lavfi/blackframe: add support for named options

doc/filters.texi

@@ -1801,16 +1801,22 @@ the position in the file if known or -1 and the timestamp in seconds.
 In order to display the output lines, you need to set the loglevel at
 least to the AV_LOG_INFO value.
 
-The filter accepts the syntax:
-@example
-blackframe[=@var{amount}:[@var{threshold}]]
-@end example
+The filter accepts parameters as a list of @var{key}=@var{value}
+pairs, separated by ":". If the key of the first options is omitted,
+the arguments are interpreted according to the syntax
+blackframe[=@var{amount}[:@var{threshold}]].
 
-@var{amount} is the percentage of the pixels that have to be below the
-threshold, and defaults to 98.
+A description of the accepted options follows.
 
-@var{threshold} is the threshold below which a pixel value is
-considered black, and defaults to 32.
+@table @option
+@item amount
+Set the percentage of pixels that have to be below the
+threshold to enable black detection. Default value is 98.
+
+@item threshold
+Set the threshold below which a pixel value is considered
+black. Default value is 32.
+@end table
 
 @section blend
 

libavfilter/version.h

@@ -30,7 +30,7 @@
 
 #define LIBAVFILTER_VERSION_MAJOR  3
 #define LIBAVFILTER_VERSION_MINOR  47
-#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_blackframe.c

@@ -31,6 +31,7 @@
 #include <inttypes.h>
 
 #include "libavutil/internal.h"
+#include "libavutil/opt.h"
 #include "avfilter.h"
 #include "internal.h"
 #include "formats.h"
@@ -38,6 +39,7 @@
 #include "video.h"
 
 typedef struct {
+    const AVClass *class;
     unsigned int bamount; ///< black amount
     unsigned int bthresh; ///< black threshold
     unsigned int frame;   ///< frame number
@@ -45,6 +47,17 @@ typedef struct {
     unsigned int last_keyframe; ///< frame number of the last received key-frame
 } BlackFrameContext;
 
+#define OFFSET(x) offsetof(BlackFrameContext, x)
+#define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
+
+static const AVOption blackframe_options[] = {
+    { "amount", "set least percentual amount of pixels below the black threshold enabling black detection", OFFSET(bamount), AV_OPT_TYPE_INT, {.i64=98}, 0, 100, FLAGS },
+    { "thresh", "set threshold below which a pixel value is considered black", OFFSET(bthresh), AV_OPT_TYPE_INT, {.i64=32}, 0, 255, FLAGS },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(blackframe);
+
 static int query_formats(AVFilterContext *ctx)
 {
     static const enum AVPixelFormat pix_fmts[] = {
@@ -60,27 +73,27 @@ static int query_formats(AVFilterContext *ctx)
 static av_cold int init(AVFilterContext *ctx, const char *args)
 {
     BlackFrameContext *blackframe = ctx->priv;
+    static const char *shorthand[] = { "amount", "thresh", NULL };
+    int ret;
 
-    blackframe->bamount = 98;
-    blackframe->bthresh = 32;
-    blackframe->nblack = 0;
-    blackframe->frame = 0;
-    blackframe->last_keyframe = 0;
+    blackframe->class = &blackframe_class;
+    av_opt_set_defaults(blackframe);
 
-    if (args)
-        sscanf(args, "%u:%u", &blackframe->bamount, &blackframe->bthresh);
+    if ((ret = av_opt_set_from_string(blackframe, args, shorthand, "=", ":")) < 0)
+        return ret;
 
     av_log(ctx, AV_LOG_VERBOSE, "bamount:%u bthresh:%u\n",
            blackframe->bamount, blackframe->bthresh);
 
-    if (blackframe->bamount > 100 || blackframe->bthresh > 255) {
-        av_log(ctx, AV_LOG_ERROR, "Too big value for bamount (max is 100) or bthresh (max is 255)\n");
-        return AVERROR(EINVAL);
-    }
-
     return 0;
 }
 
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    BlackFrameContext *blackframe = ctx->priv;
+    av_opt_free(blackframe);
+}
+
 static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
 {
     AVFilterContext *ctx = inlink->dst;
@@ -135,10 +148,13 @@ AVFilter avfilter_vf_blackframe = {
 
     .priv_size = sizeof(BlackFrameContext),
     .init      = init,
+    .uninit    = uninit,
 
     .query_formats = query_formats,
 
     .inputs    = avfilter_vf_blackframe_inputs,
 
     .outputs   = avfilter_vf_blackframe_outputs,
+
+    .priv_class = &blackframe_class,
 };