ISO files are images of CDs or DVDs, file versions of the complete contents of a disk. Though some people back up their personal movies as ISO files, there are some advantages to converting these movies to AVI format. AVIs can take up significantly less hard drive space and can be played by most portable video devices. The process for creating an AVI from an ISO is the same as creating one directly from a DVD. This process is called DVD ripping, and it is quite easy in Ubuntu, thanks to the DVD::Rip application.
Type "sudo apt-get install dvdrip" into the terminal to install DVD::Rip.
Start DVD::Rip from the Applications > Sound & Video menu, or from the terminal by typing "dvdrip." The Preferences window should open automatically; otherwise hit Ctrl+P.
Set your DVD-ROM device under "Default DVD Device," then open the "Miscellaneous Options" tab. Set the "Default Container Format" to "AVI," and click "OK" to close the Preferences window.
Under "Data Source Selection," click "Choose DVD Image Directory," and browse to the ISO image you wish to convert. If you wish to select extra options such as resizing the video or including subtitles, explore the other tabs in this main window. When you are finished, go to the "Transcode" tab.
Set final transcoding options in the "Transcode" tab. Though most of the defaults should be fine, you may want to set the target file size yourself. When you are ready, hit "Transcode," and come back in a few minutes for your completed AVI file.
If you want to convert encrypted DVD ISOs to AVI, you will have to install libdvdread3 as well.
Copying CDs or DVDs without permission is a violation of copyright law. Ensure that you have appropriate permission before attempting to copy a commercial disc.