If you need to build your ffmpeg for the real-time audio/video streaming (e.g. for VoIP, video-chat, live-TV), you can use Opus audio codec in the combination with x264 video codec, to get the best from both worlds.
Follow these steps before you attempt to compile your FFmpeg:
In order to quickly compile your FFmpeg with the support for libraries libopus and libx264, you can type the following commands in your shell:
$ cd /my/path/where/i/keep/compiled/stuff $ git clone git://source.ffmpeg.org/ffmpeg.git $ cd ffmpeg $ ./configure --enable-gpl --enable-libx264 --enable-libopus $ make # make install
P.S. If you are using Ubuntu, you'll most probably have to use sudo for the last command, like:
$ sudo make install