avfilter: add high-order parametric multiband equalizer filter

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

Changelog

@@ -47,6 +47,7 @@ version <next>:
 - DXVA2-accelerated VP9 decoding
 - SOFAlizer: virtual binaural acoustics filter
 - VAAPI VP9 hwaccel
+- audio high-order multiband parametric equalizer
 
 
 version 2.8:

configure

@@ -2841,6 +2841,7 @@ unix_protocol_select="network"
 
 # filters
 amovie_filter_deps="avcodec avformat"
+anequalizer_filter_deps="cabs cexp"
 aresample_filter_deps="swresample"
 ass_filter_deps="libass"
 asyncts_filter_deps="avresample"

doc/filters.texi

@@ -992,6 +992,100 @@ stream ends. The default value is 2 seconds.
 
 @end table
 
+@section anequalizer
+
+High-order parametric multiband equalizer for each channel.
+
+It accepts the following parameters:
+@table @option
+@item params
+
+This option string is in format:
+"c@var{chn} f=@var{cf} w=@var{w} g=@var{g} t=@var{f} | ..."
+Each equalizer band is separated by '|'.
+
+@table @option
+@item chn
+Set channel number to which equalization will be applied.
+If input doesn't have that channel the entry is ignored.
+
+@item cf
+Set central frequency for band.
+If input doesn't have that frequency the entry is ignored.
+
+@item w
+Set band width in hertz.
+
+@item g
+Set band gain in dB.
+
+@item f
+Set filter type for band, optional, can be:
+
+@table @samp
+@item 0
+Butterworth, this is default.
+
+@item 1
+Chebyshev type 1.
+
+@item 2
+Chebyshev type 2.
+@end table
+@end table
+
+@item curves
+With this option activated frequency response of anequalizer is displayed
+in video stream.
+
+@item size
+Set video stream size. Only useful if curves option is activated.
+
+@item mgain
+Set max gain that will be displayed. Only useful if curves option is activated.
+Setting this to reasonable value allows to display gain which is derived from
+neighbour bands which are too close to each other and thus produce higher gain
+when both are activated.
+
+@item fscale
+Set frequency scale used to draw frequency response in video output.
+Can be linear or logarithmic. Default is logarithmic.
+
+@item colors
+Set color for each channel curve which is going to be displayed in video stream.
+This is list of color names separated by space or by '|'.
+Unrecognised or missing colors will be replaced by white color.
+@end table
+
+@subsection Examples
+
+@itemize
+@item
+Lower gain by 10 of central frequency 200Hz and width 100 Hz
+for first 2 channels using Chebyshev type 1 filter:
+@example
+anequalizer=c0 f=200 w=100 g=-10 t=1|c1 f=200 w=100 g=-10 t=1
+@end example
+@end itemize
+
+@subsection Commands
+
+This filter supports the following commands:
+@table @option
+@item change
+Alter existing filter parameters.
+Syntax for the commands is : "@var{fN}|f=@var{freq}|w=@var{width}|g=@var{gain}"
+
+@var{fN} is existing filter number, starting from 0, if no such filter is available
+error is returned.
+@var{freq} set new frequency parameter.
+@var{width} set new width parameter in herz.
+@var{gain} set new gain parameter in dB.
+
+Full filter invocation with asendcmd may look like this:
+asendcmd=c='4.0 anequalizer change 0|f=200|w=50|g=1',anequalizer=...
+@end table
+
 @section anull
 
 Pass the audio source unchanged to the output.

libavfilter/Makefile

@@ -29,6 +29,7 @@ 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-$(CONFIG_ANEQUALIZER_FILTER)            += af_anequalizer.o
 OBJS-$(CONFIG_AEVAL_FILTER)                  += aeval.o
 OBJS-$(CONFIG_AFADE_FILTER)                  += af_afade.o
 OBJS-$(CONFIG_AFORMAT_FILTER)                += af_aformat.o

libavfilter/allfilters.c

@@ -59,6 +59,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER(ALLPASS,        allpass,        af);
     REGISTER_FILTER(AMERGE,         amerge,         af);
     REGISTER_FILTER(AMIX,           amix,           af);
+    REGISTER_FILTER(ANEQUALIZER,    anequalizer,    af);
     REGISTER_FILTER(ANULL,          anull,          af);
     REGISTER_FILTER(APAD,           apad,           af);
     REGISTER_FILTER(APERMS,         aperms,         af);

libavfilter/version.h

@@ -30,8 +30,8 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   6
-#define LIBAVFILTER_VERSION_MINOR  21
-#define LIBAVFILTER_VERSION_MICRO 101
+#define LIBAVFILTER_VERSION_MINOR  22
+#define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
                                                LIBAVFILTER_VERSION_MINOR, \