更新源
yum update -y
安装EPEL Release ，因为安装需要使用其他的repo源，所以需要EPEL支持
yum install epel-release -y
如果出现缺少Code提示，可以执行
rpm –-import /etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
查看是否成功导入可以执行
yum repolist
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* base: sjc.edge.kernel.org
* epel: mirrors.sonic.net
* extras: mirror.fileplanet.com
* nux-dextop: mirror.li.nux.ro
* updates: mirror.fileplanet.com
repo id repo name status
!base/7/x86_64 CentOS-7 - Base 10,019
*!epel/x86_64 Extra Packages for Enterprise Linux 7 - x86_64 13,291
!extras/7/x86_64 CentOS-7 - Extras 419
!nux-dextop/x86_64 Nux.Ro RPMs for general desktop use 2,702
!updates/7/x86_64 CentOS-7 - Updates 2,231
repolist: 28,662
导入Code
rpm --import http://li.nux.ro/download/nux/RPM-GPG-KEY-nux.ro
安装Nux-Dextop源
rpm -Uvh http://li.nux.ro/download/nux/dextop/el7/x86_64/nux-dextop-release-0-5.el7.nux.noarch.rpm
然后执行安装即可
yum install ffmpeg