avfilter/vf_median: implement percentile option

Author: richardpl

doc/filters.texi

@@ -13289,6 +13289,11 @@ Set which planes to process. Default is @code{15}, which is all available planes
 Set vertical radius size. Default value is @code{0}.
 Allowed range is integer from 0 to 127.
 If it is 0, value will be picked from horizontal @code{radius} option.
+
+@item percentile
+Set median percentile. Default value is @code{0.5}.
+Default value of @code{0.5} will pick always median values, while @code{0} will pick
+minimum values, and @code{1} maximum values.
 @end table
 
 @subsection Commands

libavfilter/median.h

@@ -31,6 +31,7 @@ typedef struct MedianContext {
     int planes;
     int radius;
     int radiusV;
+    float percentile;
 
     int planewidth[4];
     int planeheight[4];

libavfilter/vf_median.c

@@ -60,6 +60,7 @@ static const AVOption median_options[] = {
     { "radius", "set median radius",    OFFSET(radius), AV_OPT_TYPE_INT,   {.i64=1},     1,  127, FLAGS },
     { "planes", "set planes to filter", OFFSET(planes), AV_OPT_TYPE_INT,   {.i64=0xF},   0,  0xF, FLAGS },
     { "radiusV", "set median vertical radius", OFFSET(radiusV), AV_OPT_TYPE_INT, {.i64=0},0, 127, FLAGS },
+    { "percentile", "set median percentile", OFFSET(percentile), AV_OPT_TYPE_FLOAT, {.dbl=.5}, 0., 1., FLAGS },
     { NULL }
 };
 
@@ -127,7 +128,7 @@ static void check_params(MedianContext *s, AVFilterLink *inlink)
         }
     }
 
-    s->t = 2 * s->radius * s->radiusV + 2 * s->radius;
+    s->t = (2 * s->radius * s->radiusV + s->radiusV + s->radius) * 2.f * s->percentile;
 }
 
 static int config_input(AVFilterLink *inlink)