C:\>ffmpeg.exe -i input.aac -acodec copy -f adts output.aac
ffmpeg version N-36193-gf514695, Copyright (c) 2000-2011 the FFmpeg developers
  built on Dec 26 2011 17:50:37 with gcc 4.6.2
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-ru
ntime-cpudetect --enable-avisynth --enable-bzlib --enable-frei0r --enable-libope
ncore-amrnb --enable-libopencore-amrwb --enable-libfreetype --enable-libgsm --en
able-libmp3lame --enable-libopenjpeg --enable-librtmp --enable-libschroedinger -
-enable-libspeex --enable-libtheora --enable-libvo-aacenc --enable-libvo-amrwben
c --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs --enable-
libxvid --enable-zlib
  libavutil      51. 33.100 / 51. 33.100
  libavcodec     53. 48.100 / 53. 48.100
  libavformat    53. 28.100 / 53. 28.100
  libavdevice    53.  4.100 / 53.  4.100
  libavfilter     2. 54.100 /  2. 54.100
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0.  5.100 /  0.  5.100
  libpostproc    51.  2.100 / 51.  2.100
[aac_latm @ 01CB9020] audio config changed
[loas @ 01CB8740] max_analyze_duration 5000000 reached at 5013333
[loas @ 01CB8740] Estimating duration from bitrate, this may be inaccurate
Input #0, loas, from 'input.aac':
  Duration: N/A, bitrate: N/A
    Stream #0:0: Audio: aac_latm, 48000 Hz, stereo, s16
Output #0, adts, to 'output.aac':
  Metadata:
    encoder         : Lavf53.28.100
    Stream #0:0: Audio: aac_latm, 48000 Hz, stereo
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
size=    3607kB time=00:03:46.21 bitrate= 130.6kbits/s
video:0kB audio:3535kB global headers:0kB muxing overhead 2.050777%