Comment 7 for bug 225060

You can check that your ffmpeg is ok by adding LD_LIBRARY_PATH:
LD_LIBRARY_PATH=/usr/local/lib ldd /usr/local/bin/ffmpeg

But better to set up the correct links for the shared binaries and rebuild the cache by running command
sudo /sbin/ldconfig -v

You need to install AMR NB and WB development libraries (I assume that codecs libamrb3 and libamrwb3 already installed):
sudo apt-get install libamrnb-dev libamrwb-dev

After that options "enable-libamr_nb" and "enable-libamr_wb" should work.