CentOS 6&7安装ffmpeg
CentOS 6和7安装方法是不一样的，下面分别说明：
安装前都需要先安装epel扩展源
yum -y install epel-release
centos6
CentOS 6比较简单，安装yum源之后直接安装即可：
su -c 'yum localinstall --nogpgcheck https://download1.rpmfusion.org/free/el/rpmfusion-free-release-6.noarch.rpm https://download1.rpmfusion.org/nonfree/el/rpmfusion-nonfree-release-6.noarch.rpm'
yum -y install ffmpeg ffmpeg-devel
centos7
而CentOS 7需额外安装扩展源：
su -c 'yum localinstall --nogpgcheck https://download1.rpmfusion.org/free/el/rpmfusion-free-release-7.noarch.rpm https://download1.rpmfusion.org/nonfree/el/rpmfusion-nonfree-release-7.noarch.rpm'
rpm --import http://li.nux.ro/download/nux/RPM-GPG-KEY-nux.ro
rpm -Uvh http://li.nux.ro/download/nux/dextop/el7/x86_64/nux-dextop-release-0-1.el7.nux.noarch.rpm
yum -y install ffmpeg ffmpeg-devel