[FFmpeg-user] Unable to encode to 7.1 ALAC

[Rashed]

Hi,

I am trying to create 7.1 ALAC using 8 channel wav file as input. But
output is always 6.1 instead of 7.1.

Need help in fixing this issue.

stdout:

ffmpeg version N-69146-g90c9899 Copyright (c) 2000-2015 the FFmpeg
developers
  built on Jan 19 2015 01:28:38 with gcc 4.9.2 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads
--enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r
--enable-gn
utls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b
--enable-libcaca --enable-libfreetype --enable-libgme --enable-libgsm
--enabl
e-libilbc --enable-libmodplug --enable-libmp3lame
--enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg
--enable-libopus --enabl
e-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex
--enable-libtheora --enable-libtwolame --enable-libvidstab
--enable-libvo-aacen
c --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx
--enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265
--enable-libxavs
--enable-libxvid --enable-lzma --enable-decklink --enable-zlib
  libavutil      54. 17.100 / 54. 17.100
  libavcodec     56. 20.100 / 56. 20.100
  libavformat    56. 19.100 / 56. 19.100
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5.  8.100 /  5.  8.100
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  3.100 / 53.  3.100
Guessed Channel Layout for  Input Stream #0.0 : 7.1
Input #0, wav, from '71ch_16bit_48khz_pcm.wav':
  Duration: 00:01:30.49, bitrate: 6144 kb/s
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 48000 Hz, 8
channels, s16, 6144 kb/s
Output #0, ipod, to 'output.m4a':
  Metadata:
    encoder         : Lavf56.19.100
    Stream #0:0: Audio: alac (alac / 0x63616C61), 48000 Hz, 6.1, s16p, 128
kb/s
    Metadata:
      encoder         : Lavc56.20.100 alac
Stream mapping:
  Stream #0:0 -> #0:0 (pcm_s16le (native) -> alac (native))
Press [q] to stop, [?] for help
size=   19371kB time=00:01:30.53 bitrate=1752.7kbits/s
video:0kB audio:19366kB subtitle:0kB other streams:0kB global headers:0kB
muxing overhead: 0.026438%


Thanks,
Rashed