Just installed ffmpeg on Ubuntu 12 and tried running it only to see this error?
ffmpeg: error while loading shared libraries: libfdk-aac.so.0: cannot open shared object file: No such file or directory
ffmpeg is looking in the wrong spot for the library you installed. Try this bash command:
ldd `where ffmpeg`
And look for a line like this in the result to confirm the issue:
libfdk-aac.so.0 => not found
How to fix it
Using this additional command fixed my problem.
sudo ldconfig -v
This updates the lists of shared libraries cached in Ubuntu, and now ffmpeg can find that missing shared library.