lavfi: add aeval filter

Changelog

@@ -12,6 +12,7 @@ version <next>
 - complete Voxware MetaSound decoder
 - remove mp3_header_compress bitstream filters
 - Windows resource files for shared libraries
+- aeval filter
 
 
 version 2.1:

doc/filters.texi

@@ -435,6 +435,70 @@ aecho=0.8:0.9:1000|1800:0.3|0.25
 @end example
 @end itemize
 
+@section aeval
+
+Modify an audio signal according to the specified expressions.
+
+This filter accepts one or more expressions (one for each channel),
+which are evaluated and used to modify a corresponding audio signal.
+
+This filter accepts the following options:
+
+@table @option
+@item exprs
+Set the '|'-separated expressions list for each separate channel. If
+the number of input channels is greater than the number of
+expressions, the last specified expression is used for the remaining
+output channels.
+
+@item channel_layout, c
+Set output channel layout. If not specified, the channel layout is
+specified by the number of expressions. If set to @samp{same}, it will
+use by default the same input channel layout.
+@end table
+
+Each expression in @var{exprs} can contain the following constants and functions:
+
+@table @option
+@item ch
+channel number of the current expression
+
+@item n
+number of the evaluated sample, starting from 0
+
+@item s
+sample rate
+
+@item t
+time of the evaluated sample expressed in seconds
+
+@item nb_in_channels
+@item nb_out_channels
+input and output number of channels
+
+@item val(CH)
+the value of input channel with number @var{CH}
+@end table
+
+Note: this filter is slow. For faster processing you should use a
+dedicated filter.
+
+@subsection Examples
+
+@itemize
+@item
+Half volume:
+@example
+aeval=val(ch)/2:c=same
+@end example
+
+@item
+Invert phase of the second channel:
+@example
+eval=val(0)|-val(1)
+@end example
+@end itemize
+
 @section afade
 
 Apply fade-in/out effect to input audio.

libavfilter/Makefile

@@ -53,6 +53,7 @@ OBJS-$(CONFIG_AVCODEC)                       += avcodec.o
 OBJS-$(CONFIG_ACONVERT_FILTER)               += af_aconvert.o
 OBJS-$(CONFIG_ADELAY_FILTER)                 += af_adelay.o
 OBJS-$(CONFIG_AECHO_FILTER)                  += af_aecho.o
+OBJS-$(CONFIG_AEVAL_FILTER)                  += asrc_aevalsrc.o
 OBJS-$(CONFIG_AFADE_FILTER)                  += af_afade.o
 OBJS-$(CONFIG_AFORMAT_FILTER)                += af_aformat.o
 OBJS-$(CONFIG_AINTERLEAVE_FILTER)            += f_interleave.o

libavfilter/allfilters.c

@@ -50,6 +50,7 @@ void avfilter_register_all(void)
 #endif
     REGISTER_FILTER(ADELAY,         adelay,         af);
     REGISTER_FILTER(AECHO,          aecho,          af);
+    REGISTER_FILTER(AEVAL,          aeval,          af);
     REGISTER_FILTER(AFADE,          afade,          af);
     REGISTER_FILTER(AFORMAT,        aformat,        af);
     REGISTER_FILTER(AINTERLEAVE,    ainterleave,    af);

libavfilter/version.h

@@ -30,8 +30,8 @@
 #include "libavutil/avutil.h"
 
 #define LIBAVFILTER_VERSION_MAJOR  3
-#define LIBAVFILTER_VERSION_MINOR  91
-#define LIBAVFILTER_VERSION_MICRO 101
+#define LIBAVFILTER_VERSION_MINOR  92
+#define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \