iDVD '09 (7.x): Burning to a DVD+R DL (Double Layer) disc
Newer SuperDrive optical drives in Macintosh computers can burn discs in DVD+R DL (Double Layer) format. Double-layer discs store almost twice as much content as single-layer discs, making them a great choice for large projects.
To see whether your computer’s SuperDrive can burn DVD+R DL discs, choose Project > Project Info. If you see 8.0 GB (Double Layer) in the DVD Type pop-up menu, you can use DVD+R DL discs for your project.
To burn a project to a DVD+R DL disc:
With the finished project open in iDVD, choose Project > Project Info and then choose Double Layer (DL) from the DVD Type pop-up menu.
Select the encoder setting you want to use. If you have more than 120 minutes of content, select High Quality.
Click the Burn button (shown below).
When prompted, insert a DVD+R DL disc into the drive.
You can use your internal SuperDrive or an external third-party drive.
If the disc isn’t blank, iDVD asks whether you want to erase the disc.
If your project is small enough to fit on a single-layer disc and you insert a double-layer disc, you see a dialog giving you the option to change the media type. You can cancel the burn and start again, or insert a single-layer disc and continue.
You should always burn double-layer discs directly from iDVD and not from a disc image. Double-layer discs burned from a disc image may cause playback issues in some DVD players, such as freezing during playback.