avfilter: add limitdiff video filter

Changelog

@@ -26,6 +26,7 @@ version <next>:
 - GEM Raster image decoder
 - asdr audio filter
 - speex decoder
+- limitdiff video filter
 
 
 version 4.4:

doc/filters.texi

@@ -14488,6 +14488,37 @@ ffmpeg -i main.mpg -i ref.mkv -lavfi "[0:v]settb=AVTB,setpts=PTS-STARTPTS[main];
 @end example
 @end itemize
 
+@section limitdiff
+Apply limited difference filter using second and optionally third video stream.
+
+The filter accepts the following options:
+
+@table @option
+@item threshold
+Set the threshold to use when allowing certain differences between video streams.
+Any absolute difference value lower or exact than this threshold will pick pixel components from
+first video stream.
+
+@item elasticity
+Set the elasticity of soft thresholding when processing video streams.
+This value multiplied with first one sets second threshold.
+Any absolute difference value greater or exact than second threshold will pick pixel components
+from second video stream. For values between those two threshold
+linear interpolation between first and second video stream will be used.
+
+@item reference
+Enable the reference (third) video stream processing. By default is disabled.
+If set, this video stream will be used for calculating absolute difference with first video
+stream.
+
+@item planes
+Specify which planes will be processed. Defaults to all available.
+@end table
+
+@subsection Commands
+
+This filter supports the all above options as @ref{commands} except option @samp{reference}.
+
 @section limiter
 
 Limits the pixel components values to the specified range [min, max].

libavfilter/Makefile

@@ -323,6 +323,7 @@ OBJS-$(CONFIG_LATENCY_FILTER)                += f_latency.o
 OBJS-$(CONFIG_LENSCORRECTION_FILTER)         += vf_lenscorrection.o
 OBJS-$(CONFIG_LENSFUN_FILTER)                += vf_lensfun.o
 OBJS-$(CONFIG_LIBVMAF_FILTER)                += vf_libvmaf.o framesync.o
+OBJS-$(CONFIG_LIMITDIFF_FILTER)              += vf_limitdiff.o framesync.o
 OBJS-$(CONFIG_LIMITER_FILTER)                += vf_limiter.o
 OBJS-$(CONFIG_LOOP_FILTER)                   += f_loop.o
 OBJS-$(CONFIG_LUMAKEY_FILTER)                += vf_lumakey.o

libavfilter/allfilters.c

@@ -308,6 +308,7 @@ extern const AVFilter ff_vf_latency;
 extern const AVFilter ff_vf_lenscorrection;
 extern const AVFilter ff_vf_lensfun;
 extern const AVFilter ff_vf_libvmaf;
+extern const AVFilter ff_vf_limitdiff;
 extern const AVFilter ff_vf_limiter;
 extern const AVFilter ff_vf_loop;
 extern const AVFilter ff_vf_lumakey;

libavfilter/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   8
-#define LIBAVFILTER_VERSION_MINOR  12
+#define LIBAVFILTER_VERSION_MINOR  13
 #define LIBAVFILTER_VERSION_MICRO 100