[FFmpeg-trac] #7632(avfilter:new): SOFAlizer not centering the center channel

[FFmpeg]

#7632: SOFAlizer not centering the center channel
-------------------------------------+-------------------------------------
             Reporter:               |                     Type:  defect
  StarBrilliant                      |                 Priority:  normal
               Status:  new          |                  Version:  git-
            Component:  avfilter     |  master
             Keywords:  sofa,        |               Blocked By:
  sofalizer, hrtf                    |  Reproduced by developer:  0
             Blocking:               |
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:

 I created a 1000Hz -18dBFS beeping tone on the FC channel and pass it to
 SOFAlizer with [https://github.com/videolan/vlc/tree/master/share/hrtfs
 dodeca_and_7channel_3DSL_HRTF.sofa] (built-in HRTF file of VLC player).

 The resulting audio has a left channel at -32dBFS, and a right channel at
 between -34 and -33dBFS.

 Since the file is extracted from VLC, the HRTF filter included in VLC is
 working and fine (except for a weird series of operation is necessary to
 enable it), I doubt the problem is on FFmpeg's side.

 I tested with other HRTF files such as [https://github.com/sofacoustics
 /SOFAlizer-for-Unity hrtf1.sofa] (built-in HRTF file of SOFAlizer for
 Unity plugin), left=-40dBFS, right=-38dBFS. So the bias sometimes goes
 left and sometimes goes right.

 How to reproduce:
 {{{
 % ./Downloads/ffmpeg-20181218-3a36b0c-macos64-static/bin/ffmpeg
 -filter_complex
 "sine=f=1000:r=48000:d=10,aeval=0|0|val(0)|0|0|0:c=5.1,aformat=channel_layouts=5.1,asplit[5.1][TEMP];[TEMP]sofalizer=sofa=./Downloads/dodeca_and_7channel_3DSL_HRTF.sofa:gain=15:lfegain=9[SOFA]"
 -map "[5.1]" 5.1.wav -map "[SOFA]" sofa.wav
 ffmpeg version N-92738-g3a36b0c4b8 Copyright (c) 2000-2018 the FFmpeg
 developers
   built with Apple LLVM version 10.0.0 (clang-1000.11.45.5)
   configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-
 fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-
 libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-
 amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus
 --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora
 --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp
 --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg
 --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-
 libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex
 --enable-libxvid --enable-libaom --enable-appkit --enable-avfoundation
 --enable-coreimage --enable-audiotoolbox
   libavutil      56. 24.101 / 56. 24.101
   libavcodec     58. 42.104 / 58. 42.104
   libavformat    58. 24.101 / 58. 24.101
   libavdevice    58.  6.101 / 58.  6.101
   libavfilter     7. 46.101 /  7. 46.101
   libswscale      5.  4.100 /  5.  4.100
   libswresample   3.  4.100 /  3.  4.100
   libpostproc    55.  4.100 / 55.  4.100
 }}}
 Patches should be submitted to the ffmpeg-devel mailing list and not this
 bug tracker.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/7632>
FFmpeg <https://ffmpeg.org>
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