avfilter: add deband filter

Signed-off-by: Paul B Mahol <onemda@gmail.com>

Changelog

@@ -20,6 +20,7 @@ version <next>:
 - Dynamic Audio Normalizer as dynaudnorm filter
 - Reverse filter
 - Random filter
+- deband filter
 
 
 version 2.7:

doc/filters.texi

@@ -3878,6 +3878,43 @@ Violent denoise using a block size of @code{16x16}:
 dctdnoiz=15:n=4
 @end example
 
+@section deband
+
+Remove banding artifacts from input video.
+It works by replacing banded pixels with average value of referenced pixels.
+
+The filter accepts the following options:
+
+@table @option
+@item 1thr
+@item 2thr
+@item 3thr
+@item 4thr
+Set banding detection threshold for each plane. Default is 0.02.
+Valid range is 0.00003 to 0.5.
+If difference between current pixel and reference pixel is less than threshold,
+it will be considered as banded.
+
+@item range, r
+Banding detection range in pixels. Default is 16. If positive, random number
+in range 0 to set value will be used. If negative, exact absolute value
+will be used.
+The range defines square of four pixels around current pixel.
+
+@item direction, d
+Set direction in radians from which four pixel will be compared. If positive,
+random direction from 0 to set direction will be picked. If negative, exact of
+absolute value will be picked. For example direction 0, -PI or -2*PI radians
+will pick only pixels on same row and -PI/2 will pick only pixels on same
+column.
+
+@item blur
+If enabled, current pixel is compared with average value of all four
+surrounding pixels. The default is enabled. If disabled current pixel is
+compared with all four surrounding pixels. The pixel is considered banded
+if only all four differences with surrounding pixels are less than threshold.
+@end table
+
 @anchor{decimate}
 @section decimate
 

libavfilter/Makefile

@@ -112,6 +112,7 @@ OBJS-$(CONFIG_CROP_FILTER)                   += vf_crop.o
 OBJS-$(CONFIG_CROPDETECT_FILTER)             += vf_cropdetect.o
 OBJS-$(CONFIG_CURVES_FILTER)                 += vf_curves.o
 OBJS-$(CONFIG_DCTDNOIZ_FILTER)               += vf_dctdnoiz.o
+OBJS-$(CONFIG_DEBAND_FILTER)                 += vf_deband.o
 OBJS-$(CONFIG_DECIMATE_FILTER)               += vf_decimate.o
 OBJS-$(CONFIG_DEFLATE_FILTER)                += vf_neighbor.o
 OBJS-$(CONFIG_DEJUDDER_FILTER)               += vf_dejudder.o

libavfilter/allfilters.c

@@ -128,6 +128,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER(CROPDETECT,     cropdetect,     vf);
     REGISTER_FILTER(CURVES,         curves,         vf);
     REGISTER_FILTER(DCTDNOIZ,       dctdnoiz,       vf);
+    REGISTER_FILTER(DEBAND,         deband,         vf);
     REGISTER_FILTER(DECIMATE,       decimate,       vf);
     REGISTER_FILTER(DEFLATE,        deflate,        vf);
     REGISTER_FILTER(DEJUDDER,       dejudder,       vf);

libavfilter/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  5
-#define LIBAVFILTER_VERSION_MINOR  25
+#define LIBAVFILTER_VERSION_MINOR  27
 #define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \