If your files are that big I'd say its a retail DVD rip, that around where they run and you would need dual-layer for that. If its a .avi file or something of the sort there are programs to convert it into a format to play on a DVD player, in which case it should run around a 4.1gb ISO. You can't just put a video file on a blank disc and expect it to play, you need to convert it into a proper DVD format of some sort of disc image. If your looking at copying entire retail DVDs *cough pirate...* then you'd need Dual Layer discs, they cost more but get the job done and you wouldn't have to cut anything out then.