ffmpeg -i "Tetris.aac" -acodec copy -y "Doctor P - Tetris.m4a"
ffmpeg version N-69672-g078be09 Copyright (c) 2000-2015 the FFmpeg developers
  built with gcc 4.9.2 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-av
isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enab
le-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --
enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-lib
modplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrw
b --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinge
r --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --en
able-libvidstab --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis
 --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-
libx265 --enable-libxavs --enable-libxvid --enable-lzma --enable-decklink --enab
le-zlib
  libavutil      54. 18.100 / 54. 18.100
  libavcodec     56. 21.102 / 56. 21.102
  libavformat    56. 19.100 / 56. 19.100
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5.  9.104 /  5.  9.104
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  3.100 / 53.  3.100
[aac @ 0000000002c0fc20] Estimating duration from bitrate, this may be inaccurat
e
Input #0, aac, from 'Tetris.aac':
  Duration: 00:06:48.84, bitrate: 143 kb/s
    Stream #0:0: Audio: aac (LC), 44100 Hz, stereo, fltp, 143 kb/s
Output #0, ipod, to 'Doctor P - Tetris.m4a':
  Metadata:
    encoder         : Lavf56.19.100
    Stream #0:0: Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo, 143 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
[ipod @ 0000000002ca6940] Malformed AAC bitstream detected: use the audio bitstr
eam filter 'aac_adtstoasc' to fix it ('-bsf:a aac_adtstoasc' option with ffmpeg)

av_interleaved_write_frame(): Operation not permitted
size=       0kB time=00:00:00.02 bitrate=  87.5kbits/s
video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing ove
rhead: 1853.846191%
Conversion failed!