Codeina's a nifty little feature of OpenSolaris 2009.06. It's an application from Fluendo that points applications such as Totem or Rhythmbox to Fluendo's web shop if you are missing the codec for the file you are trying to play. In the case of MP3s, the codec is free. For other audio and video formats, you'll have to pay a small license fee.
For example, when I attempt to play an MP3 in Totem, I'm presented with the following:
Clicking Install launches the Codeina Web Shop application where I can register to "buy" the free MP3 decoder:
And then Install the decoder:
Which will quickly complete:
After which my song will automatically start playing.
Note, if Codeina isn't working for you, you may be running into issue Codeina fails to start. The quick fix for this is to remove the Fluendo configuration file and try again.