContext *dtext, AVFilterBufferRef *picref,
                        int width, int height, const uint8_t rgbcolor[4], FFDrawColor *color, int x, int y)
 {
@@ -648,13 +787,13 @@ static int draw_text(AVFilterContext *ctx, AVFilterBufferRef *picref,
     if(dtext->basetime != AV_NOPTS_VALUE)
         now= picref->pts*av_q2d(ctx->inputs[0]->time_base) + dtext->basetime/1000000;
 
-#if HAVE_LOCALTIME_R
+    if (dtext->compat_expand) {
     localtime_r(&now, &ltime);
-#else
-    if(strchr(dtext->text, '%'))
-        ltime= *localtime(&now);
-#endif
     av_bprint_strftime(bp, dtext->text, &ltime);
+    } else {
+        if ((ret = expand_text(ctx)) < 0)
+            return ret;
+    }
 
     if (dtext->tc_opt_string) {
         char tcbuf[AV_TIMECODE_STR_SIZE];
-- 
1.7.10.4



More information about the ffmpeg-devel mailing list