lavfi: port 2xsai filter from libmpcodecs

Partially based on the port by Niel van der Westhuizen
<nielkie@gmail.com>, done for GCI 2010. Same output as the original
filter and as fast.

See thread:
Subject: [FFmpeg-devel] [PATCH] Port MPlayer 2xSaI filter to libavfilter
Date: Thu, 25 Nov 2010 01:31:24 +1000

Changelog

@@ -25,6 +25,7 @@ version next:
 - drop support for ffmpeg without libavfilter
 - drawtext video filter: fontconfig support
 - ffmpeg -benchmark_all option
+- super2xsai filter ported from libmpcodecs
 
 
 version 0.10:

configure

@@ -1692,6 +1692,7 @@ ocv_filter_deps="libopencv"
 pan_filter_deps="swresample"
 removelogo_filter_deps="avcodec avformat swscale"
 scale_filter_deps="swscale"
+super2xsai_filter_deps="gpl"
 tinterlace_filter_deps="gpl"
 yadif_filter_deps="gpl"
 

doc/filters.texi

@@ -2716,6 +2716,13 @@ For example:
 will create two separate outputs from the same input, one cropped and
 one padded.
 
+@section super2xsai
+
+Scale the input by 2x and smooth using the Super2xSaI (Scale and
+Interpolate) pixel art scaling algorithm.
+
+Useful for enlarging pixel art images without reducing sharpness.
+
 @section swapuv
 Swap U & V plane.
 

libavfilter/Makefile

@@ -94,6 +94,7 @@ OBJS-$(CONFIG_SETTB_FILTER)                  += vf_settb.o
 OBJS-$(CONFIG_SHOWINFO_FILTER)               += vf_showinfo.o
 OBJS-$(CONFIG_SLICIFY_FILTER)                += vf_slicify.o
 OBJS-$(CONFIG_SPLIT_FILTER)                  += vf_split.o
+OBJS-$(CONFIG_SUPER2XSAI_FILTER)             += vf_super2xsai.o
 OBJS-$(CONFIG_SWAPUV_FILTER)                 += vf_swapuv.o
 OBJS-$(CONFIG_THUMBNAIL_FILTER)              += vf_thumbnail.o
 OBJS-$(CONFIG_TILE_FILTER)                   += vf_tile.o

libavfilter/allfilters.c

@@ -99,6 +99,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER (SHOWINFO,    showinfo,    vf);
     REGISTER_FILTER (SLICIFY,     slicify,     vf);
     REGISTER_FILTER (SPLIT,       split,       vf);
+    REGISTER_FILTER (SUPER2XSAI,  super2xsai,  vf);
     REGISTER_FILTER (SWAPUV,      swapuv,      vf);
     REGISTER_FILTER (THUMBNAIL,   thumbnail,   vf);
     REGISTER_FILTER (TILE,        tile,        vf);

libavfilter/version.h

@@ -29,7 +29,7 @@
 #include "libavutil/avutil.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  2
-#define LIBAVFILTER_VERSION_MINOR 68
+#define LIBAVFILTER_VERSION_MINOR 69
 #define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \