Abstract: Generally the more effective is the copy protection provided on an optical disc, such as a DVD, the greater is the likelihood that the copy protection will adversely interfere with legitimate uses of the optical disc. It is therefore proposed to include at least one region of subversive data within the content in the data area of an optical disc, and then to prevent access to each such region of subversive data during normal playback of the disc. For a DVD, the subversive data may be incorporated within video objects and/or may be in gaps between files in the DVD_Video zone. It is arranged that there are no navigable paths to the regions of subversive data.

Abstract: A codeword and a method for generating a codeword is provided. The codeword may be used in error correction of digital optical media and DVDs, the codeword having a plurality of data symbols and a plurality of parity symbols, and includes an augmented channel word which can be read as either a first value or a second alternate value. The augmented channel word is one of the plurality of data and parity symbols, the augmented channel word retaining its value irrespective of any error correction performed.