I tried that:
add-apt-repository ppa:kurento/kurento
apt-get update
apt-get install kurento-media-server
and got 404 errors such as:
Err http://ppa.launchpad.net wheezy/main Sources
404 Not Found
Err http://ppa.launchpad.net wheezy/main amd64 Packages
404 Not Found
Ign http://ppa.launchpad.net wheezy/main Translation-fr_FR
Ign http://ppa.launchpad.net wheezy/main Translation-fr
Err http://ubuntu.kurento.org wheezy/main Sources
404 Not Found
Ign http://ppa.launchpad.net wheezy/main Translation-en
Err http://ppa.launchpad.net wheezy/main Sources
404 Not Found
Err http://ppa.launchpad.net wheezy/main amd64 Packages
404 Not Found
Err http://ubuntu.kurento.org wheezy/main amd64 Packages
404 Not Found
Ign http://ppa.launchpad.net wheezy/main Translation-fr_FR
Ign http://ppa.launchpad.net wheezy/main Translation-fr
Ign http://ubuntu.kurento.org wheezy/main Translation-fr_FR
Ign http://ppa.launchpad.net wheezy/main Translation-en
Ign http://ubuntu.kurento.org wheezy/main Translation-fr
Ign http://ubuntu.kurento.org wheezy/main Translation-en
W: Aucune clé publique n'est disponible pour la/les clé(s) suivante(s) :
7638D0442B90D010
W: Aucune clé publique n'est disponible pour la/les clé(s) suivante(s) :
7638D0442B90D010
W: Aucune clé publique n'est disponible pour la/les clé(s) suivante(s) :
9D6D8F6BC857C906
W: Impossible de récupérer http://ppa.launchpad.net/chris-lea/node.js/ubuntu/dists/wheezy/main/source/Sources 404 Not Found
W: Impossible de récupérer http://ppa.launchpad.net/chris-lea/node.js/ubuntu/dists/wheezy/main/binary-amd64/Packages 404 Not Found
W: Impossible de récupérer http://ppa.launchpad.net/kurento/kurento/ubuntu/dists/wheezy/main/source/Sources 404 Not Found
W: Impossible de récupérer http://ppa.launchpad.net/kurento/kurento/ubuntu/dists/wheezy/main/binary-amd64/Packages 404 Not Found
W: Impossible de récupérer http://ubuntu.kurento.org/dists/wheezy/main/source/Sources 404 Not Found
W: Impossible de récupérer http://ubuntu.kurento.org/dists/wheezy/main/binary-amd64/Packages 404 Not Found
Any idea how to install it correctly on Debian server ?
I'm sorry but Kurento only supports trusty version, there are also packages for utopic but as utopic is going to be deprecated soon they will be deprecated as well.
Additionally, you are adding source repositories and kurento repositories do not provide them, source code should be get from github.
Regards.