Abstract: A disk player that will play only authorized disks. Predetermined data blocks, including those in the lead-in section of the disk which contain content-related data, are processed to derive an authorization code. The authorization code is stored on the disk in encrypted form, using the private key of a public-key cryptosystem pair. The player processes the same disk data to derive a computed code; the player also uses the paired public key to decrypt the encrypted authorization code on the disk. Play of the disk ensues only if the decrypted authorization code matches the computed code. The same technique can be used to control not play of the disk as a whole, but play in certain specific modes.

Abstract: A system for generating a video signal in a selected one of multiple aspect ratios from play of a disk on which is recorded a motion picture in only one aspect ratio. The disk includes a code indicative of the recorded aspect ratio, and the player has a default aspect ratio setting which can be changed by the user. Typically, the recorded aspect ratio is 16:9, and the player can generate a video signal having any of 16:9, center cut 4:3, pan scan 4:3, and letter box aspect ratios. The player automatically generates the appropriate video signal in accordance with both its default aspect ratio setting and the disk code.