rpmfusion provides, in addition to other sources yum Fedora and centos source
In the example ffmpeg centos epel-release basis and a source which are not,
But can be found in rpmfusion
RPM Fusion open source on your system
CentOS 6
yum localinstall -y https://download1.rpmfusion.org/free/el/rpmfusion-free-release-6.noarch.rpm
CentOS 7
yum localinstall -y https://download1.rpmfusion.org/free/el/rpmfusion-free-release-7.noarch.rpm
Other centos version please refer rpmfusion official link: https://rpmfusion.org/Configuration