I have intalled Ubuntu 12.04 on my Acer laptop and the problem with the unit of CD/DVD is that it do not reduce the speed of reproduction. In other vertions of Ubuntu this probles was solved with "reduce the speed of the disks when is posible" (or, at least, this option solved the problem for me)but in this vesrsion it is not possible. When I reproduce a DVD picture, the noise of the unit isself and the vibration donẗ allow to hear the sound of the picture. I have tried with VLC reproducer but this is not a solution beause even when I reduce the "speed of reproduction" in the tools of VLC, the sound is distorted but the speed remain the same.
Use this command:
For handling speed of optical drive use eject