iMovie and iDVD compression

[lpmedia]

I've got about 20 gigs worth of footage in iMovie and I need to burn to a DVD.
Obviously, I need to compress the video so it fits on the dvd which is 4.7 gbs.

Should I compress the video in iMovie through quicktime

or

Will iDVD compress the video so it fits onto the DVD?

[twocargar]

You can use the Share menu in iMovie to send your video to iDVD. iDVD will compress it before it burns it. As for how much you can fit on a DVD, see below. -TCG

From http://docs.info.apple.com/article.html?artnum=301557

If you use the Best Performance option in the Encoder Settings section of iDVD Preferences, you can use up to 2 hours of video in your double-layer project. If you select the Best Quality option, you can fit up to 4 hours of video on one Double-Layer DVD. If you wish to burn a single-layer DVD in one of the Double-Layer-supported SuperDrives, select the 4 GB (Single Layer) option in the Project info window in iDVD.