Symptoms
Any attempt to play video will result in an error:
Movie Player requires additional plugins to decode this file. The following plugins are required : MPEG-4-AAC decoder and H.264 decoder

The offered help for search also fails.
Solution
Use below command to install all necessary multimedia plugins and codes from nux-dextop repository:
# yum -y install http://li.nux.ro/download/nux/dextop/el7/x86_64/nux-dextop-release-0-5.el7.nux.noarch.rpm # yum install libdvdcss gstreamer{,1}-plugins-ugly gstreamer-plugins-bad-nonfree gstreamer1-plugins-bad-freeworld libde265 x265
Furthermore, if your default multimedia application still fails to play your video try some other media players such us smplayer or vlc. You can now install these media players by the following linux command:
# yum install vlc smplayer