ffmpeg: error while loading shared libraries: libavdevice.so.54

You will get errors when attempting to convert the videos OR when verifying the FFmpeg version.
error occurring when loading shared libraries for ffmpeg The shared object file libavdevice.so.54 cannot be opened: There is no such directory or file.

This is a result of corrupt ffmpeg, which was compiled by hand. All you have to do is recompile ffmpeg, and the error message will disappear.

Login to your server via SSH.
# cd /usr/local/src/ffmpeg-0.xx.x
# ./configure
# make
# make install

Performing the above steps will recompile ffmpeg on your dedicated server. Good to go ahead and convert videos now.