ffmpeg -i 6.2.mov -vn -ab 92k -acodec aac -strict -2 try.m4a

ffmpeg version 2.5 Copyright (c) 2000-2014 the FFmpeg developers
built on Dec 20 2014 09:33:55 with Apple LLVM version 6.0 (clang-600.0.56) (based on LLVM 3.5svn)
configuration: --prefix=/usr/local/Cellar/ffmpeg/2.5 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-libx264 --enable-libmp3lame --enable-libxvid --enable-libvo-aacenc --enable-libfdk-aac --enable-nonfree --enable-vda
libavutil      54. 15.100 / 54. 15.100
libavcodec     56. 13.100 / 56. 13.100
libavformat    56. 15.102 / 56. 15.102
libavdevice    56.  3.100 / 56.  3.100
libavfilter     5.  2.103 /  5.  2.103
libavresample   2.  1.  0 /  2.  1.  0
libswscale      3.  1.101 /  3.  1.101
libswresample   1.  1.100 /  1.  1.100
libpostproc    53.  3.100 / 53.  3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '6.2.mov':
Metadata:
 major_brand     : qt
 minor_version   : 0
 compatible_brands: qt
 creation_time   : 2014-12-03 10:12:08
Duration: 00:00:01.58, start: 0.000000, bitrate: 42754 kb/s
Stream #0:0(und): Video: prores (apcn / 0x6E637061), yuv422p10le(bt709), 960x540, 40383 kb/s, SAR 1:1 DAR 16:9, 23.98 fps, 23.98 tbr, 24k tbn, 24k tbc (default)
 Metadata:
  creation_time   : 2014-12-03 10:12:08
  handler_name    : Core Media Data Handler
  encoder         : Apple ProRes 422
  timecode        : 00:00:00:00
 Stream #0:1(und): Audio: pcm_s24le (in24 / 0x34326E69), 48000 Hz, stereo, s32 (24 bit), 2304 kb/s (default)
 Metadata:
  creation_time   : 2014-12-03 10:12:08
  handler_name    : Core Media Data Handler
 Stream #0:2(und): Data: none (tmcd / 0x64636D74), 0 kb/s (default)
 Metadata:
  creation_time   : 2014-12-03 10:12:08
  handler_name    : Core Media Data Handler
  timecode        : 00:00:00:00
File 'try.m4a' already exists. Overwrite ? [y/N] y
Output #0, ipod, to 'try.m4a':
Metadata:
 major_brand     : qt
 minor_version   : 0
 compatible_brands: qt
 encoder         : Lavf56.15.102
 Stream #0:0(und): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp (24 bit), 92 kb/s (default)
 Metadata:
  creation_time   : 2014-12-03 10:12:08
  handler_name    : Core Media Data Handler
  encoder         : Lavc56.13.100 aac
 Stream mapping:
 Stream #0:1 -> #0:0 (pcm_s24le (native) -> aac (native))
 Press [q] to stop, [?] for help
 size=      19kB time=00:00:01.60 bitrate=  97.9kbits/s
 video:0kB audio:18kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 5.684210%