debian 8
#vi /etc/apt/sources.list
将文件里的源都注释掉（前面加#）
deb http://mirrors.163.com/debian/ jessie main
deb-src http://mirrors.163.com/debian/ jessie main

deb http://security.debian.org/ jessie/updates main
deb-src http://security.debian.org/ jessie/updates main

deb http://mirrors.163.com/debian/ jessie-updates main
deb-src http://mirrors.163.com/debian/ jessie-updates main

保存文件。 然后执行 apt-get update && apt-get upgrade
新的稳定的源，可以安装ffmpeg

#163 stable
deb http://mirrors.163.com/debian/ stable main contrib non-free
deb-src http://mirrors.163.com/debian/ stable main contrib non-free
deb http://security.debian.org/ stable/updates main
debian 9
deb http://mirrors.163.com/debian/ stretch main non-free contrib
deb http://mirrors.163.com/debian/ stretch-updates main non-free contrib
deb http://mirrors.163.com/debian/ stretch-backports main non-free contrib
deb-src http://mirrors.163.com/debian/ stretch main non-free contrib
deb-src http://mirrors.163.com/debian/ stretch-updates main non-free contrib
deb-src http://mirrors.163.com/debian/ stretch-backports main non-free contrib
deb http://mirrors.163.com/debian-security/ stretch/updates main non-free contrib
deb-src http://mirrors.163.com/debian-security/ stretch/updates main non-free contrib