lavfi/setfield: add support to named options and introspection

doc/filters.texi

@@ -3632,7 +3632,10 @@ output frames. It does not change the input frame, but only sets the
 corresponding property, which affects how the frame is treated by
 following filters (e.g. @code{fieldorder} or @code{yadif}).
 
-It accepts a string parameter, which can assume the following values:
+This filter accepts a single option @option{mode}, which can be
+specified either by setting @code{mode=VALUE} either setting the
+value alone. Available values are:
+
 @table @samp
 @item auto
 Keep the same field property.

libavfilter/version.h

@@ -30,7 +30,7 @@
 
 #define LIBAVFILTER_VERSION_MAJOR  3
 #define LIBAVFILTER_VERSION_MINOR  26
-#define LIBAVFILTER_VERSION_MICRO 100
+#define LIBAVFILTER_VERSION_MICRO 101
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \

libavfilter/vf_setfield.c

@@ -23,6 +23,7 @@
  * set field order
  */
 
+#include "libavutil/opt.h"
 #include "avfilter.h"
 #include "internal.h"
 #include "video.h"
@@ -35,39 +36,39 @@ enum SetFieldMode {
 };
 
 typedef struct {
+    const AVClass *class;
     enum SetFieldMode mode;
 } SetFieldContext;
 
+#define OFFSET(x) offsetof(SetFieldContext, x)
+#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
+
+static const AVOption setfield_options[] = {
+    {"mode", "select interlace mode", OFFSET(mode), AV_OPT_TYPE_INT, {.i64=MODE_AUTO}, -1, MODE_PROG, FLAGS, "mode"},
+    {"auto", "keep the same input field",  0, AV_OPT_TYPE_CONST, {.i64=MODE_AUTO}, INT_MIN, INT_MAX, FLAGS, "mode"},
+    {"bff",  "mark as bottom-field-first", 0, AV_OPT_TYPE_CONST, {.i64=MODE_BFF},  INT_MIN, INT_MAX, FLAGS, "mode"},
+    {"tff",  "mark as top-field-first",    0, AV_OPT_TYPE_CONST, {.i64=MODE_TFF},  INT_MIN, INT_MAX, FLAGS, "mode"},
+    {"prog", "mark as progressive",        0, AV_OPT_TYPE_CONST, {.i64=MODE_PROG}, INT_MIN, INT_MAX, FLAGS, "mode"},
+    {NULL}
+};
+
+AVFILTER_DEFINE_CLASS(setfield);
+
 static av_cold int init(AVFilterContext *ctx, const char *args)
 {
     SetFieldContext *setfield = ctx->priv;
+    static const char *shorthand[] = { "mode", NULL };
 
-    setfield->mode = MODE_AUTO;
-
-    if (args) {
-        char c;
-        if (sscanf(args, "%d%c", &setfield->mode, &c) != 1) {
-            if      (!strcmp("tff",  args)) setfield->mode = MODE_TFF;
-            else if (!strcmp("bff",  args)) setfield->mode = MODE_BFF;
-            else if (!strcmp("prog", args)) setfield->mode = MODE_PROG;
-            else if (!strcmp("auto", args)) setfield->mode = MODE_AUTO;
-            else {
-                av_log(ctx, AV_LOG_ERROR, "Invalid argument '%s'\n", args);
-                return AVERROR(EINVAL);
-            }
-        } else {
-            if (setfield->mode < -1 || setfield->mode > 1) {
-                av_log(ctx, AV_LOG_ERROR,
-                       "Provided integer value %d must be included between -1 and +1\n",
-                       setfield->mode);
-                return AVERROR(EINVAL);
-            }
-            av_log(ctx, AV_LOG_WARNING,
-                   "Using -1/0/1 is deprecated, use auto/tff/bff/prog\n");
-        }
-    }
+    setfield->class = &setfield_class;
+    av_opt_set_defaults(setfield);
 
-    return 0;
+    return av_opt_set_from_string(setfield, args, shorthand, "=", ":");
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    SetFieldContext *setfield = ctx->priv;
+    av_opt_free(setfield);
 }
 
 static int filter_frame(AVFilterLink *inlink, AVFilterBufferRef *picref)
@@ -105,8 +106,10 @@ AVFilter avfilter_vf_setfield = {
     .name      = "setfield",
     .description = NULL_IF_CONFIG_SMALL("Force field for the output video frame."),
     .init      = init,
+    .uninit    = uninit,
 
     .priv_size = sizeof(SetFieldContext),
     .inputs    = setfield_inputs,
     .outputs   = setfield_outputs,
+    .priv_class = &setfield_class,
 };