A progress dialog indicates how far along you are in creating the DVD. You can click the Cancel button at any point before the burning stage to quit and leave the DVD disc untouched.
iDVD burns the disc in whatever format (NTSC or PAL) you have specified in iDVD preferences, regardless of which format the video is in. If the formats are different, iDVD warns you before burning, because some visual distortions might result in the burned DVD.
Note: After burning, to eject a disc from your computer’s internal disc drive, press the Media Eject key on your keyboard, if there is one. On keyboards with no Media Eject key, hold down the F12 key until the eject icon appears and your disc is ejected.
Go to Mac Help for more options for ejecting discs.