Follow this step..
[root@~]# dnf install epel-release yum-utils -y [root@~]# dnf config-manager --enable epel [root@~]# yum-config-manager --enable powertools [root@~]# dnf install --nogpgcheck https://mirrors.rpmfusion.org/free/el/rpmfusion-free-release-8.noarch.rpm -y [root@~]# dnf install --nogpgcheck https://mirrors.rpmfusion.org/nonfree/el/rpmfusion-nonfree-release-8.noarch.rpm -y [root@~]# dnf update -y [root@~]# dnf install ffmpeg ffmpeg-devel -y