Fraunhofer FDK AAC codec library. This is currently the highest-quality AAC encoder available with ffmpeg. Requires ffmpeg to be configured with --enable-libfdk_aac (and additionally --enable-nonfree if you're also using --enable-gpl). But beware, it defaults to a low-pass filter of around 14kHz. If you want to preserve higher frequencies, use -cutoff 18000. Adjust the number to the upper frequency limit you prefer.
Ok. Here my own RPM of that library for CentOS 6.5:
Sorry. No time friend. It is not tested. :(