If you don't want to add the repository, you can install the package by opening a terminal in the directory where you have downloaded Opera, and run this command: Note!Unfortunately, Opera has some issues with using the library sometimes, because it's so tightly integrated with chromium.
The library that provides many codecs that Opera uses is called ffmpeg.
However, they have removed the H.264 part of it, because even though ffmpeg has a free license, the patent pool of H.264 will demand license fees from commercial projects that are using implementations of it, like Opera.
Chromium and Chrome, however, do have support for H.264 in their ffmpeg library, because Google has payed the license.
Up to version 12, Opera made their own engine for Opera, called Presto.
But in 2013, they decided to re-create the browser from scratch, built on Chromium with the Blink engine.
The first version of the "new Opera" was Opera 15, and the "old Opera" was discontinued.But as the new browser was built from scratch, it lost many features.Therefore, there are still many users that want to use Opera 12.As it differs very much, there's a second wiki page for that version. The best and easiest way to install Opera is by just downloading the deb-package from Opera's website.When you install the package, it will add their repository, automatically configured for updates.When you have downloaded the file, you can install it by double clicking on the file to open Ubuntu software center.