Building FFmpeg on CentOS:
1. Update and install build environment:
yum update
yum install make automake autoconf libtool gcc-c++
2. Install YASM:
cd /tmp
wget http://pkgs.repoforge.org/yasm/yasm-1.1.0-1.el5.rf.x86_64.rpm
rpm -ivh yasm-1.1.0-1.el6.rf.x86_64.rpm