avfilter: add framerate video filter

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

Changelog

@@ -37,6 +37,7 @@ version <next>:
 - hstack and vstack filter
 - Support DNx100 (1440x1080@8)
 - VAAPI hevc hwaccel
+- framerate filter
 
 
 version 2.7:

doc/filters.texi

@@ -6015,6 +6015,51 @@ ffmpeg -i LEFT -i RIGHT -filter_complex framepack=frameseq OUTPUT
 ffmpeg -i LEFT -i RIGHT -filter_complex [0:v]scale=w=iw/2[left],[1:v]scale=w=iw/2[right],[left][right]framepack=sbs OUTPUT
 @end example
 
+@section framerate
+
+Change the frame rate by interpolating new video output frames from the source
+frames.
+
+This filter is not designed to function correctly with interlaced media. If
+you wish to change the frame rate of interlaced media then you are required
+to deinterlace before this filter and re-interlace after this filter.
+
+A description of the accepted options follows.
+
+@table @option
+@item fps
+Specify the output frames per second. This option can also be specified
+as a value alone. The default is @code{50}.
+
+@item interp_start
+Specify the start of a range where the output frame will be created as a
+linear interpolation of two frames. The range is [@code{0}-@code{255}],
+the default is @code{15}.
+
+@item interp_end
+Specify the end of a range where the output frame will be created as a
+linear interpolation of two frames. The range is [@code{0}-@code{255}],
+the default is @code{240}.
+
+@item scene
+Specify the level at which a scene change is detected as a value between
+0 and 100 to indicate a new scene; a low value reflects a low
+probability for the current frame to introduce a new scene, while a higher
+value means the current frame is more likely to be one.
+The default is @code{7}.
+
+@item flags
+Specify flags influencing the filter process.
+
+Available value for @var{flags} is:
+
+@table @option
+@item scene_change_detect, scd
+Enable scene change detection using the value of the option @var{scene}.
+This flag is enabled by default.
+@end table
+@end table
+
 @section framestep
 
 Select one frame every N-th frame.

libavfilter/Makefile

@@ -142,6 +142,7 @@ OBJS-$(CONFIG_FIND_RECT_FILTER)              += vf_find_rect.o lavfutils.o
 OBJS-$(CONFIG_FORMAT_FILTER)                 += vf_format.o
 OBJS-$(CONFIG_FPS_FILTER)                    += vf_fps.o
 OBJS-$(CONFIG_FRAMEPACK_FILTER)              += vf_framepack.o
+OBJS-$(CONFIG_FRAMERATE_FILTER)              += vf_framerate.o
 OBJS-$(CONFIG_FRAMESTEP_FILTER)              += vf_framestep.o
 OBJS-$(CONFIG_FREI0R_FILTER)                 += vf_frei0r.o
 OBJS-$(CONFIG_FSPP_FILTER)                   += vf_fspp.o

libavfilter/allfilters.c

@@ -158,6 +158,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER(FORMAT,         format,         vf);
     REGISTER_FILTER(FPS,            fps,            vf);
     REGISTER_FILTER(FRAMEPACK,      framepack,      vf);
+    REGISTER_FILTER(FRAMERATE,      framerate,      vf);
     REGISTER_FILTER(FRAMESTEP,      framestep,      vf);
     REGISTER_FILTER(FREI0R,         frei0r,         vf);
     REGISTER_FILTER(FSPP,           fspp,           vf);

libavfilter/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  5
-#define LIBAVFILTER_VERSION_MINOR  38
+#define LIBAVFILTER_VERSION_MINOR  39
 #define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \