LOS ANGELES - A new technology from Macrovision Corp. claims to block virtually all known methods for making unauthorized copies of DVDs. The company's RipGuard DVD, launched this week, is designed to thwart cracking programs that get around the encryption system used in standard DVDs. Macrovision also claims a related system to be used with RipGuard can foil attempts to make analog copies of DVDs. Such copies are made by connecting a video recorder to a DVD player's video and audio output jacks, a method that previous DVD copy protection software has failed to prevent fully. Attempts to copy-protect DVDs and CDs have often been plagued by hardware compatibility problems or are easily thwarted using something as simple as a black marker or by holding down the "shift" key while accessing the content. DVDs fitted with the new Macrovision technology do not require new software or hardware to be played and should be compatible with nearly all existing DVD players and DVD computer drives, the company says. Whether Macrovision's new technology works as well as the company promises remains to be seen, said Michael Gartenberg, an analyst with Jupiter Research in New York. "The question is partially how well it works, how compatible it is, and how difficult it will be for somebody to find a way around it, if that's even possible," Gartenberg said. "The more secure you make something like this, the greater risk you run of incompatibility."