[FFmpeg-devel] [PATCH 2/7] Extend the nullsrc source, make it accepts a parameter for specifying the timebase (useful for debugging timebase configuration issues).

[Stefano Sabatini]

---
 doc/filters.texi           |   12 ++++++---
 libavfilter/vsrc_nullsrc.c |   53 +++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 58 insertions(+), 7 deletions(-)

diff --git a/doc/filters.texi b/doc/filters.texi
index 68dcf7f..3c3285e 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -652,11 +652,15 @@ Null video source, never return images. It is mainly useful as a
 template and to be employed in analysis / debugging tools.
 
 It accepts as optional parameter a string of the form
- at var{width}:@var{height}, where @var{width} and @var{height} specify the size of
-the configured source.
+ at var{width}:@var{height}:@var{timebase}.
 
-The default values of @var{width} and @var{height} are respectively 352
-and 288 (corresponding to the CIF size format).
+ at var{width} and @var{height} specify the size of the configured
+source. The default values of @var{width} and @var{height} are
+respectively 352 and 288 (corresponding to the CIF size format).
+
+ at var{timebase} specifies an arithmetic expression representing a
+timebase. The expression can contain the constants "PI", "E", "PHI",
+"AVTB" (the default timebase), and default to the value "AVTB".
 
 @c man end VIDEO SOURCES
 
diff --git a/libavfilter/vsrc_nullsrc.c b/libavfilter/vsrc_nullsrc.c
index f319ceb..80978c8 100644
--- a/libavfilter/vsrc_nullsrc.c
+++ b/libavfilter/vsrc_nullsrc.c
@@ -21,10 +21,32 @@
  * null video source
  */
 
+#include "libavutil/avstring.h"
+#include "libavutil/eval.h"
+#include "libavcore/parseutils.h"
 #include "avfilter.h"
 
+static const char *var_names[] = {
+    "E",
+    "PHI",
+    "PI",
+    "AVTB",   /* default timebase 1/AV_TIME_BASE */
+    NULL
+};
+
+enum var_name {
+    VAR_E,
+    VAR_PHI,
+    VAR_PI,
+    VAR_AVTB,
+    VAR_INTB,
+    VAR_VARS_NB
+};
+
 typedef struct {
     int w, h;
+    char tb_expr[256];
+    double var_values[VAR_VARS_NB];
 } NullContext;
 
 static int init(AVFilterContext *ctx, const char *args, void *opaque)
@@ -33,9 +55,10 @@ static int init(AVFilterContext *ctx, const char *args, void *opaque)
 
     priv->w = 352;
     priv->h = 288;
+    av_strlcpy(priv->tb_expr, "AVTB", sizeof(priv->tb_expr));
 
     if (args)
-        sscanf(args, "%d:%d", &priv->w, &priv->h);
+        sscanf(args, "%d:%d:%255s", &priv->w, &priv->h, priv->tb_expr);
 
     if (priv->w <= 0 || priv->h <= 0) {
         av_log(ctx, AV_LOG_ERROR, "Non-positive size values are not acceptable.\n");
@@ -47,12 +70,36 @@ static int init(AVFilterContext *ctx, const char *args, void *opaque)
 
 static int config_props(AVFilterLink *outlink)
 {
-    NullContext *priv = outlink->src->priv;
+    AVFilterContext *ctx = outlink->src;
+    NullContext *priv = ctx->priv;
+    AVRational tb;
+    int ret;
+    double res;
+
+    priv->var_values[VAR_E]    = M_E;
+    priv->var_values[VAR_PHI]  = M_PHI;
+    priv->var_values[VAR_PI]   = M_PI;
+    priv->var_values[VAR_AVTB] = av_q2d(AV_TIME_BASE_Q);
+
+    if ((ret = av_parse_and_eval_expr(&res, priv->tb_expr, var_names, priv->var_values,
+                                      NULL, NULL, NULL, NULL, NULL, 0, NULL)) < 0) {
+        av_log(ctx, AV_LOG_ERROR, "Invalid expression '%s' for timebase.\n", priv->tb_expr);
+        return ret;
+    }
+    tb = av_d2q(res, INT_MAX);
+    if (tb.num <= 0 || tb.den <= 0) {
+        av_log(ctx, AV_LOG_ERROR,
+               "Invalid non-positive values for the timebase %d/%d.\n",
+               tb.num, tb.den);
+        return AVERROR(EINVAL);
+    }
 
     outlink->w = priv->w;
     outlink->h = priv->h;
+    outlink->time_base = tb;
 
-    av_log(outlink->src, AV_LOG_INFO, "w:%d h:%d\n", priv->w, priv->h);
+    av_log(outlink->src, AV_LOG_INFO, "w:%d h:%d tb:%d/%d\n", priv->w, priv->h,
+           tb.num, tb.den);
 
     return 0;
 }
-- 
1.7.1