[centos7] [firefox] to play video, you need to install the required video codecs

[solution] : need to install ffmpeg

Total 4 steps:

Step 1: sudo yum install ffmpeg ffmpeg-devel

Step 2: sudo rpm -v --import http://li.nux.ro/download/nux/RPM-GPG-KEY-nux.ro
Step 3: sudo rpm -Uvh http://li.nux.ro/download/nux/dextop/el7/x86_64/nux-dextop-release-0-5.el7.nux.noarch.rpm

Step4: sudo yum install ffmpeg ffmpeg-devel