avfilter: add multiband compand filter

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

Changelog

@@ -15,6 +15,7 @@ version <next>:
 - Raw aptX muxer and demuxer
 - NVIDIA NVDEC-accelerated H.264, HEVC, VC1 and VP9 hwaccel decoding
 - Intel QSV-accelerated overlay filter
+- mcompand audio filter
 
 
 version 3.4:

doc/filters.texi

@@ -3270,6 +3270,22 @@ lowpass=c=LFE
 @end example
 @end itemize
 
+@section mcompand
+Multiband Compress or expand the audio's dynamic range.
+
+The input audio is divided into bands using 4th order Linkwitz-Riley IIRs.
+This is akin to the crossover of a loudspeaker, and results in flat frequency
+response when absent compander action.
+
+It accepts the following parameters:
+
+@table @option
+@item args
+This option syntax is:
+attack,decay,[attack,decay..] soft-knee points crossover_frequency [delay [initial_volume [gain]]] | attack,decay ...
+For explanation of each item refer to compand filter documentation.
+@end table
+
 @anchor{pan}
 @section pan
 

libavfilter/Makefile

@@ -101,6 +101,7 @@ OBJS-$(CONFIG_JOIN_FILTER)                   += af_join.o
 OBJS-$(CONFIG_LADSPA_FILTER)                 += af_ladspa.o
 OBJS-$(CONFIG_LOUDNORM_FILTER)               += af_loudnorm.o ebur128.o
 OBJS-$(CONFIG_LOWPASS_FILTER)                += af_biquads.o
+OBJS-$(CONFIG_MCOMPAND_FILTER)               += af_mcompand.o
 OBJS-$(CONFIG_PAN_FILTER)                    += af_pan.o
 OBJS-$(CONFIG_REPLAYGAIN_FILTER)             += af_replaygain.o
 OBJS-$(CONFIG_RESAMPLE_FILTER)               += af_resample.o

libavfilter/allfilters.c

@@ -112,6 +112,7 @@ static void register_all(void)
     REGISTER_FILTER(LADSPA,         ladspa,         af);
     REGISTER_FILTER(LOUDNORM,       loudnorm,       af);
     REGISTER_FILTER(LOWPASS,        lowpass,        af);
+    REGISTER_FILTER(MCOMPAND,       mcompand,       af);
     REGISTER_FILTER(PAN,            pan,            af);
     REGISTER_FILTER(REPLAYGAIN,     replaygain,     af);
     REGISTER_FILTER(RESAMPLE,       resample,       af);

libavfilter/version.h

@@ -30,8 +30,8 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   7
-#define LIBAVFILTER_VERSION_MINOR   0
-#define LIBAVFILTER_VERSION_MICRO 101
+#define LIBAVFILTER_VERSION_MINOR   1
+#define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \