[root@LookBack ~]# which ffmpeg
/usr/local/bin/ffmpeg
[root@LookBack ~]# ffmpeg
ffmpeg version N-75247-g1d2beb6 Copyright (c) 2000-2015 the FFmpeg developers
built with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-16)
configuration: --prefix=/usr/local/ffmpeg_build --extra-cflags=-I/usr/local/ffmpeg_build/include --extra-ldflags=-L/usr/local/ffmpeg_build/lib --bindir=/usr/local/bin --extra-libs=-ldl --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libvpx --enable-libfaac --enable-libmp3lame --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libvo-aacenc --enable-libxvid --disable-ffplay --enable-gpl --enable-postproc --enable-nonfree --enable-avfilter --enable-pthreads
libavutil 55. 2.100 / 55. 2.100
libavcodec 57. 1.100 / 57. 1.100
libavformat 57. 0.100 / 57. 0.100
libavdevice 57. 0.100 / 57. 0.100
libavfilter 6. 1.100 / 6. 1.100
libswscale 4. 0.100 / 4. 0.100
libswresample 2. 0.100 / 2. 0.100
libpostproc 54. 0.100 / 54. 0.100
Hyper fast Audio and Video encoder
usage: ffmpeg [options] [[infile options] -i infile]... {[outfile options] outfile}...
Use -h to get full help or, even better, run 'man ffmpeg'