[root@srv3 bin]# ls -al ffmpeg
-rwxr-xr-x 1 root root 18156848 Mar 30  2013 ffmpeg
[root@srv3 bin]# whereis ffmpeg
ffmpeg: /usr/local/bin/ffmpeg
[root@srv3 bin]# /bin/su -s /bin/sh apache -c "/usr/local/bin/ffmpeg"
/usr/local/bin/ffmpeg: /usr/local/lib/libz.so.1: no version information available (required by /usr/local/bin/ffmpeg)
ffmpeg version N-51456-gb448c0a Copyright (c) 2000-2013 the FFmpeg developers
  built on Mar 30 2013 16:12:05 with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-3)
  configuration: --enable-gpl --enable-libfdk_aac --enable-libmp3lame --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-nonfree
  libavutil      52. 23.100 / 52. 23.100
  libavcodec     55.  2.100 / 55.  2.100
  libavformat    55.  1.100 / 55.  1.100
  libavdevice    55.  0.100 / 55.  0.100
  libavfilter     3. 48.105 /  3. 48.105
  libswscale      2.  2.100 /  2.  2.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  2.100 / 52.  2.100
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'