Issues about insalling Cinelerra video editor?

Issues about insalling Cinelerra video editor?

In order to install Cinerella I typed in terminal:
sudo add-apt-repository ppa:cinelerra-ppa/ppa
sudo apt-get update
sudo apt-get install cinelerra
But after last command typed, my computer gives me an error below?
Reading package lists... Done
Building dependency tree      
Reading state information... Done
Package cinelerra is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'cinelerra' has no installation candidate
What should I do (I'm using ubuntu 12.04 Lts)