avfilter: add native headphone spatialization filter

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

Changelog

@@ -19,6 +19,7 @@ version <next>:
 - surround audio filter
 - sofalizer filter switched to libmysofa
 - Gremlin Digital Video demuxer and decoder
+- headphone audio filter
 
 version 3.3:
 - CrystalHD decoder moved to new decode API

doc/filters.texi

@@ -2789,6 +2789,49 @@ Samples where the target gain does not match between channels
 @end table
 @end table
 
+@section headphone
+
+Apply head-related transfer functions (HRTFs) to create virtual
+loudspeakers around the user for binaural listening via headphones.
+The HRIRs are provided via additional streams, for each channel
+one stereo input stream is needed.
+
+The filter accepts the following options:
+
+@table @option
+@item map
+Set mapping of input streams for convolution.
+The argument is a '|'-separated list of channel names in order as they
+are given as additional stream inputs for filter.
+This also specify number of input streams. Number of input streams
+must be not less than number of channels in first stream plus one.
+
+@item gain
+Set gain applied to audio. Value is in dB. Default is 0.
+
+@item type
+Set processing type. Can be @var{time} or @var{freq}. @var{time} is
+processing audio in time domain which is slow.
+@var{freq} is processing audio in frequency domain which is fast.
+Default is @var{freq}.
+
+@item lfe
+Set custom gain for LFE channels. Value is in dB. Default is 0.
+@end table
+
+@subsection Examples
+
+@itemize
+@item
+Full example using wav files as coefficients with amovie filters for 7.1 downmix,
+each amovie filter use stereo file with IR coefficients as input.
+The files give coefficients for each position of virtual loudspeaker:
+@example
+ffmpeg -i input.wav -lavfi-complex "amovie=azi_270_ele_0_DFC.wav[sr],amovie=azi_90_ele_0_DFC.wav[sl],amovie=azi_225_ele_0_DFC.wav[br],amovie=azi_135_ele_0_DFC.wav[bl],amovie=azi_0_ele_0_DFC.wav,asplit[fc][lfe],amovie=azi_35_ele_0_DFC.wav[fl],amovie=azi_325_ele_0_DFC.wav[fr],[a:0][fl][fr][fc][lfe][bl][br][sl][sr]headphone=FL|FR|FC|LFE|BL|BR|SL|SR"
+output.wav
+@end example
+@end itemize
+
 @section highpass
 
 Apply a high-pass filter with 3dB point frequency.

libavfilter/Makefile

@@ -92,6 +92,7 @@ OBJS-$(CONFIG_EXTRASTEREO_FILTER)            += af_extrastereo.o
 OBJS-$(CONFIG_FIREQUALIZER_FILTER)           += af_firequalizer.o
 OBJS-$(CONFIG_FLANGER_FILTER)                += af_flanger.o generate_wave_table.o
 OBJS-$(CONFIG_HDCD_FILTER)                   += af_hdcd.o
+OBJS-$(CONFIG_HEADPHONE_FILTER)              += af_headphone.o
 OBJS-$(CONFIG_HIGHPASS_FILTER)               += af_biquads.o
 OBJS-$(CONFIG_JOIN_FILTER)                   += af_join.o
 OBJS-$(CONFIG_LADSPA_FILTER)                 += af_ladspa.o

libavfilter/allfilters.c

@@ -105,6 +105,7 @@ static void register_all(void)
     REGISTER_FILTER(FIREQUALIZER,   firequalizer,   af);
     REGISTER_FILTER(FLANGER,        flanger,        af);
     REGISTER_FILTER(HDCD,           hdcd,           af);
+    REGISTER_FILTER(HEADPHONE,      headphone,      af);
     REGISTER_FILTER(HIGHPASS,       highpass,       af);
     REGISTER_FILTER(JOIN,           join,           af);
     REGISTER_FILTER(LADSPA,         ladspa,         af);

libavfilter/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   6
-#define LIBAVFILTER_VERSION_MINOR  91
+#define LIBAVFILTER_VERSION_MINOR  92
 #define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \