While CD and DVD burning programs, such as K3b, will backup discs, they assume the same size disc for the source and destination. However, most pressed DVDs are in the 8.5GB DVD-9 dual layer format, whereas most recordable discs are 4.7GB DVD-5 single layer discs. Dual layer recordable discs are available, but they are not cheap and some systems have trouble working with them.
The alternative is to compress the DVD you are backing up to fit into a 4.7GB discs. Most DVD-9 discs are not completely full, and they also contain extra items that you may not need on your backup. If you only want to be able to watch the film without risking damaging the original disc, and anyone with children knows this scenario, the main title can be put onto a 4.7 GB disc with a minimal, or no loss of quality.
This is what K9Copy does. It takes a source DVD and fits it onto a DVD-5 disc. It can copy the whole disc, including menus, by transcoding the video files to a lower bit rate. This gives a reduction i theoretical quality although it may not be visible. Alternatively, it will copy one title, which requires a lower reduction in bit rate and even less quality loss. You may also choose which audio tracks to copy, further reducing the amount to be squeezed onto the smaller disc.
If you have two drives, K9Copy will copy directly from one to the others, otherwise it will create n ISO image which it then writes to a blank disc. Tracks can be selected directly in K9Copy's main windows, or there is a wizard that will guide you through the process. K9Copy is also able to encode DVDs to other formats, such as AVI and MP4, but it is in squeezing a dual layer disc's contents onto a single layer disc that it shows you really can get a quart into a pint pot.