If you get package not found, then you will need to add few lines in the yum repository for dag packages installation. Create a file named dag.repo in /etc/yum.repos.d with the following contents on it
[dag]
name=Dag RPM Repository for Red Hat Enterprise Linux
baseurl=http://apt.sw.be/redhat/el$releasever/en/$basearch/dag
gpgcheck=1
enabled=1
From: http://www.mysql-apache-php.com/ffmpeg-install.htm