一、安装前都需要先安装epel扩展源
yum -y install epel-release
二、对于6，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
三、在centos7中安装如下：
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
ps:在php中执行音频转换时，如果报错，报错信息如：
ffmpeg: error while loading shared libraries: libavdevice.so.52: cannot open shared object file: No such file or directory
则需要在配置文件中增加：（配置文件为：/etc/ld.so.conf）
/usr/lib
/usr/local/lib
即可