if your 1640 pro is simular to the 1648/aap pro, then you can do a speed trick to get faster rips.
you can eather use the latest dvddecrypter to rip to harddrive, i get 13x when ripping a dvd r.
or startup cd speed select quality scan set speed to max, click start then when the test starts up stop it. now the speed trick is installed on the drive and will stay there until you open the drive. now rip with dvd shrink.