Whether your 8GB dual layer DVD is incompatible with your DVD player or you simply don't have a blank dual layer disk on hand, converting your 8GB DVD to fit a standard 4GB disc is fairly straightforward. And you won't need to pay for any conversion utilities—there are plenty of free options available for download.
Download and install a free copy of DVDShrink, softpedia.com. Insert your dual layer DVD disc into your computer's CD/DVD-ROM drive, and then launch DVDShrink.
Click on the "Open Disc" option located at the top of the program. Select the drive containing your DVD from the drop-down menu box inside of the Open Disc menu. Click "OK."
Drag the slider, located under the "Compression Settings" tab, to the left to increase the amount of compression that will be applied to your DVD. Drag the slider until the calculated output file size—located above the slider—drops below 4,700MBs.
Click "Backup Disc," back in the main menu, to begin ripping your DVD.
Download and install a free copy of Amok DVD Shrinker, amok.am, insert your dual layer DVD into your Computer's CD/DVD-ROM drive and then launch the program.
Click on the "..." button adjacent to the "Source Path" field, to select the CD/DVD-ROM drive containing the DVD. Click on the "..." button outside of the "Target Path" field to choose a location to save your ripped DVD.
Drag the slider, located next to the "Target Size" field," to set the output DVD's file size below 4.78 GBs.
Click "Transfer" to begin encoding your 8GB DVD into a smaller file size.
Download a free copy of Handbrake, handbrake.fr, install the program and then launch it. Insert your DVD into your computer's CD/DVD-ROM drive.
Click on the "Source" option, and then select your CD/DVD-ROM drive from the list of available sources that appears.
Click "Start" to begin compression your 8GB DVD into MP4 form.