lavfi: add aresample filter

Based on a patch by Stefano.
Signed-off-by: Stefano Sabatini <stefano.sabatini-lala@poste.it>

doc/filters.texi

@@ -124,6 +124,19 @@ aformat=s16:mono\\,stereo:all
 
 Pass the audio source unchanged to the output.
 
+@section aresample
+
+Resample the input audio to the specified sample rate.
+
+The filter accepts exactly one parameter, the output sample rate. If not
+specified then the filter will automatically convert between its input
+and output sample rates.
+
+For example, to resample the input audio to 44100Hz:
+@example
+aresample=44100
+@end example
+
 @c man end AUDIO FILTERS
 
 @chapter Audio Sources

libavfilter/Makefile

@@ -2,6 +2,7 @@ include $(SUBDIR)../config.mak
 
 NAME = avfilter
 FFLIBS = avutil
+FFLIBS-$(CONFIG_ARESAMPLE_FILTER) += avcodec
 FFLIBS-$(CONFIG_MOVIE_FILTER) += avformat avcodec
 FFLIBS-$(CONFIG_SCALE_FILTER) += swscale
 FFLIBS-$(CONFIG_MP_FILTER) += avcodec
@@ -20,6 +21,7 @@ OBJS-$(CONFIG_AVCODEC)                       += avcodec.o
 
 OBJS-$(CONFIG_AFORMAT_FILTER)                += af_aformat.o
 OBJS-$(CONFIG_ANULL_FILTER)                  += af_anull.o
+OBJS-$(CONFIG_ARESAMPLE_FILTER)              += af_aresample.o
 
 OBJS-$(CONFIG_ANULLSRC_FILTER)               += asrc_anullsrc.o
 

libavfilter/allfilters.c

@@ -36,6 +36,7 @@ void avfilter_register_all(void)
 
     REGISTER_FILTER (AFORMAT,     aformat,     af);
     REGISTER_FILTER (ANULL,       anull,       af);
+    REGISTER_FILTER (ARESAMPLE,   aresample,   af);
 
     REGISTER_FILTER (ANULLSRC,    anullsrc,    asrc);
 

libavfilter/avfilter.h

@@ -29,8 +29,8 @@
 #include "libavutil/rational.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  2
-#define LIBAVFILTER_VERSION_MINOR 31
-#define LIBAVFILTER_VERSION_MICRO  1
+#define LIBAVFILTER_VERSION_MINOR 32
+#define LIBAVFILTER_VERSION_MICRO  0
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \