vf_setpts: switch to an AVOptions-based system.

doc/filters.texi

@@ -1895,8 +1895,17 @@ See also the @ref{setsar} filter documentation.
 
 Change the PTS (presentation timestamp) of the input video frames.
 
-Accept in input an expression evaluated through the eval API, which
-can contain the following constants:
+This filter accepts the following options:
+
+@table @option
+
+@item expr
+The expression which is evaluated for each frame to construct its timestamp.
+
+@end table
+
+The expression is evaluated through the eval API and can contain the following
+constants:
 
 @table @option
 @item PTS
@@ -1938,10 +1947,10 @@ Some examples follow:
 
 @example
 # start counting PTS from zero
-setpts=PTS-STARTPTS
+setpts=expr=PTS-STARTPTS
 
 # fast motion
-setpts=0.5*PTS
+setpts=expr=0.5*PTS
 
 # slow motion
 setpts=2.0*PTS

libavfilter/vf_setpts.c

@@ -29,6 +29,7 @@
 #include "libavutil/eval.h"
 #include "libavutil/internal.h"
 #include "libavutil/mathematics.h"
+#include "libavutil/opt.h"
 #include "libavutil/time.h"
 #include "avfilter.h"
 #include "internal.h"
@@ -67,6 +68,8 @@ enum var_name {
 };
 
 typedef struct {
+    const AVClass *class;
+    char *expr_str;
     AVExpr *expr;
     double var_values[VAR_VARS_NB];
 } SetPTSContext;
@@ -76,9 +79,9 @@ static av_cold int init(AVFilterContext *ctx, const char *args)
     SetPTSContext *setpts = ctx->priv;
     int ret;
 
-    if ((ret = av_expr_parse(&setpts->expr, args ? args : "PTS",
+    if ((ret = av_expr_parse(&setpts->expr, setpts->expr_str,
                              var_names, NULL, NULL, NULL, NULL, 0, ctx)) < 0) {
-        av_log(ctx, AV_LOG_ERROR, "Error while parsing expression '%s'\n", args);
+        av_log(ctx, AV_LOG_ERROR, "Error while parsing expression '%s'\n", setpts->expr_str);
         return ret;
     }
 
@@ -145,6 +148,20 @@ static av_cold void uninit(AVFilterContext *ctx)
     setpts->expr = NULL;
 }
 
+#define OFFSET(x) offsetof(SetPTSContext, x)
+#define FLAGS AV_OPT_FLAG_VIDEO_PARAM
+static const AVOption options[] = {
+    { "expr", "Expression determining the frame timestamp", OFFSET(expr_str), AV_OPT_TYPE_STRING, { .str = "PTS" }, .flags = FLAGS },
+    { NULL },
+};
+
+static const AVClass setpts_class = {
+    .class_name = "setpts",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
 static const AVFilterPad avfilter_vf_setpts_inputs[] = {
     {
         .name             = "default",
@@ -171,6 +188,7 @@ AVFilter avfilter_vf_setpts = {
     .uninit    = uninit,
 
     .priv_size = sizeof(SetPTSContext),
+    .priv_class = &setpts_class,
 
     .inputs    = avfilter_vf_setpts_inputs,
     .outputs   = avfilter_vf_setpts_outputs,