avfilter: add audio emphasis filter

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

Changelog

@@ -40,6 +40,7 @@ version <next>:
 - apulsator filter
 - sidechaingate audio filter
 - mipsdspr1 option has been renamed to mipsdsp
+- aemphasis filter
 
 
 version 2.8:

configure

@@ -1051,6 +1051,21 @@ int main(void){ $func(); }
 EOF
 }
 
+check_complexfunc(){
+    log check_complexfunc "$@"
+    func=$1
+    narg=$2
+    shift 2
+    test $narg = 2 && args="f, g" || args="f * I"
+    disable $func
+    check_ld "cc" "$@" <<EOF && enable $func
+#include <complex.h>
+#include <math.h>
+float foo(complex float f, complex float g) { return $func($args); }
+int main(void){ return (int) foo; }
+EOF
+}
+
 check_mathfunc(){
     log check_mathfunc "$@"
     func=$1
@@ -1768,6 +1783,11 @@ INTRINSICS_LIST="
     intrinsics_neon
 "
 
+COMPLEX_FUNCS="
+    cabs
+    cexp
+"
+
 MATH_FUNCS="
     atanf
     atan2f
@@ -1903,6 +1923,7 @@ HAVE_LIST="
     $ARCH_FEATURES
     $ATOMICS_LIST
     $BUILTIN_LIST
+    $COMPLEX_FUNCS
     $HAVE_LIST_CMDLINE
     $HAVE_LIST_PUB
     $HEADERS_LIST
@@ -2785,6 +2806,7 @@ unix_protocol_deps="sys_un_h"
 unix_protocol_select="network"
 
 # filters
+aemphasis_filter_deps="cabs cexp"
 amovie_filter_deps="avcodec avformat"
 aresample_filter_deps="swresample"
 ass_filter_deps="libass"
@@ -5324,6 +5346,10 @@ for func in $MATH_FUNCS; do
     eval check_mathfunc $func \${${func}_args:-1}
 done
 
+for func in $COMPLEX_FUNCS; do
+    eval check_complexfunc $func \${${func}_args:-1}
+done
+
 # these are off by default, so fail if requested and not available
 enabled avfoundation_indev && { check_header_oc AVFoundation/AVFoundation.h || disable avfoundation_indev; }
 enabled avfoundation_indev && { check_lib2 CoreGraphics/CoreGraphics.h CGGetActiveDisplayList -framework CoreGraphics ||

doc/filters.texi

@@ -528,6 +528,52 @@ aecho=0.8:0.9:1000|1800:0.3|0.25
 @end example
 @end itemize
 
+@section aemphasis
+Audio emphasis filter creates or restores material directly taken from LPs or
+emphased CDs with different filter curves. E.g. to store music on vinyl the
+signal has to be altered by a filter first to even out the disadvantages of
+this recording medium.
+Once the material is played back the inverse filter has to be applied to
+restore the distortion of the frequency response.
+
+The filter accepts the following options:
+
+@table @option
+@item level_in
+Set input gain.
+
+@item level_out
+Set output gain.
+
+@item mode
+Set filter mode. For restoring material use @code{reproduction} mode, otherwise
+use @code{production} mode. Default is @code{reproduction} mode.
+
+@item type
+Set filter type. Selects medium. Can be one of the following:
+
+@table @option
+@item col
+select Columbia.
+@item emi
+select EMI.
+@item bsi
+select BSI (78RPM).
+@item riaa
+select RIAA.
+@item cd
+select Compact Disc (CD).
+@item 50fm
+select 50µs (FM).
+@item 75fm
+select 75µs (FM).
+@item 50kf
+select 50µs (FM-KF).
+@item 75kf
+select 75µs (FM-KF).
+@end table
+@end table
+
 @section aeval
 
 Modify an audio signal according to the specified expressions.

libavfilter/Makefile

@@ -27,6 +27,7 @@ OBJS-$(CONFIG_ACOMPRESSOR_FILTER)            += af_sidechaincompress.o
 OBJS-$(CONFIG_ACROSSFADE_FILTER)             += af_afade.o
 OBJS-$(CONFIG_ADELAY_FILTER)                 += af_adelay.o
 OBJS-$(CONFIG_AECHO_FILTER)                  += af_aecho.o
+OBJS-$(CONFIG_AEMPHASIS_FILTER)              += af_aemphasis.o
 OBJS-$(CONFIG_AEVAL_FILTER)                  += aeval.o
 OBJS-$(CONFIG_AFADE_FILTER)                  += af_afade.o
 OBJS-$(CONFIG_AFORMAT_FILTER)                += af_aformat.o

libavfilter/allfilters.c

@@ -49,6 +49,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER(ACROSSFADE,     acrossfade,     af);
     REGISTER_FILTER(ADELAY,         adelay,         af);
     REGISTER_FILTER(AECHO,          aecho,          af);
+    REGISTER_FILTER(AEMPHASIS,      aemphasis,      af);
     REGISTER_FILTER(AEVAL,          aeval,          af);
     REGISTER_FILTER(AFADE,          afade,          af);
     REGISTER_FILTER(AFORMAT,        aformat,        af);

libavfilter/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   6
-#define LIBAVFILTER_VERSION_MINOR  19
+#define LIBAVFILTER_VERSION_MINOR  20
 #define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \